__init__.py

# Deliberately use "from dataclasses import *".  Every name in __all__
# is tested, so they all must be present.  This is a way to catch
# missing ones.

from dataclasses import *

import abc
import io
import pickle
import inspect
import builtins
import types
import weakref
import traceback
import unittest
from unittest.mock import Mock
from typing import ClassVar, Any, List, Union, Tuple, Dict, Generic, TypeVar, Optional, Protocol, DefaultDict
from typing import get_type_hints
from collections import deque, OrderedDict, namedtuple, defaultdict
from functools import total_ordering

import typing       # Needed for the string "typing.ClassVar[int]" to work as an annotation.
import dataclasses  # Needed for the string "dataclasses.InitVar[int]" to work as an annotation.

from test import support

# Just any custom exception we can catch.
class CustomError(Exception): pass

class TestCase(unittest.TestCase):
    def test_no_fields(self):
        @dataclass
        class C:
            pass

        o = C()
        self.assertEqual(len(fields(C)), 0)

    def test_no_fields_but_member_variable(self):
        @dataclass
        class C:
            i = 0

        o = C()
        self.assertEqual(len(fields(C)), 0)

    def test_one_field_no_default(self):
        @dataclass
        class C:
            x: int

        o = C(42)
        self.assertEqual(o.x, 42)

    def test_field_default_default_factory_error(self):
        msg = "cannot specify both default and default_factory"
        with self.assertRaisesRegex(ValueError, msg):
            @dataclass
            class C:
                x: int = field(default=1, default_factory=int)

    def test_field_repr(self):
        int_field = field(default=1, init=True, repr=False)
        int_field.name = "id"
        repr_output = repr(int_field)
        expected_output = "Field(name='id',type=None," \
                           f"default=1,default_factory={MISSING!r}," \
                           "init=True,repr=False,hash=None," \
                           "compare=True,metadata=mappingproxy({})," \
                           f"kw_only={MISSING!r}," \
                           "_field_type=None)"

        self.assertEqual(repr_output, expected_output)

    def test_field_recursive_repr(self):
        rec_field = field()
        rec_field.type = rec_field
        rec_field.name = "id"
        repr_output = repr(rec_field)

        self.assertIn(",type=...,", repr_output)

    def test_recursive_annotation(self):
        class C:
            pass

        @dataclass
        class D:
            C: C = field()

        self.assertIn(",type=...,", repr(D.__dataclass_fields__["C"]))

    def test_dataclass_params_repr(self):
        # Even though this is testing an internal implementation detail,
        # it's testing a feature we want to make sure is correctly implemented
        # for the sake of dataclasses itself
        @dataclass(slots=True, frozen=True)
        class Some: pass

        repr_output = repr(Some.__dataclass_params__)
        expected_output = "_DataclassParams(init=True,repr=True," \
                          "eq=True,order=False,unsafe_hash=False,frozen=True," \
                          "match_args=True,kw_only=False," \
                          "slots=True,weakref_slot=False)"
        self.assertEqual(repr_output, expected_output)

    def test_dataclass_params_signature(self):
        # Even though this is testing an internal implementation detail,
        # it's testing a feature we want to make sure is correctly implemented
        # for the sake of dataclasses itself
        @dataclass
        class Some: pass

        for param in inspect.signature(dataclass).parameters:
            if param == 'cls':
                continue
            self.assertTrue(hasattr(Some.__dataclass_params__, param), msg=param)

    def test_named_init_params(self):
        @dataclass
        class C:
            x: int

        o = C(x=32)
        self.assertEqual(o.x, 32)

    def test_two_fields_one_default(self):
        @dataclass
        class C:
            x: int
            y: int = 0

        o = C(3)
        self.assertEqual((o.x, o.y), (3, 0))

        # Non-defaults following defaults.
        with self.assertRaisesRegex(TypeError,
                                    "non-default argument 'y' follows "
                                    "default argument"):
            @dataclass
            class C:
                x: int = 0
                y: int

        # A derived class adds a non-default field after a default one.
        with self.assertRaisesRegex(TypeError,
                                    "non-default argument 'y' follows "
                                    "default argument"):
            @dataclass
            class B:
                x: int = 0

            @dataclass
            class C(B):
                y: int

        # Override a base class field and add a default to
        #  a field which didn't use to have a default.
        with self.assertRaisesRegex(TypeError,
                                    "non-default argument 'y' follows "
                                    "default argument"):
            @dataclass
            class B:
                x: int
                y: int

            @dataclass
            class C(B):
                x: int = 0

    def test_overwrite_hash(self):
        # Test that declaring this class isn't an error.  It should
        #  use the user-provided __hash__.
        @dataclass(frozen=True)
        class C:
            x: int
            def __hash__(self):
                return 301
        self.assertEqual(hash(C(100)), 301)

        # Test that declaring this class isn't an error.  It should
        #  use the generated __hash__.
        @dataclass(frozen=True)
        class C:
            x: int
            def __eq__(self, other):
                return False
        self.assertEqual(hash(C(100)), hash((100,)))

        # But this one should generate an exception, because with
        #  unsafe_hash=True, it's an error to have a __hash__ defined.
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __hash__'):
            @dataclass(unsafe_hash=True)
            class C:
                def __hash__(self):
                    pass

        # Creating this class should not generate an exception,
        #  because even though __hash__ exists before @dataclass is
        #  called, (due to __eq__ being defined), since it's None
        #  that's okay.
        @dataclass(unsafe_hash=True)
        class C:
            x: int
            def __eq__(self):
                pass
        # The generated hash function works as we'd expect.
        self.assertEqual(hash(C(10)), hash((10,)))

        # Creating this class should generate an exception, because
        #  __hash__ exists and is not None, which it would be if it
        #  had been auto-generated due to __eq__ being defined.
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __hash__'):
            @dataclass(unsafe_hash=True)
            class C:
                x: int
                def __eq__(self):
                    pass
                def __hash__(self):
                    pass

    def test_overwrite_fields_in_derived_class(self):
        # Note that x from C1 replaces x in Base, but the order remains
        #  the same as defined in Base.
        @dataclass
        class Base:
            x: Any = 15.0
            y: int = 0

        @dataclass
        class C1(Base):
            z: int = 10
            x: int = 15

        o = Base()
        self.assertEqual(repr(o), 'TestCase.test_overwrite_fields_in_derived_class.<locals>.Base(x=15.0, y=0)')

        o = C1()
        self.assertEqual(repr(o), 'TestCase.test_overwrite_fields_in_derived_class.<locals>.C1(x=15, y=0, z=10)')

        o = C1(x=5)
        self.assertEqual(repr(o), 'TestCase.test_overwrite_fields_in_derived_class.<locals>.C1(x=5, y=0, z=10)')

    def test_field_named_self(self):
        @dataclass
        class C:
            self: str
        c=C('foo')
        self.assertEqual(c.self, 'foo')

        # Make sure the first parameter is not named 'self'.
        sig = inspect.signature(C.__init__)
        first = next(iter(sig.parameters))
        self.assertNotEqual('self', first)

        # But we do use 'self' if no field named self.
        @dataclass
        class C:
            selfx: str

        # Make sure the first parameter is named 'self'.
        sig = inspect.signature(C.__init__)
        first = next(iter(sig.parameters))
        self.assertEqual('self', first)

    def test_field_named_object(self):
        @dataclass
        class C:
            object: str
        c = C('foo')
        self.assertEqual(c.object, 'foo')

    def test_field_named_object_frozen(self):
        @dataclass(frozen=True)
        class C:
            object: str
        c = C('foo')
        self.assertEqual(c.object, 'foo')

    def test_field_named_BUILTINS_frozen(self):
        # gh-96151
        @dataclass(frozen=True)
        class C:
            BUILTINS: int
        c = C(5)
        self.assertEqual(c.BUILTINS, 5)

    def test_field_with_special_single_underscore_names(self):
        # gh-98886

        @dataclass
        class X:
            x: int = field(default_factory=lambda: 111)
            _dflt_x: int = field(default_factory=lambda: 222)

        X()

        @dataclass
        class Y:
            y: int = field(default_factory=lambda: 111)
            _HAS_DEFAULT_FACTORY: int = 222

        assert Y(y=222).y == 222

    def test_field_named_like_builtin(self):
        # Attribute names can shadow built-in names
        # since code generation is used.
        # Ensure that this is not happening.
        exclusions = {'None', 'True', 'False'}
        builtins_names = sorted(
            b for b in builtins.__dict__.keys()
            if not b.startswith('__') and b not in exclusions
        )
        attributes = [(name, str) for name in builtins_names]
        C = make_dataclass('C', attributes)

        c = C(*[name for name in builtins_names])

        for name in builtins_names:
            self.assertEqual(getattr(c, name), name)

    def test_field_named_like_builtin_frozen(self):
        # Attribute names can shadow built-in names
        # since code generation is used.
        # Ensure that this is not happening
        # for frozen data classes.
        exclusions = {'None', 'True', 'False'}
        builtins_names = sorted(
            b for b in builtins.__dict__.keys()
            if not b.startswith('__') and b not in exclusions
        )
        attributes = [(name, str) for name in builtins_names]
        C = make_dataclass('C', attributes, frozen=True)

        c = C(*[name for name in builtins_names])

        for name in builtins_names:
            self.assertEqual(getattr(c, name), name)

    def test_0_field_compare(self):
        # Ensure that order=False is the default.
        @dataclass
        class C0:
            pass

        @dataclass(order=False)
        class C1:
            pass

        for cls in [C0, C1]:
            with self.subTest(cls=cls):
                self.assertEqual(cls(), cls())
                for idx, fn in enumerate([lambda a, b: a < b,
                                          lambda a, b: a <= b,
                                          lambda a, b: a > b,
                                          lambda a, b: a >= b]):
                    with self.subTest(idx=idx):
                        with self.assertRaisesRegex(TypeError,
                                                    f"not supported between instances of '{cls.__name__}' and '{cls.__name__}'"):
                            fn(cls(), cls())

        @dataclass(order=True)
        class C:
            pass
        self.assertLessEqual(C(), C())
        self.assertGreaterEqual(C(), C())

    def test_1_field_compare(self):
        # Ensure that order=False is the default.
        @dataclass
        class C0:
            x: int

        @dataclass(order=False)
        class C1:
            x: int

        for cls in [C0, C1]:
            with self.subTest(cls=cls):
                self.assertEqual(cls(1), cls(1))
                self.assertNotEqual(cls(0), cls(1))
                for idx, fn in enumerate([lambda a, b: a < b,
                                          lambda a, b: a <= b,
                                          lambda a, b: a > b,
                                          lambda a, b: a >= b]):
                    with self.subTest(idx=idx):
                        with self.assertRaisesRegex(TypeError,
                                                    f"not supported between instances of '{cls.__name__}' and '{cls.__name__}'"):
                            fn(cls(0), cls(0))

        @dataclass(order=True)
        class C:
            x: int
        self.assertLess(C(0), C(1))
        self.assertLessEqual(C(0), C(1))
        self.assertLessEqual(C(1), C(1))
        self.assertGreater(C(1), C(0))
        self.assertGreaterEqual(C(1), C(0))
        self.assertGreaterEqual(C(1), C(1))

    def test_simple_compare(self):
        # Ensure that order=False is the default.
        @dataclass
        class C0:
            x: int
            y: int

        @dataclass(order=False)
        class C1:
            x: int
            y: int

        for cls in [C0, C1]:
            with self.subTest(cls=cls):
                self.assertEqual(cls(0, 0), cls(0, 0))
                self.assertEqual(cls(1, 2), cls(1, 2))
                self.assertNotEqual(cls(1, 0), cls(0, 0))
                self.assertNotEqual(cls(1, 0), cls(1, 1))
                for idx, fn in enumerate([lambda a, b: a < b,
                                          lambda a, b: a <= b,
                                          lambda a, b: a > b,
                                          lambda a, b: a >= b]):
                    with self.subTest(idx=idx):
                        with self.assertRaisesRegex(TypeError,
                                                    f"not supported between instances of '{cls.__name__}' and '{cls.__name__}'"):
                            fn(cls(0, 0), cls(0, 0))

        @dataclass(order=True)
        class C:
            x: int
            y: int

        for idx, fn in enumerate([lambda a, b: a == b,
                                  lambda a, b: a <= b,
                                  lambda a, b: a >= b]):
            with self.subTest(idx=idx):
                self.assertTrue(fn(C(0, 0), C(0, 0)))

        for idx, fn in enumerate([lambda a, b: a < b,
                                  lambda a, b: a <= b,
                                  lambda a, b: a != b]):
            with self.subTest(idx=idx):
                self.assertTrue(fn(C(0, 0), C(0, 1)))
                self.assertTrue(fn(C(0, 1), C(1, 0)))
                self.assertTrue(fn(C(1, 0), C(1, 1)))

        for idx, fn in enumerate([lambda a, b: a > b,
                                  lambda a, b: a >= b,
                                  lambda a, b: a != b]):
            with self.subTest(idx=idx):
                self.assertTrue(fn(C(0, 1), C(0, 0)))
                self.assertTrue(fn(C(1, 0), C(0, 1)))
                self.assertTrue(fn(C(1, 1), C(1, 0)))

    def test_compare_subclasses(self):
        # Comparisons fail for subclasses, even if no fields
        #  are added.
        @dataclass
        class B:
            i: int

        @dataclass
        class C(B):
            pass

        for idx, (fn, expected) in enumerate([(lambda a, b: a == b, False),
                                              (lambda a, b: a != b, True)]):
            with self.subTest(idx=idx):
                self.assertEqual(fn(B(0), C(0)), expected)

        for idx, fn in enumerate([lambda a, b: a < b,
                                  lambda a, b: a <= b,
                                  lambda a, b: a > b,
                                  lambda a, b: a >= b]):
            with self.subTest(idx=idx):
                with self.assertRaisesRegex(TypeError,
                                            "not supported between instances of 'B' and 'C'"):
                    fn(B(0), C(0))

    def test_eq_order(self):
        # Test combining eq and order.
        for (eq,    order, result   ) in [
            (False, False, 'neither'),
            (False, True,  'exception'),
            (True,  False, 'eq_only'),
            (True,  True,  'both'),
        ]:
            with self.subTest(eq=eq, order=order):
                if result == 'exception':
                    with self.assertRaisesRegex(ValueError, 'eq must be true if order is true'):
                        @dataclass(eq=eq, order=order)
                        class C:
                            pass
                else:
                    @dataclass(eq=eq, order=order)
                    class C:
                        pass

                    if result == 'neither':
                        self.assertNotIn('__eq__', C.__dict__)
                        self.assertNotIn('__lt__', C.__dict__)
                        self.assertNotIn('__le__', C.__dict__)
                        self.assertNotIn('__gt__', C.__dict__)
                        self.assertNotIn('__ge__', C.__dict__)
                    elif result == 'both':
                        self.assertIn('__eq__', C.__dict__)
                        self.assertIn('__lt__', C.__dict__)
                        self.assertIn('__le__', C.__dict__)
                        self.assertIn('__gt__', C.__dict__)
                        self.assertIn('__ge__', C.__dict__)
                    elif result == 'eq_only':
                        self.assertIn('__eq__', C.__dict__)
                        self.assertNotIn('__lt__', C.__dict__)
                        self.assertNotIn('__le__', C.__dict__)
                        self.assertNotIn('__gt__', C.__dict__)
                        self.assertNotIn('__ge__', C.__dict__)
                    else:
                        assert False, f'unknown result {result!r}'

    def test_field_no_default(self):
        @dataclass
        class C:
            x: int = field()

        self.assertEqual(C(5).x, 5)

        with self.assertRaisesRegex(TypeError,
                                    r"__init__\(\) missing 1 required "
                                    "positional argument: 'x'"):
            C()

    def test_field_default(self):
        default = object()
        @dataclass
        class C:
            x: object = field(default=default)

        self.assertIs(C.x, default)
        c = C(10)
        self.assertEqual(c.x, 10)

