Issue wemake-services#1160 (wemake-services#1198)

* Feat: adds stub of the new violation TooManyRaisesViolation

Test: Adds tests for TooManyRaisesViolation which for now are disabled

Test:
* Adds false positivity test with 3 raises in method
* Adds false positivity test with 4 raises in module
* Fixes wrong number of raises in tests
* Fixes string literals in tests to be more pythonic

Fix: fixes test for python 3.8

Docs: Document TooManyRaisesViolation rule. Issue #16 (#20)

Merge branches

Issue #14 (#21)

* Feat: Implement TooManyRaisesViolation rule and config. Issue #14

* Fix: A priori fix for I001 and WPS230 lint failures. Issue #14

* Fix: A priori fix for AssertionError related to tests. Issue #14

* Fix: Modify test_public_attrs_count tests to ignore class _ComplexityCounter. Issue #14

* Fix: Sort imports in test_public_attrs_count. Issue #14

* Fix: Try to avoid lint failures in test_public_attrs_count. Issue #14

* Fix: Undo a few commits and restore defaults. Issue #14

* Refactor: Create class _ComplexityExitMetrics(object). Issue #14

* Fix: (Temporarily) remove decorator @DataClass from class _ComplexityExitMetrics(object). Issue #14

* Fix: Added _ at the beginning of a public attribute in class _ComplexityCounter(object). Issue #14

* Fix: Added = to define a public attribute in class _ComplexityCounter(object). Issue #14

* Fix: Fix various lint errors. Issue #14

* Docs: Changed docs for class _ComplexityExitMetrics(object). Issue #14

* Test: Added Gwin73's fixes for his tests. Issue #14

* Fix: fixes incorrect annotation for test

* Fix for python 3.8

Co-authored-by: Adrian Westerberg <adrianwesterberg@hotmail.com>

Test: Removes integration tests and add unit tests which right now fail

Fix: Fixed a few lint errrors in test_raises_count.py. Issue #15

Issue #15 (#23)

* Test: Created new tests for issue 3. Issue #15

* Test: Modified WPS235 in test_noqa.py. Issue #15

Co-authored-by: iZafiro <60047972+iZafiro@users.noreply.github.com>

Docs: Added WPS235 to CHANGELOG.md. Issue wemake-services#1160

Docs: Changed weird comment in test_raises.py. Issue wemake-services#1160

Doc: Fixes doc

Test: Simplifies integration test

Test: Adds more tests

Fix: Changes code of violation to make merge easier

Refac: changes imports and formatting after rebasing.

Refact issue wemake-services#1160 (#26)

* Refactor issue wemake-services#1160 (#25)

* Refactor: Refactored function.py to include a @DataClass.

* Fix: Added missing comma to function.py.

* Fix: Tried to fix syntax errors.

* Fix: Tried to fix syntax errors.

* Fix: Tried to fix syntax errors.

* Fix: Tried to fix syntax errors.

* Fix: Tried to fix syntax errors.

* Fix: Tried to fix syntax errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix lint errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Tried to fix test errors.

* Fix: Changed wrong frozen=False tag.

* Fix: Changed default to factory.

* Fix: Fixed lint errors.

* Fix: Added defaultDict variable to dataclass.

* Fix: Lint fix.

* Refactor: Finish refactoring dataclass.

* Fix: Fixed lint errors.

* Fix: Fixed lint errors.

* Fix: Fixed test errors.

* Fixes merge

* Fixes merge

* Fixes merge

Co-authored-by: Gwin73 <adrianwesterberg@hotmail.com>
Co-authored-by: sobolevn <mail@sobolevn.me>

CHANGELOG.md

@@ -27,7 +27,8 @@ Semantic versioning in our case means:
 - WPS531: Forbids testing conditions to just return booleans when it is possible to simply return the condition itself
 - Forbids to use unsafe infinite loops
 - Forbids to use raw strings `r''` when not necessary
-- Forbids to use too complex f-strings
+- Forbids to use too complex `f`-strings
+- Forbids to use too many `raise` statements inside a single function
 
