Fix Union detection with custom converters. Part of #4088.

- Introduce `utils.is_union` based on code used by TypeConverter
- Use it also with custom converters to propertly detect Unions
- Fix also subscripted generics with custom converters

atest/robot/keywords/type_conversion/custom_converters.robot

@@ -18,6 +18,9 @@ Class as converter
 Custom in Union
     Check Test Case    ${TESTNAME}
 
+Accept subscripted generics
+    Check Test Case    ${TESTNAME}
+
 Failing conversion
     Check Test Case    ${TESTNAME}
 

atest/testdata/keywords/type_conversion/CustomConverters.py

@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Union
+from typing import List, Union
 
 
 class Number:
@@ -51,6 +51,11 @@ def __init__(self, value: Union[int, str]):
         self.value = value
 
 
+class AcceptSubscriptedGenerics:
+    def __init__(self, numbers: List[int]):
+        self.sum = sum(numbers)
+
+
 class Invalid:
     pass
 
@@ -75,6 +80,7 @@ def __init__(self, arg, *, kwo):
                             FiDate: FiDate.from_string,
                             ClassAsConverter: ClassAsConverter,
                             ClassWithHintsAsConverter: ClassWithHintsAsConverter,
+                            AcceptSubscriptedGenerics: AcceptSubscriptedGenerics,
                             Invalid: 666,
                             TooFewArgs: TooFewArgs,
                             TooManyArgs: TooManyArgs,
@@ -115,6 +121,10 @@ def class_with_hints_as_converter(argument: ClassWithHintsAsConverter, expected=
     assert argument.value == expected
 
 
+def accept_subscripted_generics(argument: AcceptSubscriptedGenerics, expected):
+    assert argument.sum == expected
+
+
 def number_or_int(number: Union[Number, int]):
     assert number == 1
 

atest/testdata/keywords/type_conversion/custom_converters.robot

@@ -38,6 +38,9 @@ Custom in Union
     Int or number    1
     Int or number    one
 
+Accept subscripted generics
+    Accept subscripted generics    ${{[1, 2, 3]}}    ${6}
+
 Failing conversion
     [Template]    Conversion should fail
     Number     wrong         type=Number     error=ValueError: Don't know number 'wrong'.

src/robot/running/arguments/customconverters.py

@@ -13,7 +13,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-from robot.utils import getdoc, type_name
+from robot.utils import getdoc, is_union, type_name
 
 from .argumentparser import PythonArgumentParser
 
@@ -83,9 +83,10 @@ def for_converter(cls, type_, converter):
         arg_type = spec.types.get(spec.positional[0])
         if arg_type is None:
             accepts = ()
-        # FIXME: This Union detection is faulty. Also others have __args__!!
-        elif hasattr(arg_type, '__args__'):
+        elif is_union(arg_type):
             accepts = arg_type.__args__
+        elif hasattr(arg_type, '__origin__'):
+            accepts = (arg_type.__origin__,)
         else:
             accepts = (arg_type,)
         return cls(type_, converter, accepts)

src/robot/running/arguments/typeconverters.py

@@ -15,10 +15,6 @@
 
 from ast import literal_eval
 from collections import abc, OrderedDict
-try:
-    from types import UnionType
-except ImportError:    # Python < 3.10
-    UnionType = ()
 from typing import Union
 from datetime import datetime, date, timedelta
 from decimal import InvalidOperation, Decimal
@@ -27,7 +23,7 @@
 
 from robot.libraries.DateTime import convert_date, convert_time
 from robot.utils import (FALSE_STRINGS, TRUE_STRINGS, eq, get_error_message,
-                         is_string, safe_str, seq2str, type_name)
+                         is_string, is_union, safe_str, seq2str, type_name)
 
 from .typeinfo import TypeInfo
 
@@ -498,8 +494,7 @@ def type_name(self):
 
     @classmethod
     def handles(cls, type_):
-        return (isinstance(type_, (UnionType, tuple))
-                or getattr(type_, '__origin__', None) is Union)
+        return is_union(type_, allow_tuple=True)
 
     def _handles_value(self, value):
         return True

src/robot/utils/__init__.py

@@ -64,7 +64,7 @@
                         parse_time)
 from .robottypes import (FALSE_STRINGS, TRUE_STRINGS, is_bytes, is_dict_like,
                          is_falsy, is_integer, is_list_like, is_number, is_pathlike,
-                         is_string, is_truthy, type_name, typeddict_types)
+                         is_string, is_truthy, is_union, type_name, typeddict_types)
 from .setter import setter, SetterAwareType
 from .sortable import Sortable
 from .text import (cut_assign_value, cut_long_message, format_assign_message,

src/robot/utils/robottypes.py

@@ -17,6 +17,11 @@
 from collections import UserString
 from io import IOBase
 from os import PathLike
+try:
+    from types import UnionType
+except ImportError:    # Python < 3.10
+    UnionType = ()
+from typing import Union
 try:
     from typing import TypedDict
 except ImportError:    # Python < 3.8
@@ -67,6 +72,12 @@ def is_dict_like(item):
     return isinstance(item, Mapping)
 
 
+def is_union(item, allow_tuple=False):
+    return (isinstance(item, UnionType)
+            or getattr(item, '__origin__', None) is Union
+            or allow_tuple and isinstance(item, tuple))
+
+
 def type_name(item, capitalize=False):
     if getattr(item, '__origin__', None):
         item = item.__origin__

utest/utils/test_robottypes.py

@@ -6,7 +6,7 @@
 from typing import Any, Dict, List, Optional, Set, Tuple, Union
 
 from robot.utils import (is_bytes, is_falsy, is_dict_like, is_list_like,
-                         is_string, is_truthy, type_name)
+                         is_string, is_truthy, is_union, PY_VERSION, type_name)
 from robot.utils.asserts import assert_equal, assert_true
 
 
@@ -26,7 +26,7 @@ def generator():
     yield 'generated'
 
 
-class TestStringsAndBytes(unittest.TestCase):
+class TestIsMisc(unittest.TestCase):
 
     def test_strings(self):
         for thing in ['string', 'hyvä', '']:
@@ -38,6 +38,18 @@ def test_bytes(self):
             assert_equal(is_bytes(thing), True, thing)
             assert_equal(is_string(thing), False, thing)
 
+    def test_is_union(self):
+        assert is_union(Union[int, str])
+        assert is_union(Union[int, str], allow_tuple=True)
+        assert not is_union((int, str))
+        assert is_union((int, str), allow_tuple=True)
+        if PY_VERSION >= (3, 10):
+            assert is_union(eval('int | str'))
+            assert is_union(eval('int | str'), allow_tuple=True)
+        for not_union in 'string', 3, [int, str], list, List[int]:
+            assert not is_union(not_union)
+            assert not is_union(not_union, allow_tuple=True)
+
 
 class TestListLike(unittest.TestCase):
 
@@ -120,14 +132,11 @@ def test_file(self):
             assert_equal(type_name(f), 'file')
 
     def test_custom_objects(self):
-        class NewStyle: pass
-        class OldStyle: pass
+        class CamelCase: pass
         class lower: pass
-        for item, exp in [(NewStyle(), 'NewStyle'),
-                          (OldStyle(), 'OldStyle'),
+        for item, exp in [(CamelCase(), 'CamelCase'),
                           (lower(), 'lower'),
-                          (NewStyle, 'NewStyle'),
-                          (OldStyle, 'OldStyle')]:
+                          (CamelCase, 'CamelCase')]:
             assert_equal(type_name(item), exp)
 
     def test_strip_underscores(self):