        # If we delete the instance attribute, we should then see the
        #  class attribute.
        del c.x
        self.assertIs(c.x, default)

        self.assertIs(C().x, default)

    def test_not_in_repr(self):
        @dataclass
        class C:
            x: int = field(repr=False)
        with self.assertRaises(TypeError):
            C()
        c = C(10)
        self.assertEqual(repr(c), 'TestCase.test_not_in_repr.<locals>.C()')

        @dataclass
        class C:
            x: int = field(repr=False)
            y: int
        c = C(10, 20)
        self.assertEqual(repr(c), 'TestCase.test_not_in_repr.<locals>.C(y=20)')

    def test_not_in_compare(self):
        @dataclass
        class C:
            x: int = 0
            y: int = field(compare=False, default=4)

        self.assertEqual(C(), C(0, 20))
        self.assertEqual(C(1, 10), C(1, 20))
        self.assertNotEqual(C(3), C(4, 10))
        self.assertNotEqual(C(3, 10), C(4, 10))

    def test_no_unhashable_default(self):
        # See bpo-44674.
        class Unhashable:
            __hash__ = None

        unhashable_re = 'mutable default .* for field a is not allowed'
        with self.assertRaisesRegex(ValueError, unhashable_re):
            @dataclass
            class A:
                a: dict = {}

        with self.assertRaisesRegex(ValueError, unhashable_re):
            @dataclass
            class A:
                a: Any = Unhashable()

        # Make sure that the machinery looking for hashability is using the
        # class's __hash__, not the instance's __hash__.
        with self.assertRaisesRegex(ValueError, unhashable_re):
            unhashable = Unhashable()
            # This shouldn't make the variable hashable.
            unhashable.__hash__ = lambda: 0
            @dataclass
            class A:
                a: Any = unhashable

    def test_hash_field_rules(self):
        # Test all 6 cases of:
        #  hash=True/False/None
        #  compare=True/False
        for (hash_,    compare, result  ) in [
            (True,     False,   'field' ),
            (True,     True,    'field' ),
            (False,    False,   'absent'),
            (False,    True,    'absent'),
            (None,     False,   'absent'),
            (None,     True,    'field' ),
            ]:
            with self.subTest(hash=hash_, compare=compare):
                @dataclass(unsafe_hash=True)
                class C:
                    x: int = field(compare=compare, hash=hash_, default=5)

                if result == 'field':
                    # __hash__ contains the field.
                    self.assertEqual(hash(C(5)), hash((5,)))
                elif result == 'absent':
                    # The field is not present in the hash.
                    self.assertEqual(hash(C(5)), hash(()))
                else:
                    assert False, f'unknown result {result!r}'

    def test_init_false_no_default(self):
        # If init=False and no default value, then the field won't be
        #  present in the instance.
        @dataclass
        class C:
            x: int = field(init=False)

        self.assertNotIn('x', C().__dict__)

        @dataclass
        class C:
            x: int
            y: int = 0
            z: int = field(init=False)
            t: int = 10

        self.assertNotIn('z', C(0).__dict__)
        self.assertEqual(vars(C(5)), {'t': 10, 'x': 5, 'y': 0})

    def test_class_marker(self):
        @dataclass
        class C:
            x: int
            y: str = field(init=False, default=None)
            z: str = field(repr=False)

        the_fields = fields(C)
        # the_fields is a tuple of 3 items, each value
        #  is in __annotations__.
        self.assertIsInstance(the_fields, tuple)
        for f in the_fields:
            self.assertIs(type(f), Field)
            self.assertIn(f.name, C.__annotations__)

        self.assertEqual(len(the_fields), 3)

        self.assertEqual(the_fields[0].name, 'x')
        self.assertEqual(the_fields[0].type, int)
        self.assertFalse(hasattr(C, 'x'))
        self.assertTrue (the_fields[0].init)
        self.assertTrue (the_fields[0].repr)
        self.assertEqual(the_fields[1].name, 'y')
        self.assertEqual(the_fields[1].type, str)
        self.assertIsNone(getattr(C, 'y'))
        self.assertFalse(the_fields[1].init)
        self.assertTrue (the_fields[1].repr)
        self.assertEqual(the_fields[2].name, 'z')
        self.assertEqual(the_fields[2].type, str)
        self.assertFalse(hasattr(C, 'z'))
        self.assertTrue (the_fields[2].init)
        self.assertFalse(the_fields[2].repr)

    def test_field_order(self):
        @dataclass
        class B:
            a: str = 'B:a'
            b: str = 'B:b'
            c: str = 'B:c'

        @dataclass
        class C(B):
            b: str = 'C:b'

        self.assertEqual([(f.name, f.default) for f in fields(C)],
                         [('a', 'B:a'),
                          ('b', 'C:b'),
                          ('c', 'B:c')])

        @dataclass
        class D(B):
            c: str = 'D:c'

        self.assertEqual([(f.name, f.default) for f in fields(D)],
                         [('a', 'B:a'),
                          ('b', 'B:b'),
                          ('c', 'D:c')])

        @dataclass
        class E(D):
            a: str = 'E:a'
            d: str = 'E:d'

        self.assertEqual([(f.name, f.default) for f in fields(E)],
                         [('a', 'E:a'),
                          ('b', 'B:b'),
                          ('c', 'D:c'),
                          ('d', 'E:d')])

    def test_class_attrs(self):
        # We only have a class attribute if a default value is
        #  specified, either directly or via a field with a default.
        default = object()
        @dataclass
        class C:
            x: int
            y: int = field(repr=False)
            z: object = default
            t: int = field(default=100)

        self.assertFalse(hasattr(C, 'x'))
        self.assertFalse(hasattr(C, 'y'))
        self.assertIs   (C.z, default)
        self.assertEqual(C.t, 100)

    def test_disallowed_mutable_defaults(self):
        # For the known types, don't allow mutable default values.
        for typ, empty, non_empty in [(list, [], [1]),
                                      (dict, {}, {0:1}),
                                      (set, set(), set([1])),
                                      ]:
            with self.subTest(typ=typ):
                # Can't use a zero-length value.
                with self.assertRaisesRegex(ValueError,
                                            f'mutable default {typ} for field '
                                            'x is not allowed'):
                    @dataclass
                    class Point:
                        x: typ = empty


                # Nor a non-zero-length value
                with self.assertRaisesRegex(ValueError,
                                            f'mutable default {typ} for field '
                                            'y is not allowed'):
                    @dataclass
                    class Point:
                        y: typ = non_empty

                # Check subtypes also fail.
                class Subclass(typ): pass

                with self.assertRaisesRegex(ValueError,
                                            "mutable default .*Subclass'>"
                                            " for field z is not allowed"
                                            ):
                    @dataclass
                    class Point:
                        z: typ = Subclass()

                # Because this is a ClassVar, it can be mutable.
                @dataclass
                class C:
                    z: ClassVar[typ] = typ()

                # Because this is a ClassVar, it can be mutable.
                @dataclass
                class C:
                    x: ClassVar[typ] = Subclass()

    def test_deliberately_mutable_defaults(self):
        # If a mutable default isn't in the known list of
        #  (list, dict, set), then it's okay.
        class Mutable:
            def __init__(self):
                self.l = []

        @dataclass
        class C:
            x: Mutable

        # These 2 instances will share this value of x.
        lst = Mutable()
        o1 = C(lst)
        o2 = C(lst)
        self.assertEqual(o1, o2)
        o1.x.l.extend([1, 2])
        self.assertEqual(o1, o2)
        self.assertEqual(o1.x.l, [1, 2])
        self.assertIs(o1.x, o2.x)

    def test_no_options(self):
        # Call with dataclass().
        @dataclass()
        class C:
            x: int

        self.assertEqual(C(42).x, 42)

    def test_not_tuple(self):
        # Make sure we can't be compared to a tuple.
        @dataclass
        class Point:
            x: int
            y: int
        self.assertNotEqual(Point(1, 2), (1, 2))

        # And that we can't compare to another unrelated dataclass.
        @dataclass
        class C:
            x: int
            y: int
        self.assertNotEqual(Point(1, 3), C(1, 3))

    def test_not_other_dataclass(self):
        # Test that some of the problems with namedtuple don't happen
        #  here.
        @dataclass
        class Point3D:
            x: int
            y: int
            z: int

        @dataclass
        class Date:
            year: int
            month: int
            day: int

        self.assertNotEqual(Point3D(2017, 6, 3), Date(2017, 6, 3))
        self.assertNotEqual(Point3D(1, 2, 3), (1, 2, 3))

        # Make sure we can't unpack.
        with self.assertRaisesRegex(TypeError, 'unpack'):
            x, y, z = Point3D(4, 5, 6)

        # Make sure another class with the same field names isn't
        #  equal.
        @dataclass
        class Point3Dv1:
            x: int = 0
            y: int = 0
            z: int = 0
        self.assertNotEqual(Point3D(0, 0, 0), Point3Dv1())

    def test_function_annotations(self):
        # Some dummy class and instance to use as a default.
        class F:
            pass
        f = F()

        def validate_class(cls):
            # First, check __annotations__, even though they're not
            #  function annotations.
            self.assertEqual(cls.__annotations__['i'], int)
            self.assertEqual(cls.__annotations__['j'], str)
            self.assertEqual(cls.__annotations__['k'], F)
            self.assertEqual(cls.__annotations__['l'], float)
            self.assertEqual(cls.__annotations__['z'], complex)

            # Verify __init__.

            signature = inspect.signature(cls.__init__)
            # Check the return type, should be None.
            self.assertIs(signature.return_annotation, None)

            # Check each parameter.
            params = iter(signature.parameters.values())
            param = next(params)
            # This is testing an internal name, and probably shouldn't be tested.
            self.assertEqual(param.name, 'self')
            param = next(params)
            self.assertEqual(param.name, 'i')
            self.assertIs   (param.annotation, int)
            self.assertEqual(param.default, inspect.Parameter.empty)
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            param = next(params)
            self.assertEqual(param.name, 'j')
            self.assertIs   (param.annotation, str)
            self.assertEqual(param.default, inspect.Parameter.empty)
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            param = next(params)
            self.assertEqual(param.name, 'k')
            self.assertIs   (param.annotation, F)
            # Don't test for the default, since it's set to MISSING.
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            param = next(params)
            self.assertEqual(param.name, 'l')
            self.assertIs   (param.annotation, float)
            # Don't test for the default, since it's set to MISSING.
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            self.assertRaises(StopIteration, next, params)


        @dataclass
        class C:
            i: int
            j: str
            k: F = f
            l: float=field(default=None)
            z: complex=field(default=3+4j, init=False)

        validate_class(C)

        # Now repeat with __hash__.
        @dataclass(frozen=True, unsafe_hash=True)
        class C:
            i: int
            j: str
            k: F = f
            l: float=field(default=None)
            z: complex=field(default=3+4j, init=False)

        validate_class(C)

    def test_missing_default(self):
        # Test that MISSING works the same as a default not being
        #  specified.
        @dataclass
        class C:
            x: int=field(default=MISSING)
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            C()
        self.assertNotIn('x', C.__dict__)

        @dataclass
        class D:
            x: int
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            D()
        self.assertNotIn('x', D.__dict__)

    def test_missing_default_factory(self):
        # Test that MISSING works the same as a default factory not
        #  being specified (which is really the same as a default not
        #  being specified, too).
        @dataclass
        class C:
            x: int=field(default_factory=MISSING)
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            C()
        self.assertNotIn('x', C.__dict__)

        @dataclass
        class D:
            x: int=field(default=MISSING, default_factory=MISSING)
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            D()
        self.assertNotIn('x', D.__dict__)

    def test_missing_repr(self):
        self.assertIn('MISSING_TYPE object', repr(MISSING))

    def test_dont_include_other_annotations(self):
        @dataclass
        class C:
            i: int
            def foo(self) -> int:
                return 4
            @property
            def bar(self) -> int:
                return 5
        self.assertEqual(list(C.__annotations__), ['i'])
        self.assertEqual(C(10).foo(), 4)
        self.assertEqual(C(10).bar, 5)
        self.assertEqual(C(10).i, 10)

    def test_post_init(self):
        # Just make sure it gets called
        @dataclass
        class C:
            def __post_init__(self):
                raise CustomError()
        with self.assertRaises(CustomError):
            C()

        @dataclass
        class C:
            i: int = 10
            def __post_init__(self):
                if self.i == 10:
                    raise CustomError()
        with self.assertRaises(CustomError):
            C()
        # post-init gets called, but doesn't raise. This is just
        #  checking that self is used correctly.
        C(5)

        # If there's not an __init__, then post-init won't get called.
        @dataclass(init=False)
        class C:
            def __post_init__(self):
                raise CustomError()
        # Creating the class won't raise
        C()

        @dataclass
        class C:
            x: int = 0
            def __post_init__(self):
                self.x *= 2
        self.assertEqual(C().x, 0)
        self.assertEqual(C(2).x, 4)

        # Make sure that if we're frozen, post-init can't set
        #  attributes.
        @dataclass(frozen=True)
        class C:
            x: int = 0
            def __post_init__(self):
                self.x *= 2
        with self.assertRaises(FrozenInstanceError):
            C()

    def test_post_init_super(self):
        # Make sure super() post-init isn't called by default.
        class B:
            def __post_init__(self):
                raise CustomError()

        @dataclass
        class C(B):
            def __post_init__(self):
                self.x = 5

        self.assertEqual(C().x, 5)

        # Now call super(), and it will raise.
        @dataclass
        class C(B):
            def __post_init__(self):
                super().__post_init__()

        with self.assertRaises(CustomError):
            C()

        # Make sure post-init is called, even if not defined in our
        #  class.
        @dataclass
        class C(B):
            pass

        with self.assertRaises(CustomError):
            C()

    def test_post_init_staticmethod(self):
        flag = False
        @dataclass
        class C:
            x: int
            y: int
            @staticmethod
            def __post_init__():
                nonlocal flag
                flag = True

        self.assertFalse(flag)
        c = C(3, 4)
        self.assertEqual((c.x, c.y), (3, 4))
        self.assertTrue(flag)

    def test_post_init_classmethod(self):
        @dataclass
        class C:
            flag = False
            x: int
            y: int
            @classmethod
            def __post_init__(cls):
                cls.flag = True

        self.assertFalse(C.flag)
        c = C(3, 4)
        self.assertEqual((c.x, c.y), (3, 4))
        self.assertTrue(C.flag)

    def test_post_init_not_auto_added(self):
        # See bpo-46757, which had proposed always adding __post_init__.  As
        # Raymond Hettinger pointed out, that would be a breaking change.  So,
        # add a test to make sure that the current behavior doesn't change.