 ### Bugfixes
 

tests/fixtures/noqa/noqa.py

@@ -743,3 +743,13 @@ def infinite_loop():
         my_print('forever')
 
 unnecessary_raw_string = r'no backslashes.' # noqa: WPS360
+
+
+def many_raises_function(parameter):  # noqa: WPS238
+    if parameter == 1:
+        raise ValueError('1')
+    if parameter == 2:
+        raise KeyError('2')
+    if parameter == 3:
+        raise IndexError('3')
+    raise TypeError('4')

tests/test_checker/test_noqa.py

@@ -108,6 +108,7 @@
     'WPS235': 1,
     'WPS236': 1,
     'WPS237': 1,
+    'WPS238': 1,
 
     'WPS300': 1,
     'WPS301': 1,

tests/test_visitors/test_ast/test_complexity/test_function/test_arguments_lambda.py

@@ -1,9 +1,11 @@
 import pytest
 
 from wemake_python_styleguide.compat.constants import PY38
+from wemake_python_styleguide.violations.complexity import (
+    TooManyArgumentsViolation,
+)
 from wemake_python_styleguide.visitors.ast.complexity.function import (
     FunctionComplexityVisitor,
-    TooManyArgumentsViolation,
 )
 
 lambda_without_arguments = 'lambda: ...'

tests/test_visitors/test_ast/test_complexity/test_function/test_awaits_count.py

@@ -1,8 +1,10 @@
 import pytest
 
+from wemake_python_styleguide.violations.complexity import (
+    TooManyAwaitsViolation,
+)
 from wemake_python_styleguide.visitors.ast.complexity.function import (
     FunctionComplexityVisitor,
-    TooManyAwaitsViolation,
 )
 
 function_without_awaits = 'def function(): ...'

tests/test_visitors/test_ast/test_complexity/test_function/test_expressions.py

@@ -1,8 +1,10 @@
 import pytest
 
+from wemake_python_styleguide.violations.complexity import (
+    TooManyExpressionsViolation,
+)
 from wemake_python_styleguide.visitors.ast.complexity.function import (
     FunctionComplexityVisitor,
-    TooManyExpressionsViolation,
 )
 
 function_without_expressions = """

tests/test_visitors/test_ast/test_complexity/test_function/test_raises.py

@@ -0,0 +1,137 @@
+# -*- coding: utf-8 -*-
+
+import pytest
+
+from wemake_python_styleguide.violations.complexity import (
+    TooManyRaisesViolation,
+)
+from wemake_python_styleguide.visitors.ast.complexity.function import (
+    FunctionComplexityVisitor,
+)
+
+module_many_raises = """
+if some:
+    raise SomeException
+raise SomeOtherException
+"""
+
+lambda_many_raises = """
+lambda: SomeException if some else SomeOtherException
+"""
+
+function_template = """
+def function(parameter):
+    {0}
+    {1}
+    {2}
+"""
+
+instance_method_template = """
+class Test(object):
+    def method(self, parameter):
+        {0}
+        {1}
+        {2}
+"""
+
+class_method_template = """
+class Test(object):
+    @classmethod
+    def method(cls, parameter):
+        {0}
+        {1}
+        {2}
+"""
+
+static_method_template = """
+class Test(object):
+    @staticmethod
+    def method(parameter):
+        {0}
+        {1}
+        {2}
+"""
+
+
+@pytest.mark.parametrize('code', [
+    module_many_raises,
+    lambda_many_raises,
+])
+def test_asserts_correct_count1(
+    assert_errors,
+    parse_ast_tree,
+    options,
+    code,
+):
+    """Testing that raises counted correctly."""
+    tree = parse_ast_tree(code)
+
+    option_values = options(max_raises=1)
+    visitor = FunctionComplexityVisitor(option_values, tree=tree)
+    visitor.run()
+
+    assert_errors(visitor, [])
+
+
+@pytest.mark.parametrize('context', [
+    function_template,
+    instance_method_template,
+    class_method_template,
+    static_method_template,
+])
+@pytest.mark.parametrize(('first', 'second', 'third'), [
+    ('...', '', ''),
+    ('if some:', '    raise SomeException', 'raise SomeOtherException'),
+    ('def helper():', '    raise SomeException', 'raise SomeOtherException'),
+])
+def test_raises_correct_count2(
+    assert_errors,
+    parse_ast_tree,
+    context,
+    first,
+    second,
+    third,
+    default_options,
+    mode,
+):
+    """Testing that raises are counted correctly."""
+    test_instance = context.format(first, second, third)
+    tree = parse_ast_tree(mode(test_instance))
+
+    visitor = FunctionComplexityVisitor(default_options, tree=tree)
+    visitor.run()
+
+    assert_errors(visitor, [])
+
+
+@pytest.mark.parametrize('context', [
+    function_template,
+    instance_method_template,
+    class_method_template,
+    static_method_template,
+])
+@pytest.mark.parametrize(('first', 'second', 'third'), [
+    ('if some:', '    raise SomeException', 'raise SomeOtherException'),
+    ('def helper():', '    raise SomeException', 'raise SomeOtherException'),
+])
+def test_raises_wrong_count(
+    assert_errors,
+    assert_error_text,
+    parse_ast_tree,
+    options,
+    context,
+    first,
+    second,
+    third,
+    mode,
+):
+    """Testing that many raises raises a warning."""
+    test_instance = function_template.format(first, second, third)
+    tree = parse_ast_tree(mode(test_instance))
+
+    option_values = options(max_raises=1)
+    visitor = FunctionComplexityVisitor(option_values, tree=tree)
+    visitor.run()
+
+    assert_errors(visitor, [TooManyRaisesViolation])
+    assert_error_text(visitor, '2', option_values.max_raises)