        @dataclass
        class A0:
            pass

        @dataclass
        class B0:
            b_called: bool = False
            def __post_init__(self):
                self.b_called = True

        @dataclass
        class C0(A0, B0):
            c_called: bool = False
            def __post_init__(self):
                super().__post_init__()
                self.c_called = True

        # Since A0 has no __post_init__, and one wasn't automatically added
        # (because that's the rule: it's never added by @dataclass, it's only
        # the class author that can add it), then B0.__post_init__ is called.
        # Verify that.
        c = C0()
        self.assertTrue(c.b_called)
        self.assertTrue(c.c_called)

        ######################################
        # Now, the same thing, except A1 defines __post_init__.
        @dataclass
        class A1:
            def __post_init__(self):
                pass

        @dataclass
        class B1:
            b_called: bool = False
            def __post_init__(self):
                self.b_called = True

        @dataclass
        class C1(A1, B1):
            c_called: bool = False
            def __post_init__(self):
                super().__post_init__()
                self.c_called = True

        # This time, B1.__post_init__ isn't being called.  This mimics what
        # would happen if A1.__post_init__ had been automatically added,
        # instead of manually added as we see here.  This test isn't really
        # needed, but I'm including it just to demonstrate the changed
        # behavior when A1 does define __post_init__.
        c = C1()
        self.assertFalse(c.b_called)
        self.assertTrue(c.c_called)

    def test_class_var(self):
        # Make sure ClassVars are ignored in __init__, __repr__, etc.
        @dataclass
        class C:
            x: int
            y: int = 10
            z: ClassVar[int] = 1000
            w: ClassVar[int] = 2000
            t: ClassVar[int] = 3000
            s: ClassVar      = 4000

        c = C(5)
        self.assertEqual(repr(c), 'TestCase.test_class_var.<locals>.C(x=5, y=10)')
        self.assertEqual(len(fields(C)), 2)                 # We have 2 fields.
        self.assertEqual(len(C.__annotations__), 6)         # And 4 ClassVars.
        self.assertEqual(c.z, 1000)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)
        self.assertEqual(c.s, 4000)
        C.z += 1
        self.assertEqual(c.z, 1001)
        c = C(20)
        self.assertEqual((c.x, c.y), (20, 10))
        self.assertEqual(c.z, 1001)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)
        self.assertEqual(c.s, 4000)

    def test_class_var_no_default(self):
        # If a ClassVar has no default value, it should not be set on the class.
        @dataclass
        class C:
            x: ClassVar[int]

        self.assertNotIn('x', C.__dict__)

    def test_class_var_default_factory(self):
        # It makes no sense for a ClassVar to have a default factory. When
        #  would it be called? Call it yourself, since it's class-wide.
        with self.assertRaisesRegex(TypeError,
                                    'cannot have a default factory'):
            @dataclass
            class C:
                x: ClassVar[int] = field(default_factory=int)

            self.assertNotIn('x', C.__dict__)

    def test_class_var_with_default(self):
        # If a ClassVar has a default value, it should be set on the class.
        @dataclass
        class C:
            x: ClassVar[int] = 10
        self.assertEqual(C.x, 10)

        @dataclass
        class C:
            x: ClassVar[int] = field(default=10)
        self.assertEqual(C.x, 10)

    def test_class_var_frozen(self):
        # Make sure ClassVars work even if we're frozen.
        @dataclass(frozen=True)
        class C:
            x: int
            y: int = 10
            z: ClassVar[int] = 1000
            w: ClassVar[int] = 2000
            t: ClassVar[int] = 3000

        c = C(5)
        self.assertEqual(repr(C(5)), 'TestCase.test_class_var_frozen.<locals>.C(x=5, y=10)')
        self.assertEqual(len(fields(C)), 2)                 # We have 2 fields
        self.assertEqual(len(C.__annotations__), 5)         # And 3 ClassVars
        self.assertEqual(c.z, 1000)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)
        # We can still modify the ClassVar, it's only instances that are
        #  frozen.
        C.z += 1
        self.assertEqual(c.z, 1001)
        c = C(20)
        self.assertEqual((c.x, c.y), (20, 10))
        self.assertEqual(c.z, 1001)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)

    def test_init_var_no_default(self):
        # If an InitVar has no default value, it should not be set on the class.
        @dataclass
        class C:
            x: InitVar[int]

        self.assertNotIn('x', C.__dict__)

    def test_init_var_default_factory(self):
        # It makes no sense for an InitVar to have a default factory. When
        #  would it be called? Call it yourself, since it's class-wide.
        with self.assertRaisesRegex(TypeError,
                                    'cannot have a default factory'):
            @dataclass
            class C:
                x: InitVar[int] = field(default_factory=int)

            self.assertNotIn('x', C.__dict__)

    def test_init_var_with_default(self):
        # If an InitVar has a default value, it should be set on the class.
        @dataclass
        class C:
            x: InitVar[int] = 10
        self.assertEqual(C.x, 10)

        @dataclass
        class C:
            x: InitVar[int] = field(default=10)
        self.assertEqual(C.x, 10)

    def test_init_var(self):
        @dataclass
        class C:
            x: int = None
            init_param: InitVar[int] = None

            def __post_init__(self, init_param):
                if self.x is None:
                    self.x = init_param*2

        c = C(init_param=10)
        self.assertEqual(c.x, 20)

    def test_init_var_preserve_type(self):
        self.assertEqual(InitVar[int].type, int)

        # Make sure the repr is correct.
        self.assertEqual(repr(InitVar[int]), 'dataclasses.InitVar[int]')
        self.assertEqual(repr(InitVar[List[int]]),
                         'dataclasses.InitVar[typing.List[int]]')
        self.assertEqual(repr(InitVar[list[int]]),
                         'dataclasses.InitVar[list[int]]')
        self.assertEqual(repr(InitVar[int|str]),
                         'dataclasses.InitVar[int | str]')

    def test_init_var_inheritance(self):
        # Note that this deliberately tests that a dataclass need not
        #  have a __post_init__ function if it has an InitVar field.
        #  It could just be used in a derived class, as shown here.
        @dataclass
        class Base:
            x: int
            init_base: InitVar[int]

        # We can instantiate by passing the InitVar, even though
        #  it's not used.
        b = Base(0, 10)
        self.assertEqual(vars(b), {'x': 0})

        @dataclass
        class C(Base):
            y: int
            init_derived: InitVar[int]

            def __post_init__(self, init_base, init_derived):
                self.x = self.x + init_base
                self.y = self.y + init_derived

        c = C(10, 11, 50, 51)
        self.assertEqual(vars(c), {'x': 21, 'y': 101})

    def test_default_factory(self):
        # Test a factory that returns a new list.
        @dataclass
        class C:
            x: int
            y: list = field(default_factory=list)

        c0 = C(3)
        c1 = C(3)
        self.assertEqual(c0.x, 3)
        self.assertEqual(c0.y, [])
        self.assertEqual(c0, c1)
        self.assertIsNot(c0.y, c1.y)
        self.assertEqual(astuple(C(5, [1])), (5, [1]))

        # Test a factory that returns a shared list.
        l = []
        @dataclass
        class C:
            x: int
            y: list = field(default_factory=lambda: l)

        c0 = C(3)
        c1 = C(3)
        self.assertEqual(c0.x, 3)
        self.assertEqual(c0.y, [])
        self.assertEqual(c0, c1)
        self.assertIs(c0.y, c1.y)
        self.assertEqual(astuple(C(5, [1])), (5, [1]))

        # Test various other field flags.
        # repr
        @dataclass
        class C:
            x: list = field(default_factory=list, repr=False)
        self.assertEqual(repr(C()), 'TestCase.test_default_factory.<locals>.C()')
        self.assertEqual(C().x, [])

        # hash
        @dataclass(unsafe_hash=True)
        class C:
            x: list = field(default_factory=list, hash=False)
        self.assertEqual(astuple(C()), ([],))
        self.assertEqual(hash(C()), hash(()))

        # init (see also test_default_factory_with_no_init)
        @dataclass
        class C:
            x: list = field(default_factory=list, init=False)
        self.assertEqual(astuple(C()), ([],))

        # compare
        @dataclass
        class C:
            x: list = field(default_factory=list, compare=False)
        self.assertEqual(C(), C([1]))

    def test_default_factory_with_no_init(self):
        # We need a factory with a side effect.
        factory = Mock()

        @dataclass
        class C:
            x: list = field(default_factory=factory, init=False)

        # Make sure the default factory is called for each new instance.
        C().x
        self.assertEqual(factory.call_count, 1)
        C().x
        self.assertEqual(factory.call_count, 2)

    def test_default_factory_not_called_if_value_given(self):
        # We need a factory that we can test if it's been called.
        factory = Mock()

        @dataclass
        class C:
            x: int = field(default_factory=factory)

        # Make sure that if a field has a default factory function,
        #  it's not called if a value is specified.
        C().x
        self.assertEqual(factory.call_count, 1)
        self.assertEqual(C(10).x, 10)
        self.assertEqual(factory.call_count, 1)
        C().x
        self.assertEqual(factory.call_count, 2)

    def test_default_factory_derived(self):
        # See bpo-32896.
        @dataclass
        class Foo:
            x: dict = field(default_factory=dict)

        @dataclass
        class Bar(Foo):
            y: int = 1

        self.assertEqual(Foo().x, {})
        self.assertEqual(Bar().x, {})
        self.assertEqual(Bar().y, 1)

        @dataclass
        class Baz(Foo):
            pass
        self.assertEqual(Baz().x, {})

    def test_intermediate_non_dataclass(self):
        # Test that an intermediate class that defines
        #  annotations does not define fields.

        @dataclass
        class A:
            x: int

        class B(A):
            y: int

        @dataclass
        class C(B):
            z: int

        c = C(1, 3)
        self.assertEqual((c.x, c.z), (1, 3))

        # .y was not initialized.
        with self.assertRaisesRegex(AttributeError,
                                    'object has no attribute'):
            c.y

        # And if we again derive a non-dataclass, no fields are added.
        class D(C):
            t: int
        d = D(4, 5)
        self.assertEqual((d.x, d.z), (4, 5))

    def test_classvar_default_factory(self):
        # It's an error for a ClassVar to have a factory function.
        with self.assertRaisesRegex(TypeError,
                                    'cannot have a default factory'):
            @dataclass
            class C:
                x: ClassVar[int] = field(default_factory=int)

    def test_is_dataclass(self):
        class NotDataClass:
            pass

        self.assertFalse(is_dataclass(0))
        self.assertFalse(is_dataclass(int))
        self.assertFalse(is_dataclass(NotDataClass))
        self.assertFalse(is_dataclass(NotDataClass()))

        @dataclass
        class C:
            x: int

        @dataclass
        class D:
            d: C
            e: int

        c = C(10)
        d = D(c, 4)

        self.assertTrue(is_dataclass(C))
        self.assertTrue(is_dataclass(c))
        self.assertFalse(is_dataclass(c.x))
        self.assertTrue(is_dataclass(d.d))
        self.assertFalse(is_dataclass(d.e))

    def test_is_dataclass_when_getattr_always_returns(self):
        # See bpo-37868.
        class A:
            def __getattr__(self, key):
                return 0
        self.assertFalse(is_dataclass(A))
        a = A()

        # Also test for an instance attribute.
        class B:
            pass
        b = B()
        b.__dataclass_fields__ = []

        for obj in a, b:
            with self.subTest(obj=obj):
                self.assertFalse(is_dataclass(obj))

                # Indirect tests for _is_dataclass_instance().
                with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'):
                    asdict(obj)
                with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'):
                    astuple(obj)
                with self.assertRaisesRegex(TypeError, 'should be called on dataclass instances'):
                    replace(obj, x=0)

    def test_is_dataclass_genericalias(self):
        @dataclass
        class A(types.GenericAlias):
            origin: type
            args: type
        self.assertTrue(is_dataclass(A))
        a = A(list, int)
        self.assertTrue(is_dataclass(type(a)))
        self.assertTrue(is_dataclass(a))


    def test_helper_fields_with_class_instance(self):
        # Check that we can call fields() on either a class or instance,
        #  and get back the same thing.
        @dataclass
        class C:
            x: int
            y: float

        self.assertEqual(fields(C), fields(C(0, 0.0)))

    def test_helper_fields_exception(self):
        # Check that TypeError is raised if not passed a dataclass or
        #  instance.
        with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
            fields(0)

        class C: pass
        with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
            fields(C)
        with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
            fields(C())

    def test_clean_traceback_from_fields_exception(self):
        stdout = io.StringIO()
        try:
            fields(object)
        except TypeError as exc:
            traceback.print_exception(exc, file=stdout)
        printed_traceback = stdout.getvalue()
        self.assertNotIn("AttributeError", printed_traceback)
        self.assertNotIn("__dataclass_fields__", printed_traceback)

    def test_helper_asdict(self):
        # Basic tests for asdict(), it should return a new dictionary.
        @dataclass
        class C:
            x: int
            y: int
        c = C(1, 2)

        self.assertEqual(asdict(c), {'x': 1, 'y': 2})
        self.assertEqual(asdict(c), asdict(c))
        self.assertIsNot(asdict(c), asdict(c))
        c.x = 42
        self.assertEqual(asdict(c), {'x': 42, 'y': 2})
        self.assertIs(type(asdict(c)), dict)

    def test_helper_asdict_raises_on_classes(self):
        # asdict() should raise on a class object.
        @dataclass
        class C:
            x: int
            y: int
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            asdict(C)
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            asdict(int)

    def test_helper_asdict_copy_values(self):
        @dataclass
        class C:
            x: int
            y: List[int] = field(default_factory=list)
        initial = []
        c = C(1, initial)
        d = asdict(c)
        self.assertEqual(d['y'], initial)
        self.assertIsNot(d['y'], initial)
        c = C(1)
        d = asdict(c)
        d['y'].append(1)
        self.assertEqual(c.y, [])

    def test_helper_asdict_nested(self):
        @dataclass
        class UserId:
            token: int
            group: int
        @dataclass
        class User:
            name: str
            id: UserId
        u = User('Joe', UserId(123, 1))
        d = asdict(u)
        self.assertEqual(d, {'name': 'Joe', 'id': {'token': 123, 'group': 1}})
        self.assertIsNot(asdict(u), asdict(u))
        u.id.group = 2
        self.assertEqual(asdict(u), {'name': 'Joe',
                                     'id': {'token': 123, 'group': 2}})

    def test_helper_asdict_builtin_containers(self):
        @dataclass
        class User:
            name: str
            id: int
        @dataclass
        class GroupList:
            id: int
            users: List[User]
        @dataclass
        class GroupTuple:
            id: int
            users: Tuple[User, ...]
        @dataclass
        class GroupDict:
            id: int
            users: Dict[str, User]
        a = User('Alice', 1)
        b = User('Bob', 2)
        gl = GroupList(0, [a, b])
        gt = GroupTuple(0, (a, b))
        gd = GroupDict(0, {'first': a, 'second': b})
        self.assertEqual(asdict(gl), {'id': 0, 'users': [{'name': 'Alice', 'id': 1},
                                                         {'name': 'Bob', 'id': 2}]})
        self.assertEqual(asdict(gt), {'id': 0, 'users': ({'name': 'Alice', 'id': 1},
                                                         {'name': 'Bob', 'id': 2})})
        self.assertEqual(asdict(gd), {'id': 0, 'users': {'first': {'name': 'Alice', 'id': 1},
                                                         'second': {'name': 'Bob', 'id': 2}}})

    def test_helper_asdict_builtin_object_containers(self):
        @dataclass
        class Child:
            d: object

        @dataclass
        class Parent:
            child: Child

        self.assertEqual(asdict(Parent(Child([1]))), {'child': {'d': [1]}})
        self.assertEqual(asdict(Parent(Child({1: 2}))), {'child': {'d': {1: 2}}})

    def test_helper_asdict_factory(self):
        @dataclass
        class C:
            x: int
            y: int
        c = C(1, 2)
        d = asdict(c, dict_factory=OrderedDict)
        self.assertEqual(d, OrderedDict([('x', 1), ('y', 2)]))
        self.assertIsNot(d, asdict(c, dict_factory=OrderedDict))
        c.x = 42
        d = asdict(c, dict_factory=OrderedDict)
        self.assertEqual(d, OrderedDict([('x', 42), ('y', 2)]))
        self.assertIs(type(d), OrderedDict)

    def test_helper_asdict_namedtuple(self):
        T = namedtuple('T', 'a b c')
        @dataclass
        class C:
            x: str
            y: T
        c = C('outer', T(1, C('inner', T(11, 12, 13)), 2))

        d = asdict(c)
        self.assertEqual(d, {'x': 'outer',
                             'y': T(1,
                                    {'x': 'inner',
                                     'y': T(11, 12, 13)},
                                    2),
                             }
                         )

        # Now with a dict_factory.  OrderedDict is convenient, but
        # since it compares to dicts, we also need to have separate
        # assertIs tests.
        d = asdict(c, dict_factory=OrderedDict)
        self.assertEqual(d, {'x': 'outer',
                             'y': T(1,
                                    {'x': 'inner',
                                     'y': T(11, 12, 13)},
                                    2),
                             }
                         )

        # Make sure that the returned dicts are actually OrderedDicts.
        self.assertIs(type(d), OrderedDict)
        self.assertIs(type(d['y'][1]), OrderedDict)

    def test_helper_asdict_namedtuple_key(self):
        # Ensure that a field that contains a dict which has a
        # namedtuple as a key works with asdict().

        @dataclass
        class C:
            f: dict
        T = namedtuple('T', 'a')

        c = C({T('an a'): 0})

        self.assertEqual(asdict(c), {'f': {T(a='an a'): 0}})

    def test_helper_asdict_namedtuple_derived(self):
        class T(namedtuple('Tbase', 'a')):
            def my_a(self):
                return self.a

        @dataclass
        class C:
            f: T

        t = T(6)
        c = C(t)

        d = asdict(c)
        self.assertEqual(d, {'f': T(a=6)})
        # Make sure that t has been copied, not used directly.
        self.assertIsNot(d['f'], t)
        self.assertEqual(d['f'].my_a(), 6)

    def test_helper_asdict_defaultdict(self):
        # Ensure asdict() does not throw exceptions when a
        # defaultdict is a member of a dataclass
        @dataclass
        class C:
            mp: DefaultDict[str, List]

        dd = defaultdict(list)
        dd["x"].append(12)
        c = C(mp=dd)
        d = asdict(c)

        self.assertEqual(d, {"mp": {"x": [12]}})
        self.assertTrue(d["mp"] is not c.mp)  # make sure defaultdict is copied

    def test_helper_astuple(self):
        # Basic tests for astuple(), it should return a new tuple.
        @dataclass
        class C:
            x: int
            y: int = 0
        c = C(1)

        self.assertEqual(astuple(c), (1, 0))
        self.assertEqual(astuple(c), astuple(c))
        self.assertIsNot(astuple(c), astuple(c))
        c.y = 42
        self.assertEqual(astuple(c), (1, 42))
        self.assertIs(type(astuple(c)), tuple)

    def test_helper_astuple_raises_on_classes(self):
        # astuple() should raise on a class object.
        @dataclass
        class C:
            x: int
            y: int
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            astuple(C)
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            astuple(int)

    def test_helper_astuple_copy_values(self):
        @dataclass
        class C:
            x: int
            y: List[int] = field(default_factory=list)
        initial = []
        c = C(1, initial)
        t = astuple(c)
        self.assertEqual(t[1], initial)
        self.assertIsNot(t[1], initial)
        c = C(1)
        t = astuple(c)
        t[1].append(1)
        self.assertEqual(c.y, [])

    def test_helper_astuple_nested(self):
        @dataclass
        class UserId:
            token: int
            group: int
        @dataclass
        class User:
            name: str
            id: UserId
        u = User('Joe', UserId(123, 1))
        t = astuple(u)
        self.assertEqual(t, ('Joe', (123, 1)))
        self.assertIsNot(astuple(u), astuple(u))
        u.id.group = 2
        self.assertEqual(astuple(u), ('Joe', (123, 2)))

    def test_helper_astuple_builtin_containers(self):
        @dataclass
        class User:
            name: str
            id: int
        @dataclass
        class GroupList:
            id: int
            users: List[User]
        @dataclass
        class GroupTuple:
            id: int
            users: Tuple[User, ...]
        @dataclass
        class GroupDict:
            id: int
            users: Dict[str, User]
        a = User('Alice', 1)
        b = User('Bob', 2)
        gl = GroupList(0, [a, b])
        gt = GroupTuple(0, (a, b))
        gd = GroupDict(0, {'first': a, 'second': b})
        self.assertEqual(astuple(gl), (0, [('Alice', 1), ('Bob', 2)]))
        self.assertEqual(astuple(gt), (0, (('Alice', 1), ('Bob', 2))))
        self.assertEqual(astuple(gd), (0, {'first': ('Alice', 1), 'second': ('Bob', 2)}))

    def test_helper_astuple_builtin_object_containers(self):
        @dataclass
        class Child:
            d: object

        @dataclass
        class Parent:
            child: Child

        self.assertEqual(astuple(Parent(Child([1]))), (([1],),))
        self.assertEqual(astuple(Parent(Child({1: 2}))), (({1: 2},),))

    def test_helper_astuple_factory(self):
        @dataclass
        class C:
            x: int
            y: int
        NT = namedtuple('NT', 'x y')
        def nt(lst):
            return NT(*lst)
        c = C(1, 2)
        t = astuple(c, tuple_factory=nt)
        self.assertEqual(t, NT(1, 2))
        self.assertIsNot(t, astuple(c, tuple_factory=nt))
        c.x = 42
        t = astuple(c, tuple_factory=nt)
        self.assertEqual(t, NT(42, 2))
        self.assertIs(type(t), NT)

    def test_helper_astuple_namedtuple(self):
        T = namedtuple('T', 'a b c')
        @dataclass
        class C:
            x: str
            y: T
        c = C('outer', T(1, C('inner', T(11, 12, 13)), 2))

        t = astuple(c)
        self.assertEqual(t, ('outer', T(1, ('inner', (11, 12, 13)), 2)))

        # Now, using a tuple_factory.  list is convenient here.
        t = astuple(c, tuple_factory=list)
        self.assertEqual(t, ['outer', T(1, ['inner', T(11, 12, 13)], 2)])

    def test_helper_astuple_defaultdict(self):
        # Ensure astuple() does not throw exceptions when a
        # defaultdict is a member of a dataclass
        @dataclass
        class C:
            mp: DefaultDict[str, List]

        dd = defaultdict(list)
        dd["x"].append(12)
        c = C(mp=dd)
        t = astuple(c)

        self.assertEqual(t, ({"x": [12]},))
        self.assertTrue(t[0] is not dd) # make sure defaultdict is copied

    def test_dynamic_class_creation(self):
        cls_dict = {'__annotations__': {'x': int, 'y': int},
                    }

        # Create the class.
        cls = type('C', (), cls_dict)

        # Make it a dataclass.
        cls1 = dataclass(cls)

        self.assertEqual(cls1, cls)
        self.assertEqual(asdict(cls(1, 2)), {'x': 1, 'y': 2})

    def test_dynamic_class_creation_using_field(self):
        cls_dict = {'__annotations__': {'x': int, 'y': int},
                    'y': field(default=5),
                    }

        # Create the class.
        cls = type('C', (), cls_dict)

        # Make it a dataclass.
        cls1 = dataclass(cls)

        self.assertEqual(cls1, cls)
        self.assertEqual(asdict(cls1(1)), {'x': 1, 'y': 5})

    def test_init_in_order(self):
        @dataclass
        class C:
            a: int
            b: int = field()
            c: list = field(default_factory=list, init=False)
            d: list = field(default_factory=list)
            e: int = field(default=4, init=False)
            f: int = 4

        calls = []
        def setattr(self, name, value):
            calls.append((name, value))

        C.__setattr__ = setattr
        c = C(0, 1)
        self.assertEqual(('a', 0), calls[0])
        self.assertEqual(('b', 1), calls[1])
        self.assertEqual(('c', []), calls[2])
        self.assertEqual(('d', []), calls[3])
        self.assertNotIn(('e', 4), calls)
        self.assertEqual(('f', 4), calls[4])

    def test_items_in_dicts(self):
        @dataclass
        class C:
            a: int
            b: list = field(default_factory=list, init=False)
            c: list = field(default_factory=list)
            d: int = field(default=4, init=False)
            e: int = 0

        c = C(0)
        # Class dict
        self.assertNotIn('a', C.__dict__)
        self.assertNotIn('b', C.__dict__)
        self.assertNotIn('c', C.__dict__)
        self.assertIn('d', C.__dict__)
        self.assertEqual(C.d, 4)
        self.assertIn('e', C.__dict__)
        self.assertEqual(C.e, 0)
        # Instance dict
        self.assertIn('a', c.__dict__)
        self.assertEqual(c.a, 0)
        self.assertIn('b', c.__dict__)
        self.assertEqual(c.b, [])
        self.assertIn('c', c.__dict__)
        self.assertEqual(c.c, [])
        self.assertNotIn('d', c.__dict__)
        self.assertIn('e', c.__dict__)
        self.assertEqual(c.e, 0)

    def test_alternate_classmethod_constructor(self):
        # Since __post_init__ can't take params, use a classmethod
        #  alternate constructor.  This is mostly an example to show
        #  how to use this technique.
        @dataclass
        class C:
            x: int
            @classmethod
            def from_file(cls, filename):
                # In a real example, create a new instance
                #  and populate 'x' from contents of a file.
                value_in_file = 20
                return cls(value_in_file)

        self.assertEqual(C.from_file('filename').x, 20)

    def test_field_metadata_default(self):
        # Make sure the default metadata is read-only and of
        #  zero length.
        @dataclass
        class C:
            i: int

        self.assertFalse(fields(C)[0].metadata)
        self.assertEqual(len(fields(C)[0].metadata), 0)
        with self.assertRaisesRegex(TypeError,
                                    'does not support item assignment'):
            fields(C)[0].metadata['test'] = 3

    def test_field_metadata_mapping(self):
        # Make sure only a mapping can be passed as metadata
        #  zero length.
        with self.assertRaises(TypeError):
            @dataclass
            class C:
                i: int = field(metadata=0)

        # Make sure an empty dict works.
        d = {}
        @dataclass
        class C:
            i: int = field(metadata=d)
        self.assertFalse(fields(C)[0].metadata)
        self.assertEqual(len(fields(C)[0].metadata), 0)
        # Update should work (see bpo-35960).
        d['foo'] = 1
        self.assertEqual(len(fields(C)[0].metadata), 1)
        self.assertEqual(fields(C)[0].metadata['foo'], 1)
        with self.assertRaisesRegex(TypeError,
                                    'does not support item assignment'):
            fields(C)[0].metadata['test'] = 3

        # Make sure a non-empty dict works.
        d = {'test': 10, 'bar': '42', 3: 'three'}
        @dataclass
        class C:
            i: int = field(metadata=d)
        self.assertEqual(len(fields(C)[0].metadata), 3)
        self.assertEqual(fields(C)[0].metadata['test'], 10)
        self.assertEqual(fields(C)[0].metadata['bar'], '42')
        self.assertEqual(fields(C)[0].metadata[3], 'three')
        # Update should work.
        d['foo'] = 1
        self.assertEqual(len(fields(C)[0].metadata), 4)
        self.assertEqual(fields(C)[0].metadata['foo'], 1)
        with self.assertRaises(KeyError):
            # Non-existent key.
            fields(C)[0].metadata['baz']
        with self.assertRaisesRegex(TypeError,
                                    'does not support item assignment'):
            fields(C)[0].metadata['test'] = 3

    def test_field_metadata_custom_mapping(self):
        # Try a custom mapping.
        class SimpleNameSpace:
            def __init__(self, **kw):
                self.__dict__.update(kw)

            def __getitem__(self, item):
                if item == 'xyzzy':
                    return 'plugh'
                return getattr(self, item)

            def __len__(self):
                return self.__dict__.__len__()

        @dataclass
        class C:
            i: int = field(metadata=SimpleNameSpace(a=10))

        self.assertEqual(len(fields(C)[0].metadata), 1)
        self.assertEqual(fields(C)[0].metadata['a'], 10)
        with self.assertRaises(AttributeError):
            fields(C)[0].metadata['b']
        # Make sure we're still talking to our custom mapping.
        self.assertEqual(fields(C)[0].metadata['xyzzy'], 'plugh')

    def test_generic_dataclasses(self):
        T = TypeVar('T')

        @dataclass
        class LabeledBox(Generic[T]):
            content: T
            label: str = '<unknown>'

        box = LabeledBox(42)
        self.assertEqual(box.content, 42)
        self.assertEqual(box.label, '<unknown>')

        # Subscripting the resulting class should work, etc.
        Alias = List[LabeledBox[int]]

    def test_generic_extending(self):
        S = TypeVar('S')
        T = TypeVar('T')

        @dataclass
        class Base(Generic[T, S]):
            x: T
            y: S

        @dataclass
        class DataDerived(Base[int, T]):
            new_field: str
        Alias = DataDerived[str]
        c = Alias(0, 'test1', 'test2')
        self.assertEqual(astuple(c), (0, 'test1', 'test2'))

        class NonDataDerived(Base[int, T]):
            def new_method(self):
                return self.y
        Alias = NonDataDerived[float]
        c = Alias(10, 1.0)
        self.assertEqual(c.new_method(), 1.0)

    def test_generic_dynamic(self):
        T = TypeVar('T')

        @dataclass
        class Parent(Generic[T]):
            x: T
        Child = make_dataclass('Child', [('y', T), ('z', Optional[T], None)],
                               bases=(Parent[int], Generic[T]), namespace={'other': 42})
        self.assertIs(Child[int](1, 2).z, None)
        self.assertEqual(Child[int](1, 2, 3).z, 3)
        self.assertEqual(Child[int](1, 2, 3).other, 42)
        # Check that type aliases work correctly.
        Alias = Child[T]
        self.assertEqual(Alias[int](1, 2).x, 1)
        # Check MRO resolution.
        self.assertEqual(Child.__mro__, (Child, Parent, Generic, object))

    def test_dataclasses_pickleable(self):
        global P, Q, R
        @dataclass
        class P:
            x: int
            y: int = 0
        @dataclass
        class Q:
            x: int
            y: int = field(default=0, init=False)
        @dataclass
        class R:
            x: int
            y: List[int] = field(default_factory=list)
        q = Q(1)
        q.y = 2
        samples = [P(1), P(1, 2), Q(1), q, R(1), R(1, [2, 3, 4])]
        for sample in samples:
            for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                with self.subTest(sample=sample, proto=proto):
                    new_sample = pickle.loads(pickle.dumps(sample, proto))
                    self.assertEqual(sample.x, new_sample.x)
                    self.assertEqual(sample.y, new_sample.y)
                    self.assertIsNot(sample, new_sample)
                    new_sample.x = 42
                    another_new_sample = pickle.loads(pickle.dumps(new_sample, proto))
                    self.assertEqual(new_sample.x, another_new_sample.x)
                    self.assertEqual(sample.y, another_new_sample.y)

    def test_dataclasses_qualnames(self):
        @dataclass(order=True, unsafe_hash=True, frozen=True)
        class A:
            x: int
            y: int

        self.assertEqual(A.__init__.__name__, "__init__")
        for function in (
            '__eq__',
            '__lt__',
            '__le__',
            '__gt__',
            '__ge__',
            '__hash__',
            '__init__',
            '__repr__',
            '__setattr__',
            '__delattr__',
        ):
            self.assertEqual(getattr(A, function).__qualname__, f"TestCase.test_dataclasses_qualnames.<locals>.A.{function}")

        with self.assertRaisesRegex(TypeError, r"A\.__init__\(\) missing"):
            A()


class TestFieldNoAnnotation(unittest.TestCase):
    def test_field_without_annotation(self):
        with self.assertRaisesRegex(TypeError,
                                    "'f' is a field but has no type annotation"):
            @dataclass
            class C:
                f = field()

    def test_field_without_annotation_but_annotation_in_base(self):
        @dataclass
        class B:
            f: int

        with self.assertRaisesRegex(TypeError,
                                    "'f' is a field but has no type annotation"):
            # This is still an error: make sure we don't pick up the
            #  type annotation in the base class.
            @dataclass
            class C(B):
                f = field()

    def test_field_without_annotation_but_annotation_in_base_not_dataclass(self):
        # Same test, but with the base class not a dataclass.
        class B:
            f: int

        with self.assertRaisesRegex(TypeError,
                                    "'f' is a field but has no type annotation"):
            # This is still an error: make sure we don't pick up the
            #  type annotation in the base class.
            @dataclass
            class C(B):
                f = field()


class TestDocString(unittest.TestCase):
    def assertDocStrEqual(self, a, b):
        # Because 3.6 and 3.7 differ in how inspect.signature work
        #  (see bpo #32108), for the time being just compare them with
        #  whitespace stripped.
        self.assertEqual(a.replace(' ', ''), b.replace(' ', ''))