tests/test_visitors/test_ast/test_complexity/test_function/test_returns.py

@@ -1,8 +1,10 @@
 import pytest
 
+from wemake_python_styleguide.violations.complexity import (
+    TooManyReturnsViolation,
+)
 from wemake_python_styleguide.visitors.ast.complexity.function import (
     FunctionComplexityVisitor,
-    TooManyReturnsViolation,
 )
 
 function_without_returns = 'def function(): ...'

wemake_python_styleguide/logic/complexity/functions.py

@@ -0,0 +1,43 @@
+from collections import defaultdict
+from typing import DefaultDict, List
+
+import attr
+from typing_extensions import final
+
+from wemake_python_styleguide.types import (
+    AnyFunctionDef,
+    AnyFunctionDefAndLambda,
+)
+
+#: Function complexity counter.
+FunctionCounter = DefaultDict[AnyFunctionDef, int]
+
+#: Function and lambda complexity counter.
+FunctionCounterWithLambda = DefaultDict[AnyFunctionDefAndLambda, int]
+
+#: Function and their variables.
+FunctionNames = DefaultDict[AnyFunctionDef, List[str]]
+
+
+def _default_factory() -> FunctionCounter:
+    """We use a lot of defaultdic magic in these metrics."""
+    return defaultdict(int)
+
+
+@final
+@attr.dataclass(frozen=False)
+class ComplexityMetrics(object):
+    """
+    Complexity metrics for functions.
+
+    We use it as a store of all metrics we count in a function's body.
+    There are quite a lot of them!
+    """
+
+    returns: FunctionCounter = attr.ib(factory=_default_factory)
+    raises: FunctionCounter = attr.ib(factory=_default_factory)
+    awaits: FunctionCounter = attr.ib(factory=_default_factory)
+    asserts: FunctionCounter = attr.ib(factory=_default_factory)
+    expressions: FunctionCounter = attr.ib(factory=_default_factory)
+    arguments: FunctionCounterWithLambda = attr.ib(factory=_default_factory)
+    variables: FunctionNames = attr.ib(factory=lambda: defaultdict(list))

wemake_python_styleguide/options/config.py

@@ -119,6 +119,9 @@
 - ``max-attributes`` - maximum number of public instance attributes,
     defaults to
     :str:`wemake_python_styleguide.options.defaults.MAX_ATTRIBUTES`
+- ``max-raises`` - maximum number of raises in a function,
+    defaults to
+    :str:`wemake_python_styleguide.options.defaults.MAX_RAISES`
 - ``max-cognitive-score`` - maximum amount of cognitive complexity
     per function, defaults to
     :str:`wemake_python_styleguide.options.defaults.MAX_COGNITIVE_SCORE`
@@ -369,6 +372,12 @@ class Configuration(object):
             'Maximum number of public instance attributes.',
         ),
 