    @support.requires_docstrings
    def test_existing_docstring_not_overridden(self):
        @dataclass
        class C:
            """Lorem ipsum"""
            x: int

        self.assertEqual(C.__doc__, "Lorem ipsum")

    def test_docstring_no_fields(self):
        @dataclass
        class C:
            pass

        self.assertDocStrEqual(C.__doc__, "C()")

    def test_docstring_one_field(self):
        @dataclass
        class C:
            x: int

        self.assertDocStrEqual(C.__doc__, "C(x:int)")

    def test_docstring_two_fields(self):
        @dataclass
        class C:
            x: int
            y: int

        self.assertDocStrEqual(C.__doc__, "C(x:int, y:int)")

    def test_docstring_three_fields(self):
        @dataclass
        class C:
            x: int
            y: int
            z: str

        self.assertDocStrEqual(C.__doc__, "C(x:int, y:int, z:str)")

    def test_docstring_one_field_with_default(self):
        @dataclass
        class C:
            x: int = 3

        self.assertDocStrEqual(C.__doc__, "C(x:int=3)")

    def test_docstring_one_field_with_default_none(self):
        @dataclass
        class C:
            x: Union[int, type(None)] = None

        self.assertDocStrEqual(C.__doc__, "C(x:Optional[int]=None)")

    def test_docstring_list_field(self):
        @dataclass
        class C:
            x: List[int]

        self.assertDocStrEqual(C.__doc__, "C(x:List[int])")

    def test_docstring_list_field_with_default_factory(self):
        @dataclass
        class C:
            x: List[int] = field(default_factory=list)

        self.assertDocStrEqual(C.__doc__, "C(x:List[int]=<factory>)")

    def test_docstring_deque_field(self):
        @dataclass
        class C:
            x: deque

        self.assertDocStrEqual(C.__doc__, "C(x:collections.deque)")

    def test_docstring_deque_field_with_default_factory(self):
        @dataclass
        class C:
            x: deque = field(default_factory=deque)

        self.assertDocStrEqual(C.__doc__, "C(x:collections.deque=<factory>)")

    def test_docstring_with_no_signature(self):
        # See https://github.com/python/cpython/issues/103449
        class Meta(type):
            __call__ = dict
        class Base(metaclass=Meta):
            pass

        @dataclass
        class C(Base):
            pass

        self.assertDocStrEqual(C.__doc__, "C")


class TestInit(unittest.TestCase):
    def test_base_has_init(self):
        class B:
            def __init__(self):
                self.z = 100

        # Make sure that declaring this class doesn't raise an error.
        #  The issue is that we can't override __init__ in our class,
        #  but it should be okay to add __init__ to us if our base has
        #  an __init__.
        @dataclass
        class C(B):
            x: int = 0
        c = C(10)
        self.assertEqual(c.x, 10)
        self.assertNotIn('z', vars(c))

        # Make sure that if we don't add an init, the base __init__
        #  gets called.
        @dataclass(init=False)
        class C(B):
            x: int = 10
        c = C()
        self.assertEqual(c.x, 10)
        self.assertEqual(c.z, 100)

    def test_no_init(self):
        @dataclass(init=False)
        class C:
            i: int = 0
        self.assertEqual(C().i, 0)

        @dataclass(init=False)
        class C:
            i: int = 2
            def __init__(self):
                self.i = 3
        self.assertEqual(C().i, 3)

    def test_overwriting_init(self):
        # If the class has __init__, use it no matter the value of
        #  init=.

        @dataclass
        class C:
            x: int
            def __init__(self, x):
                self.x = 2 * x
        self.assertEqual(C(3).x, 6)

        @dataclass(init=True)
        class C:
            x: int
            def __init__(self, x):
                self.x = 2 * x
        self.assertEqual(C(4).x, 8)

        @dataclass(init=False)
        class C:
            x: int
            def __init__(self, x):
                self.x = 2 * x
        self.assertEqual(C(5).x, 10)

    def test_inherit_from_protocol(self):
        # Dataclasses inheriting from protocol should preserve their own `__init__`.
        # See bpo-45081.

        class P(Protocol):
            a: int

        @dataclass
        class C(P):
            a: int

        self.assertEqual(C(5).a, 5)

        @dataclass
        class D(P):
            def __init__(self, a):
                self.a = a * 2

        self.assertEqual(D(5).a, 10)


class TestRepr(unittest.TestCase):
    def test_repr(self):
        @dataclass
        class B:
            x: int

        @dataclass
        class C(B):
            y: int = 10

        o = C(4)
        self.assertEqual(repr(o), 'TestRepr.test_repr.<locals>.C(x=4, y=10)')

        @dataclass
        class D(C):
            x: int = 20
        self.assertEqual(repr(D()), 'TestRepr.test_repr.<locals>.D(x=20, y=10)')

        @dataclass
        class C:
            @dataclass
            class D:
                i: int
            @dataclass
            class E:
                pass
        self.assertEqual(repr(C.D(0)), 'TestRepr.test_repr.<locals>.C.D(i=0)')
        self.assertEqual(repr(C.E()), 'TestRepr.test_repr.<locals>.C.E()')

    def test_no_repr(self):
        # Test a class with no __repr__ and repr=False.
        @dataclass(repr=False)
        class C:
            x: int
        self.assertIn(f'{__name__}.TestRepr.test_no_repr.<locals>.C object at',
                      repr(C(3)))

        # Test a class with a __repr__ and repr=False.
        @dataclass(repr=False)
        class C:
            x: int
            def __repr__(self):
                return 'C-class'
        self.assertEqual(repr(C(3)), 'C-class')

    def test_overwriting_repr(self):
        # If the class has __repr__, use it no matter the value of
        #  repr=.

        @dataclass
        class C:
            x: int
            def __repr__(self):
                return 'x'
        self.assertEqual(repr(C(0)), 'x')

        @dataclass(repr=True)
        class C:
            x: int
            def __repr__(self):
                return 'x'
        self.assertEqual(repr(C(0)), 'x')

        @dataclass(repr=False)
        class C:
            x: int
            def __repr__(self):
                return 'x'
        self.assertEqual(repr(C(0)), 'x')


class TestEq(unittest.TestCase):
    def test_no_eq(self):
        # Test a class with no __eq__ and eq=False.
        @dataclass(eq=False)
        class C:
            x: int
        self.assertNotEqual(C(0), C(0))
        c = C(3)
        self.assertEqual(c, c)

        # Test a class with an __eq__ and eq=False.
        @dataclass(eq=False)
        class C:
            x: int
            def __eq__(self, other):
                return other == 10
        self.assertEqual(C(3), 10)

    def test_overwriting_eq(self):
        # If the class has __eq__, use it no matter the value of
        #  eq=.

        @dataclass
        class C:
            x: int
            def __eq__(self, other):
                return other == 3
        self.assertEqual(C(1), 3)
        self.assertNotEqual(C(1), 1)

        @dataclass(eq=True)
        class C:
            x: int
            def __eq__(self, other):
                return other == 4
        self.assertEqual(C(1), 4)
        self.assertNotEqual(C(1), 1)

        @dataclass(eq=False)
        class C:
            x: int
            def __eq__(self, other):
                return other == 5
        self.assertEqual(C(1), 5)
        self.assertNotEqual(C(1), 1)


class TestOrdering(unittest.TestCase):
    def test_functools_total_ordering(self):
        # Test that functools.total_ordering works with this class.
        @total_ordering
        @dataclass
        class C:
            x: int
            def __lt__(self, other):
                # Perform the test "backward", just to make
                #  sure this is being called.
                return self.x >= other

        self.assertLess(C(0), -1)
        self.assertLessEqual(C(0), -1)
        self.assertGreater(C(0), 1)
        self.assertGreaterEqual(C(0), 1)

    def test_no_order(self):
        # Test that no ordering functions are added by default.
        @dataclass(order=False)
        class C:
            x: int
        # Make sure no order methods are added.
        self.assertNotIn('__le__', C.__dict__)
        self.assertNotIn('__lt__', C.__dict__)
        self.assertNotIn('__ge__', C.__dict__)
        self.assertNotIn('__gt__', C.__dict__)

        # Test that __lt__ is still called
        @dataclass(order=False)
        class C:
            x: int
            def __lt__(self, other):
                return False
        # Make sure other methods aren't added.
        self.assertNotIn('__le__', C.__dict__)
        self.assertNotIn('__ge__', C.__dict__)
        self.assertNotIn('__gt__', C.__dict__)

    def test_overwriting_order(self):
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __lt__'
                                    '.*using functools.total_ordering'):
            @dataclass(order=True)
            class C:
                x: int
                def __lt__(self):
                    pass

        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __le__'
                                    '.*using functools.total_ordering'):
            @dataclass(order=True)
            class C:
                x: int
                def __le__(self):
                    pass

        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __gt__'
                                    '.*using functools.total_ordering'):
            @dataclass(order=True)
            class C:
                x: int
                def __gt__(self):
                    pass

        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __ge__'
                                    '.*using functools.total_ordering'):
            @dataclass(order=True)
            class C:
                x: int
                def __ge__(self):
                    pass

class TestHash(unittest.TestCase):
    def test_unsafe_hash(self):
        @dataclass(unsafe_hash=True)
        class C:
            x: int
            y: str
        self.assertEqual(hash(C(1, 'foo')), hash((1, 'foo')))

    def test_hash_rules(self):
        def non_bool(value):
            # Map to something else that's True, but not a bool.
            if value is None:
                return None
            if value:
                return (3,)
            return 0

        def test(case, unsafe_hash, eq, frozen, with_hash, result):
            with self.subTest(case=case, unsafe_hash=unsafe_hash, eq=eq,
                              frozen=frozen):
                if result != 'exception':
                    if with_hash:
                        @dataclass(unsafe_hash=unsafe_hash, eq=eq, frozen=frozen)
                        class C:
                            def __hash__(self):
                                return 0
                    else:
                        @dataclass(unsafe_hash=unsafe_hash, eq=eq, frozen=frozen)
                        class C:
                            pass

                # See if the result matches what's expected.
                if result == 'fn':
                    # __hash__ contains the function we generated.
                    self.assertIn('__hash__', C.__dict__)
                    self.assertIsNotNone(C.__dict__['__hash__'])

                elif result == '':
                    # __hash__ is not present in our class.
                    if not with_hash:
                        self.assertNotIn('__hash__', C.__dict__)

                elif result == 'none':
                    # __hash__ is set to None.
                    self.assertIn('__hash__', C.__dict__)
                    self.assertIsNone(C.__dict__['__hash__'])

                elif result == 'exception':
                    # Creating the class should cause an exception.
                    #  This only happens with with_hash==True.
                    assert(with_hash)
                    with self.assertRaisesRegex(TypeError, 'Cannot overwrite attribute __hash__'):
                        @dataclass(unsafe_hash=unsafe_hash, eq=eq, frozen=frozen)
                        class C:
                            def __hash__(self):
                                return 0

                else:
                    assert False, f'unknown result {result!r}'

        # There are 8 cases of:
        #  unsafe_hash=True/False
        #  eq=True/False
        #  frozen=True/False
        # And for each of these, a different result if
        #  __hash__ is defined or not.
        for case, (unsafe_hash,  eq,    frozen, res_no_defined_hash, res_defined_hash) in enumerate([
                  (False,        False, False,  '',                  ''),
                  (False,        False, True,   '',                  ''),
                  (False,        True,  False,  'none',              ''),
                  (False,        True,  True,   'fn',                ''),
                  (True,         False, False,  'fn',                'exception'),
                  (True,         False, True,   'fn',                'exception'),
                  (True,         True,  False,  'fn',                'exception'),
                  (True,         True,  True,   'fn',                'exception'),
                  ], 1):
            test(case, unsafe_hash, eq, frozen, False, res_no_defined_hash)
            test(case, unsafe_hash, eq, frozen, True,  res_defined_hash)

            # Test non-bool truth values, too.  This is just to
            #  make sure the data-driven table in the decorator
            #  handles non-bool values.
            test(case, non_bool(unsafe_hash), non_bool(eq), non_bool(frozen), False, res_no_defined_hash)
            test(case, non_bool(unsafe_hash), non_bool(eq), non_bool(frozen), True,  res_defined_hash)


    def test_eq_only(self):
        # If a class defines __eq__, __hash__ is automatically added
        #  and set to None.  This is normal Python behavior, not
        #  related to dataclasses.  Make sure we don't interfere with
        #  that (see bpo=32546).

        @dataclass
        class C:
            i: int
            def __eq__(self, other):
                return self.i == other.i
        self.assertEqual(C(1), C(1))
        self.assertNotEqual(C(1), C(4))

        # And make sure things work in this case if we specify
        #  unsafe_hash=True.
        @dataclass(unsafe_hash=True)
        class C:
            i: int
            def __eq__(self, other):
                return self.i == other.i
        self.assertEqual(C(1), C(1.0))
        self.assertEqual(hash(C(1)), hash(C(1.0)))

        # And check that the classes __eq__ is being used, despite
        #  specifying eq=True.
        @dataclass(unsafe_hash=True, eq=True)
        class C:
            i: int
            def __eq__(self, other):
                return self.i == 3 and self.i == other.i
        self.assertEqual(C(3), C(3))
        self.assertNotEqual(C(1), C(1))
        self.assertEqual(hash(C(1)), hash(C(1.0)))

    def test_0_field_hash(self):
        @dataclass(frozen=True)
        class C:
            pass
        self.assertEqual(hash(C()), hash(()))

        @dataclass(unsafe_hash=True)
        class C:
            pass
        self.assertEqual(hash(C()), hash(()))

    def test_1_field_hash(self):
        @dataclass(frozen=True)
        class C:
            x: int
        self.assertEqual(hash(C(4)), hash((4,)))
        self.assertEqual(hash(C(42)), hash((42,)))

        @dataclass(unsafe_hash=True)
        class C:
            x: int
        self.assertEqual(hash(C(4)), hash((4,)))
        self.assertEqual(hash(C(42)), hash((42,)))

    def test_hash_no_args(self):
        # Test dataclasses with no hash= argument.  This exists to
        #  make sure that if the @dataclass parameter name is changed
        #  or the non-default hashing behavior changes, the default
        #  hashability keeps working the same way.

        class Base:
            def __hash__(self):
                return 301

        # If frozen or eq is None, then use the default value (do not
        #  specify any value in the decorator).
        for frozen, eq,    base,   expected       in [
            (None,  None,  object, 'unhashable'),
            (None,  None,  Base,   'unhashable'),
            (None,  False, object, 'object'),
            (None,  False, Base,   'base'),
            (None,  True,  object, 'unhashable'),
            (None,  True,  Base,   'unhashable'),
            (False, None,  object, 'unhashable'),
            (False, None,  Base,   'unhashable'),
            (False, False, object, 'object'),
            (False, False, Base,   'base'),
            (False, True,  object, 'unhashable'),
            (False, True,  Base,   'unhashable'),
            (True,  None,  object, 'tuple'),
            (True,  None,  Base,   'tuple'),
            (True,  False, object, 'object'),
            (True,  False, Base,   'base'),
            (True,  True,  object, 'tuple'),
            (True,  True,  Base,   'tuple'),
            ]:

            with self.subTest(frozen=frozen, eq=eq, base=base, expected=expected):
                # First, create the class.
                if frozen is None and eq is None:
                    @dataclass
                    class C(base):
                        i: int
                elif frozen is None:
                    @dataclass(eq=eq)
                    class C(base):
                        i: int
                elif eq is None:
                    @dataclass(frozen=frozen)
                    class C(base):
                        i: int
                else:
                    @dataclass(frozen=frozen, eq=eq)
                    class C(base):
                        i: int

                # Now, make sure it hashes as expected.
                if expected == 'unhashable':
                    c = C(10)
                    with self.assertRaisesRegex(TypeError, 'unhashable type'):
                        hash(c)

                elif expected == 'base':
                    self.assertEqual(hash(C(10)), 301)

                elif expected == 'object':
                    # I'm not sure what test to use here.  object's
                    #  hash isn't based on id(), so calling hash()
                    #  won't tell us much.  So, just check the
                    #  function used is object's.
                    self.assertIs(C.__hash__, object.__hash__)

                elif expected == 'tuple':
                    self.assertEqual(hash(C(42)), hash((42,)))

                else:
                    assert False, f'unknown value for expected={expected!r}'


class TestFrozen(unittest.TestCase):
    def test_frozen(self):
        @dataclass(frozen=True)
        class C:
            i: int

        c = C(10)
        self.assertEqual(c.i, 10)
        with self.assertRaises(FrozenInstanceError):
            c.i = 5
        self.assertEqual(c.i, 10)

    def test_frozen_empty(self):
        @dataclass(frozen=True)
        class C:
            pass

        c = C()
        self.assertFalse(hasattr(c, 'i'))
        with self.assertRaises(FrozenInstanceError):
            c.i = 5
        self.assertFalse(hasattr(c, 'i'))
        with self.assertRaises(FrozenInstanceError):
            del c.i

    def test_inherit(self):
        @dataclass(frozen=True)
        class C:
            i: int

        @dataclass(frozen=True)
        class D(C):
            j: int

        d = D(0, 10)
        with self.assertRaises(FrozenInstanceError):
            d.i = 5
        with self.assertRaises(FrozenInstanceError):
            d.j = 6
        self.assertEqual(d.i, 0)
        self.assertEqual(d.j, 10)

    def test_inherit_nonfrozen_from_empty_frozen(self):
        @dataclass(frozen=True)
        class C:
            pass

        with self.assertRaisesRegex(TypeError,
                                    'cannot inherit non-frozen dataclass from a frozen one'):
            @dataclass
            class D(C):
                j: int

    def test_inherit_nonfrozen_from_empty(self):
        @dataclass
        class C:
            pass

        @dataclass
        class D(C):
            j: int

        d = D(3)
        self.assertEqual(d.j, 3)
        self.assertIsInstance(d, C)

    # Test both ways: with an intermediate normal (non-dataclass)
    #  class and without an intermediate class.
    def test_inherit_nonfrozen_from_frozen(self):
        for intermediate_class in [True, False]:
            with self.subTest(intermediate_class=intermediate_class):
                @dataclass(frozen=True)
                class C:
                    i: int

                if intermediate_class:
                    class I(C): pass
                else:
                    I = C

                with self.assertRaisesRegex(TypeError,
                                            'cannot inherit non-frozen dataclass from a frozen one'):
                    @dataclass
                    class D(I):
                        pass

    def test_inherit_frozen_from_nonfrozen(self):
        for intermediate_class in [True, False]:
            with self.subTest(intermediate_class=intermediate_class):
                @dataclass
                class C:
                    i: int

                if intermediate_class:
                    class I(C): pass
                else:
                    I = C

                with self.assertRaisesRegex(TypeError,
                                            'cannot inherit frozen dataclass from a non-frozen one'):
                    @dataclass(frozen=True)
                    class D(I):
                        pass

    def test_inherit_from_normal_class(self):
        for intermediate_class in [True, False]:
            with self.subTest(intermediate_class=intermediate_class):
                class C:
                    pass

                if intermediate_class:
                    class I(C): pass
                else:
                    I = C

                @dataclass(frozen=True)
                class D(I):
                    i: int

            d = D(10)
            with self.assertRaises(FrozenInstanceError):
                d.i = 5

    def test_non_frozen_normal_derived(self):
        # See bpo-32953.

        @dataclass(frozen=True)
        class D:
            x: int
            y: int = 10

        class S(D):
            pass

        s = S(3)
        self.assertEqual(s.x, 3)
        self.assertEqual(s.y, 10)
        s.cached = True

        # But can't change the frozen attributes.
        with self.assertRaises(FrozenInstanceError):
            s.x = 5
        with self.assertRaises(FrozenInstanceError):
            s.y = 5
        self.assertEqual(s.x, 3)
        self.assertEqual(s.y, 10)
        self.assertEqual(s.cached, True)

        with self.assertRaises(FrozenInstanceError):
            del s.x
        self.assertEqual(s.x, 3)
        with self.assertRaises(FrozenInstanceError):
            del s.y
        self.assertEqual(s.y, 10)
        del s.cached
        self.assertFalse(hasattr(s, 'cached'))
        with self.assertRaises(AttributeError) as cm:
            del s.cached
        self.assertNotIsInstance(cm.exception, FrozenInstanceError)

    def test_non_frozen_normal_derived_from_empty_frozen(self):
        @dataclass(frozen=True)
        class D:
            pass

        class S(D):
            pass

        s = S()
        self.assertFalse(hasattr(s, 'x'))
        s.x = 5
        self.assertEqual(s.x, 5)

        del s.x
        self.assertFalse(hasattr(s, 'x'))
        with self.assertRaises(AttributeError) as cm:
            del s.x
        self.assertNotIsInstance(cm.exception, FrozenInstanceError)

    def test_overwriting_frozen(self):
        # frozen uses __setattr__ and __delattr__.
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __setattr__'):
            @dataclass(frozen=True)
            class C:
                x: int
                def __setattr__(self):
                    pass

        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __delattr__'):
            @dataclass(frozen=True)
            class C:
                x: int
                def __delattr__(self):
                    pass

        @dataclass(frozen=False)
        class C:
            x: int
            def __setattr__(self, name, value):
                self.__dict__['x'] = value * 2
        self.assertEqual(C(10).x, 20)

    def test_frozen_hash(self):
        @dataclass(frozen=True)
        class C:
            x: Any

        # If x is immutable, we can compute the hash.  No exception is
        # raised.
        hash(C(3))

        # If x is mutable, computing the hash is an error.
        with self.assertRaisesRegex(TypeError, 'unhashable type'):
            hash(C({}))


class TestSlots(unittest.TestCase):
    def test_simple(self):
        @dataclass
        class C:
            __slots__ = ('x',)
            x: Any

        # There was a bug where a variable in a slot was assumed to
        #  also have a default value (of type
        #  types.MemberDescriptorType).
        with self.assertRaisesRegex(TypeError,
                                    r"__init__\(\) missing 1 required positional argument: 'x'"):
            C()

        # We can create an instance, and assign to x.
        c = C(10)
        self.assertEqual(c.x, 10)
        c.x = 5
        self.assertEqual(c.x, 5)

        # We can't assign to anything else.
        with self.assertRaisesRegex(AttributeError, "'C' object has no attribute 'y'"):
            c.y = 5

    def test_derived_added_field(self):
        # See bpo-33100.
        @dataclass
        class Base:
            __slots__ = ('x',)
            x: Any

        @dataclass
        class Derived(Base):
            x: int
            y: int

        d = Derived(1, 2)
        self.assertEqual((d.x, d.y), (1, 2))

        # We can add a new field to the derived instance.
        d.z = 10

    def test_generated_slots(self):
        @dataclass(slots=True)
        class C:
            x: int
            y: int

        c = C(1, 2)
        self.assertEqual((c.x, c.y), (1, 2))

        c.x = 3
        c.y = 4
        self.assertEqual((c.x, c.y), (3, 4))

        with self.assertRaisesRegex(AttributeError, "'C' object has no attribute 'z'"):
            c.z = 5

    def test_add_slots_when_slots_exists(self):
        with self.assertRaisesRegex(TypeError, '^C already specifies __slots__$'):
            @dataclass(slots=True)
            class C:
                __slots__ = ('x',)
                x: int

    def test_generated_slots_value(self):

        class Root:
            __slots__ = {'x'}

        class Root2(Root):
            __slots__ = {'k': '...', 'j': ''}

        class Root3(Root2):
            __slots__ = ['h']

        class Root4(Root3):
            __slots__ = 'aa'

        @dataclass(slots=True)
        class Base(Root4):
            y: int
            j: str
            h: str

        self.assertEqual(Base.__slots__, ('y', ))

        @dataclass(slots=True)
        class Derived(Base):
            aa: float
            x: str
            z: int
            k: str
            h: str

        self.assertEqual(Derived.__slots__, ('z', ))

        @dataclass
        class AnotherDerived(Base):
            z: int

        self.assertNotIn('__slots__', AnotherDerived.__dict__)

    def test_cant_inherit_from_iterator_slots(self):

        class Root:
            __slots__ = iter(['a'])

        class Root2(Root):
            __slots__ = ('b', )

        with self.assertRaisesRegex(
           TypeError,
            "^Slots of 'Root' cannot be determined"
        ):
            @dataclass(slots=True)
            class C(Root2):
                x: int

    def test_returns_new_class(self):
        class A:
            x: int

        B = dataclass(A, slots=True)
        self.assertIsNot(A, B)

        self.assertFalse(hasattr(A, "__slots__"))
        self.assertTrue(hasattr(B, "__slots__"))

    # Can't be local to test_frozen_pickle.
    @dataclass(frozen=True, slots=True)
    class FrozenSlotsClass:
        foo: str
        bar: int

    @dataclass(frozen=True)
    class FrozenWithoutSlotsClass:
        foo: str
        bar: int

    def test_frozen_pickle(self):
        # bpo-43999

        self.assertEqual(self.FrozenSlotsClass.__slots__, ("foo", "bar"))
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            with self.subTest(proto=proto):
                obj = self.FrozenSlotsClass("a", 1)
                p = pickle.loads(pickle.dumps(obj, protocol=proto))
                self.assertIsNot(obj, p)
                self.assertEqual(obj, p)

                obj = self.FrozenWithoutSlotsClass("a", 1)
                p = pickle.loads(pickle.dumps(obj, protocol=proto))
                self.assertIsNot(obj, p)
                self.assertEqual(obj, p)

    @dataclass(frozen=True, slots=True)
    class FrozenSlotsGetStateClass:
        foo: str
        bar: int

        getstate_called: bool = field(default=False, compare=False)

        def __getstate__(self):
            object.__setattr__(self, 'getstate_called', True)
            return [self.foo, self.bar]

    @dataclass(frozen=True, slots=True)
    class FrozenSlotsSetStateClass:
        foo: str
        bar: int

        setstate_called: bool = field(default=False, compare=False)

        def __setstate__(self, state):
            object.__setattr__(self, 'setstate_called', True)
            object.__setattr__(self, 'foo', state[0])
            object.__setattr__(self, 'bar', state[1])

    @dataclass(frozen=True, slots=True)
    class FrozenSlotsAllStateClass:
        foo: str
        bar: int

        getstate_called: bool = field(default=False, compare=False)
        setstate_called: bool = field(default=False, compare=False)

        def __getstate__(self):
            object.__setattr__(self, 'getstate_called', True)
            return [self.foo, self.bar]

        def __setstate__(self, state):
            object.__setattr__(self, 'setstate_called', True)
            object.__setattr__(self, 'foo', state[0])
            object.__setattr__(self, 'bar', state[1])

    def test_frozen_slots_pickle_custom_state(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            with self.subTest(proto=proto):
                obj = self.FrozenSlotsGetStateClass('a', 1)
                dumped = pickle.dumps(obj, protocol=proto)

                self.assertTrue(obj.getstate_called)
                self.assertEqual(obj, pickle.loads(dumped))

        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            with self.subTest(proto=proto):
                obj = self.FrozenSlotsSetStateClass('a', 1)
                obj2 = pickle.loads(pickle.dumps(obj, protocol=proto))

                self.assertTrue(obj2.setstate_called)
                self.assertEqual(obj, obj2)

        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            with self.subTest(proto=proto):
                obj = self.FrozenSlotsAllStateClass('a', 1)
                dumped = pickle.dumps(obj, protocol=proto)

                self.assertTrue(obj.getstate_called)

                obj2 = pickle.loads(dumped)
                self.assertTrue(obj2.setstate_called)
                self.assertEqual(obj, obj2)

    def test_slots_with_default_no_init(self):
        # Originally reported in bpo-44649.
        @dataclass(slots=True)
        class A:
            a: str
            b: str = field(default='b', init=False)

        obj = A("a")
        self.assertEqual(obj.a, 'a')
        self.assertEqual(obj.b, 'b')

    def test_slots_with_default_factory_no_init(self):
        # Originally reported in bpo-44649.
        @dataclass(slots=True)
        class A:
            a: str
            b: str = field(default_factory=lambda:'b', init=False)

        obj = A("a")
        self.assertEqual(obj.a, 'a')
        self.assertEqual(obj.b, 'b')

    def test_slots_no_weakref(self):
        @dataclass(slots=True)
        class A:
            # No weakref.
            pass

        self.assertNotIn("__weakref__", A.__slots__)
        a = A()
        with self.assertRaisesRegex(TypeError,
                                    "cannot create weak reference"):
            weakref.ref(a)
        with self.assertRaises(AttributeError):
            a.__weakref__

    def test_slots_weakref(self):
        @dataclass(slots=True, weakref_slot=True)
        class A:
            a: int

        self.assertIn("__weakref__", A.__slots__)
        a = A(1)
        a_ref = weakref.ref(a)

        self.assertIs(a.__weakref__, a_ref)

    def test_slots_weakref_base_str(self):
        class Base:
            __slots__ = '__weakref__'

        @dataclass(slots=True)
        class A(Base):
            a: int

        # __weakref__ is in the base class, not A.  But an A is still weakref-able.
        self.assertIn("__weakref__", Base.__slots__)
        self.assertNotIn("__weakref__", A.__slots__)
        a = A(1)
        weakref.ref(a)

    def test_slots_weakref_base_tuple(self):
        # Same as test_slots_weakref_base, but use a tuple instead of a string
        # in the base class.
        class Base:
            __slots__ = ('__weakref__',)

        @dataclass(slots=True)
        class A(Base):
            a: int

        # __weakref__ is in the base class, not A.  But an A is still
        # weakref-able.
        self.assertIn("__weakref__", Base.__slots__)
        self.assertNotIn("__weakref__", A.__slots__)
        a = A(1)
        weakref.ref(a)

    def test_weakref_slot_without_slot(self):
        with self.assertRaisesRegex(TypeError,
                                    "weakref_slot is True but slots is False"):
            @dataclass(weakref_slot=True)
            class A:
                a: int

    def test_weakref_slot_make_dataclass(self):
        A = make_dataclass('A', [('a', int),], slots=True, weakref_slot=True)
        self.assertIn("__weakref__", A.__slots__)
        a = A(1)
        weakref.ref(a)

        # And make sure if raises if slots=True is not given.
        with self.assertRaisesRegex(TypeError,
                                    "weakref_slot is True but slots is False"):
            B = make_dataclass('B', [('a', int),], weakref_slot=True)

    def test_weakref_slot_subclass_weakref_slot(self):
        @dataclass(slots=True, weakref_slot=True)
        class Base:
            field: int

        # A *can* also specify weakref_slot=True if it wants to (gh-93521)
        @dataclass(slots=True, weakref_slot=True)
        class A(Base):
            ...

        # __weakref__ is in the base class, not A.  But an instance of A
        # is still weakref-able.
        self.assertIn("__weakref__", Base.__slots__)
        self.assertNotIn("__weakref__", A.__slots__)
        a = A(1)
        a_ref = weakref.ref(a)
        self.assertIs(a.__weakref__, a_ref)

    def test_weakref_slot_subclass_no_weakref_slot(self):
        @dataclass(slots=True, weakref_slot=True)
        class Base:
            field: int

        @dataclass(slots=True)
        class A(Base):
            ...

        # __weakref__ is in the base class, not A.  Even though A doesn't
        # specify weakref_slot, it should still be weakref-able.
        self.assertIn("__weakref__", Base.__slots__)
        self.assertNotIn("__weakref__", A.__slots__)
        a = A(1)
        a_ref = weakref.ref(a)
        self.assertIs(a.__weakref__, a_ref)

    def test_weakref_slot_normal_base_weakref_slot(self):
        class Base:
            __slots__ = ('__weakref__',)

        @dataclass(slots=True, weakref_slot=True)
        class A(Base):
            field: int

        # __weakref__ is in the base class, not A.  But an instance of
        # A is still weakref-able.
        self.assertIn("__weakref__", Base.__slots__)
        self.assertNotIn("__weakref__", A.__slots__)
        a = A(1)
        a_ref = weakref.ref(a)
        self.assertIs(a.__weakref__, a_ref)


    def test_dataclass_derived_weakref_slot(self):
        class A:
            pass

        @dataclass(slots=True, weakref_slot=True)
        class B(A):
            pass

        B()


class TestDescriptors(unittest.TestCase):
    def test_set_name(self):
        # See bpo-33141.