+        _Option(
+            '--max-raises',
+            defaults.MAX_RAISES,
+            'Maximum number of raises in a function.',
+        ),
+
         _Option(
             '--max-cognitive-score',
             defaults.MAX_COGNITIVE_SCORE,

wemake_python_styleguide/options/defaults.py

@@ -107,6 +107,9 @@
 #: Maximum number of public attributes in a single class.
 MAX_ATTRIBUTES: Final = 6  # guessed
 
+#: Maximum number of raises in a function.
+MAX_RAISES: Final = 3  # guessed
+
 #: Maximum amount of cognitive complexity per function.
 MAX_COGNITIVE_SCORE: Final = 12  # based on this code statistics
 

wemake_python_styleguide/options/validation.py

@@ -87,6 +87,7 @@ class _ValidatedOptions(object):
     max_asserts: int = attr.ib(validator=[_min_max(min=1)])
     max_access_level: int = attr.ib(validator=[_min_max(min=1)])
     max_attributes: int = attr.ib(validator=[_min_max(min=1)])
+    max_raises: int = attr.ib(validator=[_min_max(min=1)])
     max_cognitive_score: int = attr.ib(validator=[_min_max(min=1)])
     max_cognitive_average: int = attr.ib(validator=[_min_max(min=1)])
     max_call_level: int = attr.ib(validator=[_min_max(min=1)])

wemake_python_styleguide/types.py

@@ -232,6 +232,10 @@ def max_access_level(self) -> int:
     def max_attributes(self) -> int:
         ...
 
+    @property
+    def max_raises(self) -> int:
+        ...
+
     @property
     def max_cognitive_score(self) -> int:
         ...

wemake_python_styleguide/violations/complexity.py

@@ -58,7 +58,7 @@
    TooManyImportedModuleMembersViolation
    TooLongTupleUnpackViolation
    TooComplexFormattedStringViolation
-
+   TooManyRaisesViolation
 
 Module complexity
 -----------------
@@ -100,6 +100,7 @@
 .. autoclass:: TooManyImportedModuleMembersViolation
 .. autoclass:: TooLongTupleUnpackViolation
 .. autoclass:: TooComplexFormattedStringViolation
+.. autoclass:: TooManyRaisesViolation
 
 """
 
@@ -1139,11 +1140,12 @@ class TooManyImportedModuleMembersViolation(ASTViolation):
         Default:
         :str:`wemake_python_styleguide.options.defaults.MAX_IMPORT_FROM_MEMBERS`
 
-    .. versionadded:: 0.14.0
+    .. versionadded:: 0.15.0
 
     """
 
     error_template = 'Found too many imported names from a module: {0}'
+
     code = 235
 
 
@@ -1219,3 +1221,31 @@ class TooComplexFormattedStringViolation(ASTViolation):
 
     error_template = 'Found a too complex `f` string'
     code = 237
+
+
+@final
+class TooManyRaisesViolation(ASTViolation):
+    """
+    Forbids too many ``raise`` statements in a function.
+
+    Reasoning:
+        Too many ``raise`` statements in a function make the code
+        untraceable and overcomplicated.
+
+    Solution:
+        Split the function into smaller functions, such that
+        each of them can raise less errors.
+        Create more standard errors, or use alternative ways to
+        raise them.
+
+    Configuration:
+        This rule is configurable with ``--max-raises``.
+        Default:
+        :str:`wemake_python_styleguide.options.defaults.MAX_RAISES`
+
+    .. versionadded:: 0.15.0
+
+    """
+
+    error_template = 'Found too many raises in a function: {0}'
+    code = 238