        # Create a descriptor.
        class D:
            def __set_name__(self, owner, name):
                self.name = name + 'x'
            def __get__(self, instance, owner):
                if instance is not None:
                    return 1
                return self

        # This is the case of just normal descriptor behavior, no
        #  dataclass code is involved in initializing the descriptor.
        @dataclass
        class C:
            c: int=D()
        self.assertEqual(C.c.name, 'cx')

        # Now test with a default value and init=False, which is the
        #  only time this is really meaningful.  If not using
        #  init=False, then the descriptor will be overwritten, anyway.
        @dataclass
        class C:
            c: int=field(default=D(), init=False)
        self.assertEqual(C.c.name, 'cx')
        self.assertEqual(C().c, 1)

    def test_non_descriptor(self):
        # PEP 487 says __set_name__ should work on non-descriptors.
        # Create a descriptor.

        class D:
            def __set_name__(self, owner, name):
                self.name = name + 'x'

        @dataclass
        class C:
            c: int=field(default=D(), init=False)
        self.assertEqual(C.c.name, 'cx')

    def test_lookup_on_instance(self):
        # See bpo-33175.
        class D:
            pass

        d = D()
        # Create an attribute on the instance, not type.
        d.__set_name__ = Mock()

        # Make sure d.__set_name__ is not called.
        @dataclass
        class C:
            i: int=field(default=d, init=False)

        self.assertEqual(d.__set_name__.call_count, 0)

    def test_lookup_on_class(self):
        # See bpo-33175.
        class D:
            pass
        D.__set_name__ = Mock()

        # Make sure D.__set_name__ is called.
        @dataclass
        class C:
            i: int=field(default=D(), init=False)

        self.assertEqual(D.__set_name__.call_count, 1)

    def test_init_calls_set(self):
        class D:
            pass

        D.__set__ = Mock()

        @dataclass
        class C:
            i: D = D()

        # Make sure D.__set__ is called.
        D.__set__.reset_mock()
        c = C(5)
        self.assertEqual(D.__set__.call_count, 1)

    def test_getting_field_calls_get(self):
        class D:
            pass

        D.__set__ = Mock()
        D.__get__ = Mock()

        @dataclass
        class C:
            i: D = D()

        c = C(5)

        # Make sure D.__get__ is called.
        D.__get__.reset_mock()
        value = c.i
        self.assertEqual(D.__get__.call_count, 1)

    def test_setting_field_calls_set(self):
        class D:
            pass

        D.__set__ = Mock()

        @dataclass
        class C:
            i: D = D()

        c = C(5)

        # Make sure D.__set__ is called.
        D.__set__.reset_mock()
        c.i = 10
        self.assertEqual(D.__set__.call_count, 1)

    def test_setting_uninitialized_descriptor_field(self):
        class D:
            pass

        D.__set__ = Mock()

        @dataclass
        class C:
            i: D

        # D.__set__ is not called because there's no D instance to call it on
        D.__set__.reset_mock()
        c = C(5)
        self.assertEqual(D.__set__.call_count, 0)

        # D.__set__ still isn't called after setting i to an instance of D
        # because descriptors don't behave like that when stored as instance vars
        c.i = D()
        c.i = 5
        self.assertEqual(D.__set__.call_count, 0)

    def test_default_value(self):
        class D:
            def __get__(self, instance: Any, owner: object) -> int:
                if instance is None:
                    return 100

                return instance._x

            def __set__(self, instance: Any, value: int) -> None:
                instance._x = value

        @dataclass
        class C:
            i: D = D()

        c = C()
        self.assertEqual(c.i, 100)

        c = C(5)
        self.assertEqual(c.i, 5)

    def test_no_default_value(self):
        class D:
            def __get__(self, instance: Any, owner: object) -> int:
                if instance is None:
                    raise AttributeError()

                return instance._x

            def __set__(self, instance: Any, value: int) -> None:
                instance._x = value

        @dataclass
        class C:
            i: D = D()

        with self.assertRaisesRegex(TypeError, 'missing 1 required positional argument'):
            c = C()

class TestStringAnnotations(unittest.TestCase):
    def test_classvar(self):
        # Some expressions recognized as ClassVar really aren't.  But
        #  if you're using string annotations, it's not an exact
        #  science.
        # These tests assume that both "import typing" and "from
        # typing import *" have been run in this file.
        for typestr in ('ClassVar[int]',
                        'ClassVar [int]',
                        ' ClassVar [int]',
                        'ClassVar',
                        ' ClassVar ',
                        'typing.ClassVar[int]',
                        'typing.ClassVar[str]',
                        ' typing.ClassVar[str]',
                        'typing .ClassVar[str]',
                        'typing. ClassVar[str]',
                        'typing.ClassVar [str]',
                        'typing.ClassVar [ str]',

                        # Not syntactically valid, but these will
                        #  be treated as ClassVars.
                        'typing.ClassVar.[int]',
                        'typing.ClassVar+',
                        ):
            with self.subTest(typestr=typestr):
                @dataclass
                class C:
                    x: typestr

                # x is a ClassVar, so C() takes no args.
                C()

                # And it won't appear in the class's dict because it doesn't
                # have a default.
                self.assertNotIn('x', C.__dict__)

    def test_isnt_classvar(self):
        for typestr in ('CV',
                        't.ClassVar',
                        't.ClassVar[int]',
                        'typing..ClassVar[int]',
                        'Classvar',
                        'Classvar[int]',
                        'typing.ClassVarx[int]',
                        'typong.ClassVar[int]',
                        'dataclasses.ClassVar[int]',
                        'typingxClassVar[str]',
                        ):
            with self.subTest(typestr=typestr):
                @dataclass
                class C:
                    x: typestr

                # x is not a ClassVar, so C() takes one arg.
                self.assertEqual(C(10).x, 10)

    def test_initvar(self):
        # These tests assume that both "import dataclasses" and "from
        #  dataclasses import *" have been run in this file.
        for typestr in ('InitVar[int]',
                        'InitVar [int]'
                        ' InitVar [int]',
                        'InitVar',
                        ' InitVar ',
                        'dataclasses.InitVar[int]',
                        'dataclasses.InitVar[str]',
                        ' dataclasses.InitVar[str]',
                        'dataclasses .InitVar[str]',
                        'dataclasses. InitVar[str]',
                        'dataclasses.InitVar [str]',
                        'dataclasses.InitVar [ str]',

                        # Not syntactically valid, but these will
                        #  be treated as InitVars.
                        'dataclasses.InitVar.[int]',
                        'dataclasses.InitVar+',
                        ):
            with self.subTest(typestr=typestr):
                @dataclass
                class C:
                    x: typestr

                # x is an InitVar, so doesn't create a member.
                with self.assertRaisesRegex(AttributeError,
                                            "object has no attribute 'x'"):
                    C(1).x

    def test_isnt_initvar(self):
        for typestr in ('IV',
                        'dc.InitVar',
                        'xdataclasses.xInitVar',
                        'typing.xInitVar[int]',
                        ):
            with self.subTest(typestr=typestr):
                @dataclass
                class C:
                    x: typestr

                # x is not an InitVar, so there will be a member x.
                self.assertEqual(C(10).x, 10)

    def test_classvar_module_level_import(self):
        from test.test_dataclasses import dataclass_module_1
        from test.test_dataclasses import dataclass_module_1_str
        from test.test_dataclasses import dataclass_module_2
        from test.test_dataclasses import dataclass_module_2_str

        for m in (dataclass_module_1, dataclass_module_1_str,
                  dataclass_module_2, dataclass_module_2_str,
                  ):
            with self.subTest(m=m):
                # There's a difference in how the ClassVars are
                # interpreted when using string annotations or
                # not. See the imported modules for details.
                if m.USING_STRINGS:
                    c = m.CV(10)
                else:
                    c = m.CV()
                self.assertEqual(c.cv0, 20)


                # There's a difference in how the InitVars are
                # interpreted when using string annotations or
                # not. See the imported modules for details.
                c = m.IV(0, 1, 2, 3, 4)

                for field_name in ('iv0', 'iv1', 'iv2', 'iv3'):
                    with self.subTest(field_name=field_name):
                        with self.assertRaisesRegex(AttributeError, f"object has no attribute '{field_name}'"):
                            # Since field_name is an InitVar, it's
                            # not an instance field.
                            getattr(c, field_name)

                if m.USING_STRINGS:
                    # iv4 is interpreted as a normal field.
                    self.assertIn('not_iv4', c.__dict__)
                    self.assertEqual(c.not_iv4, 4)
                else:
                    # iv4 is interpreted as an InitVar, so it
                    # won't exist on the instance.
                    self.assertNotIn('not_iv4', c.__dict__)

    def test_text_annotations(self):
        from test.test_dataclasses import dataclass_textanno

        self.assertEqual(
            get_type_hints(dataclass_textanno.Bar),
            {'foo': dataclass_textanno.Foo})
        self.assertEqual(
            get_type_hints(dataclass_textanno.Bar.__init__),
            {'foo': dataclass_textanno.Foo,
             'return': type(None)})


ByMakeDataClass = make_dataclass('ByMakeDataClass', [('x', int)])
ManualModuleMakeDataClass = make_dataclass('ManualModuleMakeDataClass',
                                           [('x', int)],
                                           module=__name__)
WrongNameMakeDataclass = make_dataclass('Wrong', [('x', int)])
WrongModuleMakeDataclass = make_dataclass('WrongModuleMakeDataclass',
                                          [('x', int)],
                                          module='custom')

class TestMakeDataclass(unittest.TestCase):
    def test_simple(self):
        C = make_dataclass('C',
                           [('x', int),
                            ('y', int, field(default=5))],
                           namespace={'add_one': lambda self: self.x + 1})
        c = C(10)
        self.assertEqual((c.x, c.y), (10, 5))
        self.assertEqual(c.add_one(), 11)


    def test_no_mutate_namespace(self):
        # Make sure a provided namespace isn't mutated.
        ns = {}
        C = make_dataclass('C',
                           [('x', int),
                            ('y', int, field(default=5))],
                           namespace=ns)
        self.assertEqual(ns, {})

    def test_base(self):
        class Base1:
            pass
        class Base2:
            pass
        C = make_dataclass('C',
                           [('x', int)],
                           bases=(Base1, Base2))
        c = C(2)
        self.assertIsInstance(c, C)
        self.assertIsInstance(c, Base1)
        self.assertIsInstance(c, Base2)

    def test_base_dataclass(self):
        @dataclass
        class Base1:
            x: int
        class Base2:
            pass
        C = make_dataclass('C',
                           [('y', int)],
                           bases=(Base1, Base2))
        with self.assertRaisesRegex(TypeError, 'required positional'):
            c = C(2)
        c = C(1, 2)
        self.assertIsInstance(c, C)
        self.assertIsInstance(c, Base1)
        self.assertIsInstance(c, Base2)

        self.assertEqual((c.x, c.y), (1, 2))

    def test_init_var(self):
        def post_init(self, y):
            self.x *= y

        C = make_dataclass('C',
                           [('x', int),
                            ('y', InitVar[int]),
                            ],
                           namespace={'__post_init__': post_init},
                           )
        c = C(2, 3)
        self.assertEqual(vars(c), {'x': 6})
        self.assertEqual(len(fields(c)), 1)

    def test_class_var(self):
        C = make_dataclass('C',
                           [('x', int),
                            ('y', ClassVar[int], 10),
                            ('z', ClassVar[int], field(default=20)),
                            ])
        c = C(1)
        self.assertEqual(vars(c), {'x': 1})
        self.assertEqual(len(fields(c)), 1)
        self.assertEqual(C.y, 10)
        self.assertEqual(C.z, 20)

    def test_other_params(self):
        C = make_dataclass('C',
                           [('x', int),
                            ('y', ClassVar[int], 10),
                            ('z', ClassVar[int], field(default=20)),
                            ],
                           init=False)
        # Make sure we have a repr, but no init.
        self.assertNotIn('__init__', vars(C))
        self.assertIn('__repr__', vars(C))

        # Make sure random other params don't work.
        with self.assertRaisesRegex(TypeError, 'unexpected keyword argument'):
            C = make_dataclass('C',
                               [],
                               xxinit=False)

    def test_no_types(self):
        C = make_dataclass('Point', ['x', 'y', 'z'])
        c = C(1, 2, 3)
        self.assertEqual(vars(c), {'x': 1, 'y': 2, 'z': 3})
        self.assertEqual(C.__annotations__, {'x': 'typing.Any',
                                             'y': 'typing.Any',
                                             'z': 'typing.Any'})

        C = make_dataclass('Point', ['x', ('y', int), 'z'])
        c = C(1, 2, 3)
        self.assertEqual(vars(c), {'x': 1, 'y': 2, 'z': 3})
        self.assertEqual(C.__annotations__, {'x': 'typing.Any',
                                             'y': int,
                                             'z': 'typing.Any'})

    def test_module_attr(self):
        self.assertEqual(ByMakeDataClass.__module__, __name__)
        self.assertEqual(ByMakeDataClass(1).__module__, __name__)
        self.assertEqual(WrongModuleMakeDataclass.__module__, "custom")
        Nested = make_dataclass('Nested', [])
        self.assertEqual(Nested.__module__, __name__)
        self.assertEqual(Nested().__module__, __name__)

    def test_pickle_support(self):
        for klass in [ByMakeDataClass, ManualModuleMakeDataClass]:
            for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                with self.subTest(proto=proto):
                    self.assertEqual(
                        pickle.loads(pickle.dumps(klass, proto)),
                        klass,
                    )
                    self.assertEqual(
                        pickle.loads(pickle.dumps(klass(1), proto)),
                        klass(1),
                    )

    def test_cannot_be_pickled(self):
        for klass in [WrongNameMakeDataclass, WrongModuleMakeDataclass]:
            for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                with self.subTest(proto=proto):
                    with self.assertRaises(pickle.PickleError):
                        pickle.dumps(klass, proto)
                    with self.assertRaises(pickle.PickleError):
                        pickle.dumps(klass(1), proto)

    def test_invalid_type_specification(self):
        for bad_field in [(),
                          (1, 2, 3, 4),
                          ]:
            with self.subTest(bad_field=bad_field):
                with self.assertRaisesRegex(TypeError, r'Invalid field: '):
                    make_dataclass('C', ['a', bad_field])

        # And test for things with no len().
        for bad_field in [float,
                          lambda x:x,
                          ]:
            with self.subTest(bad_field=bad_field):
                with self.assertRaisesRegex(TypeError, r'has no len\(\)'):
                    make_dataclass('C', ['a', bad_field])

    def test_duplicate_field_names(self):
        for field in ['a', 'ab']:
            with self.subTest(field=field):
                with self.assertRaisesRegex(TypeError, 'Field name duplicated'):
                    make_dataclass('C', [field, 'a', field])

    def test_keyword_field_names(self):
        for field in ['for', 'async', 'await', 'as']:
            with self.subTest(field=field):
                with self.assertRaisesRegex(TypeError, 'must not be keywords'):
                    make_dataclass('C', ['a', field])
                with self.assertRaisesRegex(TypeError, 'must not be keywords'):
                    make_dataclass('C', [field])
                with self.assertRaisesRegex(TypeError, 'must not be keywords'):
                    make_dataclass('C', [field, 'a'])

    def test_non_identifier_field_names(self):
        for field in ['()', 'x,y', '*', '2@3', '', 'little johnny tables']:
            with self.subTest(field=field):
                with self.assertRaisesRegex(TypeError, 'must be valid identifiers'):
                    make_dataclass('C', ['a', field])
                with self.assertRaisesRegex(TypeError, 'must be valid identifiers'):
                    make_dataclass('C', [field])
                with self.assertRaisesRegex(TypeError, 'must be valid identifiers'):
                    make_dataclass('C', [field, 'a'])

    def test_underscore_field_names(self):
        # Unlike namedtuple, it's okay if dataclass field names have
        # an underscore.
        make_dataclass('C', ['_', '_a', 'a_a', 'a_'])

    def test_funny_class_names_names(self):
        # No reason to prevent weird class names, since
        # types.new_class allows them.
        for classname in ['()', 'x,y', '*', '2@3', '']:
            with self.subTest(classname=classname):
                C = make_dataclass(classname, ['a', 'b'])
                self.assertEqual(C.__name__, classname)

class TestReplace(unittest.TestCase):
    def test(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int

        c = C(1, 2)
        c1 = replace(c, x=3)
        self.assertEqual(c1.x, 3)
        self.assertEqual(c1.y, 2)

    def test_frozen(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int
            z: int = field(init=False, default=10)
            t: int = field(init=False, default=100)

        c = C(1, 2)
        c1 = replace(c, x=3)
        self.assertEqual((c.x, c.y, c.z, c.t), (1, 2, 10, 100))
        self.assertEqual((c1.x, c1.y, c1.z, c1.t), (3, 2, 10, 100))


        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, x=3, z=20, t=50)
        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, z=20)
            replace(c, x=3, z=20, t=50)

        # Make sure the result is still frozen.
        with self.assertRaisesRegex(FrozenInstanceError, "cannot assign to field 'x'"):
            c1.x = 3

        # Make sure we can't replace an attribute that doesn't exist,
        #  if we're also replacing one that does exist.  Test this
        #  here, because setting attributes on frozen instances is
        #  handled slightly differently from non-frozen ones.
        with self.assertRaisesRegex(TypeError, r"__init__\(\) got an unexpected "
                                             "keyword argument 'a'"):
            c1 = replace(c, x=20, a=5)

    def test_invalid_field_name(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int

        c = C(1, 2)
        with self.assertRaisesRegex(TypeError, r"__init__\(\) got an unexpected "
                                    "keyword argument 'z'"):
            c1 = replace(c, z=3)

    def test_invalid_object(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int

        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            replace(C, x=3)

        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            replace(0, x=3)

    def test_no_init(self):
        @dataclass
        class C:
            x: int
            y: int = field(init=False, default=10)

        c = C(1)
        c.y = 20

        # Make sure y gets the default value.
        c1 = replace(c, x=5)
        self.assertEqual((c1.x, c1.y), (5, 10))

        # Trying to replace y is an error.
        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, x=2, y=30)

        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, y=30)

    def test_classvar(self):
        @dataclass
        class C:
            x: int
            y: ClassVar[int] = 1000

        c = C(1)
        d = C(2)

        self.assertIs(c.y, d.y)
        self.assertEqual(c.y, 1000)

        # Trying to replace y is an error: can't replace ClassVars.
        with self.assertRaisesRegex(TypeError, r"__init__\(\) got an "
                                    "unexpected keyword argument 'y'"):
            replace(c, y=30)

        replace(c, x=5)

    def test_initvar_is_specified(self):
        @dataclass
        class C:
            x: int
            y: InitVar[int]

            def __post_init__(self, y):
                self.x *= y

        c = C(1, 10)
        self.assertEqual(c.x, 10)
        with self.assertRaisesRegex(ValueError, r"InitVar 'y' must be "
                                    "specified with replace()"):
            replace(c, x=3)
        c = replace(c, x=3, y=5)
        self.assertEqual(c.x, 15)

    def test_initvar_with_default_value(self):
        @dataclass
        class C:
            x: int
            y: InitVar[int] = None
            z: InitVar[int] = 42

            def __post_init__(self, y, z):
                if y is not None:
                    self.x += y
                if z is not None:
                    self.x += z

        c = C(x=1, y=10, z=1)
        self.assertEqual(replace(c), C(x=12))
        self.assertEqual(replace(c, y=4), C(x=12, y=4, z=42))
        self.assertEqual(replace(c, y=4, z=1), C(x=12, y=4, z=1))

    def test_recursive_repr(self):
        @dataclass
        class C:
            f: "C"

        c = C(None)
        c.f = c
        self.assertEqual(repr(c), "TestReplace.test_recursive_repr.<locals>.C(f=...)")

    def test_recursive_repr_two_attrs(self):
        @dataclass
        class C:
            f: "C"
            g: "C"

        c = C(None, None)
        c.f = c
        c.g = c
        self.assertEqual(repr(c), "TestReplace.test_recursive_repr_two_attrs"
                                  ".<locals>.C(f=..., g=...)")

    def test_recursive_repr_indirection(self):
        @dataclass
        class C:
            f: "D"

        @dataclass
        class D:
            f: "C"

        c = C(None)
        d = D(None)
        c.f = d
        d.f = c
        self.assertEqual(repr(c), "TestReplace.test_recursive_repr_indirection"
                                  ".<locals>.C(f=TestReplace.test_recursive_repr_indirection"
                                  ".<locals>.D(f=...))")

    def test_recursive_repr_indirection_two(self):
        @dataclass
        class C:
            f: "D"

        @dataclass
        class D:
            f: "E"

        @dataclass
        class E:
            f: "C"

        c = C(None)
        d = D(None)
        e = E(None)
        c.f = d
        d.f = e
        e.f = c
        self.assertEqual(repr(c), "TestReplace.test_recursive_repr_indirection_two"
                                  ".<locals>.C(f=TestReplace.test_recursive_repr_indirection_two"
                                  ".<locals>.D(f=TestReplace.test_recursive_repr_indirection_two"
                                  ".<locals>.E(f=...)))")

    def test_recursive_repr_misc_attrs(self):
        @dataclass
        class C:
            f: "C"
            g: int

        c = C(None, 1)
        c.f = c
        self.assertEqual(repr(c), "TestReplace.test_recursive_repr_misc_attrs"
                                  ".<locals>.C(f=..., g=1)")

    ## def test_initvar(self):
    ##     @dataclass
    ##     class C:
    ##         x: int
    ##         y: InitVar[int]

    ##     c = C(1, 10)
    ##     d = C(2, 20)

    ##     # In our case, replacing an InitVar is a no-op
    ##     self.assertEqual(c, replace(c, y=5))

    ##     replace(c, x=5)

class TestAbstract(unittest.TestCase):
    def test_abc_implementation(self):
        class Ordered(abc.ABC):
            @abc.abstractmethod
            def __lt__(self, other):
                pass

            @abc.abstractmethod
            def __le__(self, other):
                pass

        @dataclass(order=True)
        class Date(Ordered):
            year: int
            month: 'Month'
            day: 'int'

        self.assertFalse(inspect.isabstract(Date))
        self.assertGreater(Date(2020,12,25), Date(2020,8,31))

    def test_maintain_abc(self):
        class A(abc.ABC):
            @abc.abstractmethod
            def foo(self):
                pass

        @dataclass
        class Date(A):
            year: int
            month: 'Month'
            day: 'int'

        self.assertTrue(inspect.isabstract(Date))
        msg = "class Date without an implementation for abstract method 'foo'"
        self.assertRaisesRegex(TypeError, msg, Date)


class TestMatchArgs(unittest.TestCase):
    def test_match_args(self):
        @dataclass
        class C:
            a: int
        self.assertEqual(C(42).__match_args__, ('a',))

    def test_explicit_match_args(self):
        ma = ()
        @dataclass
        class C:
            a: int
            __match_args__ = ma
        self.assertIs(C(42).__match_args__, ma)

    def test_bpo_43764(self):
        @dataclass(repr=False, eq=False, init=False)
        class X:
            a: int
            b: int
            c: int
        self.assertEqual(X.__match_args__, ("a", "b", "c"))

    def test_match_args_argument(self):
        @dataclass(match_args=False)
        class X:
            a: int
        self.assertNotIn('__match_args__', X.__dict__)

        @dataclass(match_args=False)
        class Y:
            a: int
            __match_args__ = ('b',)
        self.assertEqual(Y.__match_args__, ('b',))

        @dataclass(match_args=False)
        class Z(Y):
            z: int
        self.assertEqual(Z.__match_args__, ('b',))

        # Ensure parent dataclass __match_args__ is seen, if child class
        # specifies match_args=False.
        @dataclass
        class A:
            a: int
            z: int
        @dataclass(match_args=False)
        class B(A):
            b: int
        self.assertEqual(B.__match_args__, ('a', 'z'))

    def test_make_dataclasses(self):
        C = make_dataclass('C', [('x', int), ('y', int)])
        self.assertEqual(C.__match_args__, ('x', 'y'))

        C = make_dataclass('C', [('x', int), ('y', int)], match_args=True)
        self.assertEqual(C.__match_args__, ('x', 'y'))

        C = make_dataclass('C', [('x', int), ('y', int)], match_args=False)
        self.assertNotIn('__match__args__', C.__dict__)

        C = make_dataclass('C', [('x', int), ('y', int)], namespace={'__match_args__': ('z',)})
        self.assertEqual(C.__match_args__, ('z',))


class TestKeywordArgs(unittest.TestCase):
    def test_no_classvar_kwarg(self):
        msg = 'field a is a ClassVar but specifies kw_only'
        with self.assertRaisesRegex(TypeError, msg):
            @dataclass
            class A:
                a: ClassVar[int] = field(kw_only=True)

        with self.assertRaisesRegex(TypeError, msg):
            @dataclass
            class A:
                a: ClassVar[int] = field(kw_only=False)

        with self.assertRaisesRegex(TypeError, msg):
            @dataclass(kw_only=True)
            class A:
                a: ClassVar[int] = field(kw_only=False)

    def test_field_marked_as_kwonly(self):
        #######################
        # Using dataclass(kw_only=True)
        @dataclass(kw_only=True)
        class A:
            a: int
        self.assertTrue(fields(A)[0].kw_only)

        @dataclass(kw_only=True)
        class A:
            a: int = field(kw_only=True)
        self.assertTrue(fields(A)[0].kw_only)

        @dataclass(kw_only=True)
        class A:
            a: int = field(kw_only=False)
        self.assertFalse(fields(A)[0].kw_only)

        #######################
        # Using dataclass(kw_only=False)
        @dataclass(kw_only=False)
        class A:
            a: int
        self.assertFalse(fields(A)[0].kw_only)

        @dataclass(kw_only=False)
        class A:
            a: int = field(kw_only=True)
        self.assertTrue(fields(A)[0].kw_only)

        @dataclass(kw_only=False)
        class A:
            a: int = field(kw_only=False)
        self.assertFalse(fields(A)[0].kw_only)

        #######################
        # Not specifying dataclass(kw_only)
        @dataclass
        class A:
            a: int
        self.assertFalse(fields(A)[0].kw_only)

        @dataclass
        class A:
            a: int = field(kw_only=True)
        self.assertTrue(fields(A)[0].kw_only)

        @dataclass
        class A:
            a: int = field(kw_only=False)
        self.assertFalse(fields(A)[0].kw_only)

    def test_match_args(self):
        # kw fields don't show up in __match_args__.
        @dataclass(kw_only=True)
        class C:
            a: int
        self.assertEqual(C(a=42).__match_args__, ())

        @dataclass
        class C:
            a: int
            b: int = field(kw_only=True)
        self.assertEqual(C(42, b=10).__match_args__, ('a',))

    def test_KW_ONLY(self):
        @dataclass
        class A:
            a: int
            _: KW_ONLY
            b: int
            c: int
        A(3, c=5, b=4)
        msg = "takes 2 positional arguments but 4 were given"
        with self.assertRaisesRegex(TypeError, msg):
            A(3, 4, 5)


        @dataclass(kw_only=True)
        class B:
            a: int
            _: KW_ONLY
            b: int
            c: int
        B(a=3, b=4, c=5)
        msg = "takes 1 positional argument but 4 were given"
        with self.assertRaisesRegex(TypeError, msg):
            B(3, 4, 5)

        # Explicitly make a field that follows KW_ONLY be non-keyword-only.
        @dataclass
        class C:
            a: int
            _: KW_ONLY
            b: int
            c: int = field(kw_only=False)
        c = C(1, 2, b=3)
        self.assertEqual(c.a, 1)
        self.assertEqual(c.b, 3)
        self.assertEqual(c.c, 2)
        c = C(1, b=3, c=2)
        self.assertEqual(c.a, 1)
        self.assertEqual(c.b, 3)
        self.assertEqual(c.c, 2)
        c = C(1, b=3, c=2)
        self.assertEqual(c.a, 1)
        self.assertEqual(c.b, 3)
        self.assertEqual(c.c, 2)
        c = C(c=2, b=3, a=1)
        self.assertEqual(c.a, 1)
        self.assertEqual(c.b, 3)
        self.assertEqual(c.c, 2)

    def test_KW_ONLY_as_string(self):
        @dataclass
        class A:
            a: int
            _: 'dataclasses.KW_ONLY'
            b: int
            c: int
        A(3, c=5, b=4)
        msg = "takes 2 positional arguments but 4 were given"
        with self.assertRaisesRegex(TypeError, msg):
            A(3, 4, 5)

    def test_KW_ONLY_twice(self):
        msg = "'Y' is KW_ONLY, but KW_ONLY has already been specified"

        with self.assertRaisesRegex(TypeError, msg):
            @dataclass
            class A:
                a: int
                X: KW_ONLY
                Y: KW_ONLY
                b: int
                c: int

        with self.assertRaisesRegex(TypeError, msg):
            @dataclass
            class A:
                a: int
                X: KW_ONLY
                b: int
                Y: KW_ONLY
                c: int

        with self.assertRaisesRegex(TypeError, msg):
            @dataclass
            class A:
                a: int
                X: KW_ONLY
                b: int
                c: int
                Y: KW_ONLY

        # But this usage is okay, since it's not using KW_ONLY.
        @dataclass
        class A:
            a: int
            _: KW_ONLY
            b: int
            c: int = field(kw_only=True)

        # And if inheriting, it's okay.
        @dataclass
        class A:
            a: int
            _: KW_ONLY
            b: int
            c: int
        @dataclass
        class B(A):
            _: KW_ONLY
            d: int

        # Make sure the error is raised in a derived class.
        with self.assertRaisesRegex(TypeError, msg):
            @dataclass
            class A:
                a: int
                _: KW_ONLY
                b: int
                c: int
            @dataclass
            class B(A):
                X: KW_ONLY
                d: int
                Y: KW_ONLY


    def test_post_init(self):
        @dataclass
        class A:
            a: int
            _: KW_ONLY
            b: InitVar[int]
            c: int
            d: InitVar[int]
            def __post_init__(self, b, d):
                raise CustomError(f'{b=} {d=}')
        with self.assertRaisesRegex(CustomError, 'b=3 d=4'):
            A(1, c=2, b=3, d=4)

        @dataclass
        class B:
            a: int
            _: KW_ONLY
            b: InitVar[int]
            c: int
            d: InitVar[int]
            def __post_init__(self, b, d):
                self.a = b
                self.c = d
        b = B(1, c=2, b=3, d=4)
        self.assertEqual(asdict(b), {'a': 3, 'c': 4})

    def test_defaults(self):
        # For kwargs, make sure we can have defaults after non-defaults.
        @dataclass
        class A:
            a: int = 0
            _: KW_ONLY
            b: int
            c: int = 1
            d: int

        a = A(d=4, b=3)
        self.assertEqual(a.a, 0)
        self.assertEqual(a.b, 3)
        self.assertEqual(a.c, 1)
        self.assertEqual(a.d, 4)

        # Make sure we still check for non-kwarg non-defaults not following
        # defaults.
        err_regex = "non-default argument 'z' follows default argument"
        with self.assertRaisesRegex(TypeError, err_regex):
            @dataclass
            class A:
                a: int = 0
                z: int
                _: KW_ONLY
                b: int
                c: int = 1
                d: int

    def test_make_dataclass(self):
        A = make_dataclass("A", ['a'], kw_only=True)
        self.assertTrue(fields(A)[0].kw_only)

        B = make_dataclass("B",
                           ['a', ('b', int, field(kw_only=False))],
                           kw_only=True)
        self.assertTrue(fields(B)[0].kw_only)
        self.assertFalse(fields(B)[1].kw_only)


if __name__ == '__main__':
    unittest.main()