Issue 3292: fix WPS605 false-positive on @staticmethod usage (#3294)

Co-authored-by: sobolevn <[email protected]>

CHANGELOG.md

@@ -32,6 +32,7 @@ This version introduces `wps` CLI tool.
 - Fixes `WPS115` false-positive on `Enum` attributes, #3238
 - Removes duplicated `WPS312`, #3239
 - Fixes `WPS432`, now it shows literal num, #1402
+- Fixes `WPS605` false-positive on `@staticmethod`, #3292
 
 ## 1.0.0
 

tests/test_visitors/test_ast/test_classes/test_methods/test_method_without_arguments.py

@@ -2,6 +2,7 @@
 
 from wemake_python_styleguide.violations.oop import (
     MethodWithoutArgumentsViolation,
+    StaticMethodViolation,
 )
 from wemake_python_styleguide.visitors.ast.classes import WrongMethodVisitor
 
@@ -10,6 +11,12 @@ class Example:
     def some_name({0}): ...
 """
 
+staticmethod_inside_class = """
+class Example:
+    @staticmethod
+    def some_name({0}): ...
+"""
+
 regular_function = 'def some_name({0}): ...'
 
 
@@ -45,10 +52,27 @@ def test_function_without_arguments(
     assert_errors(visitor, [])
 
 
+def test_staticmethod_without_arguments(
+    assert_errors,
+    parse_ast_tree,
+    mode,
+    default_options,
+):
+    """Testing that no arguments for method raises a violation."""
+    tree = parse_ast_tree(mode(staticmethod_inside_class.format('')))
+
+    visitor = WrongMethodVisitor(default_options, tree=tree)
+    visitor.run()
+
+    # will error on @staticmethod presence, but not on arguments absence
+    assert_errors(visitor, [], ignored_types=StaticMethodViolation)
+
+
 @pytest.mark.parametrize(
     'code',
     [
         method_inside_class,
+        staticmethod_inside_class,
         regular_function,
     ],
 )
@@ -78,4 +102,4 @@ def test_with_arguments(
     visitor = WrongMethodVisitor(default_options, tree=tree)
     visitor.run()
 
-    assert_errors(visitor, [])
+    assert_errors(visitor, [], ignored_types=StaticMethodViolation)

wemake_python_styleguide/logic/tree/functions.py

@@ -23,6 +23,8 @@
     'typing_extensions.overload',
 ))
 
+_STATICMETHOD_NAMES: Final = frozenset(('staticmethod',))
+
 
 def given_function_called(
     node: ast.Call,
@@ -103,3 +105,12 @@ def is_overload(node: ast.AST) -> bool:
             if source.node_to_string(decorator) in _OVERLOAD_EXCEPTIONS:
                 return True
     return False
+
+
+def is_staticmethod(node: AnyFunctionDef) -> bool:
+    """Check that function decorated with @staticmethod."""
+    for decorator in node.decorator_list:
+        decorator_name = getattr(decorator, 'id', None)
+        if decorator_name in _STATICMETHOD_NAMES:
+            return True
+    return False

wemake_python_styleguide/violations/oop.py

@@ -250,7 +250,7 @@ class MethodWithoutArgumentsViolation(ASTViolation):
 
     Reasoning:
         Methods without arguments are allowed to be defined,
-        but almost impossible to use.
+        but almost impossible to use, if they are not @staticmethods.
         Furthermore, they don't have an access to ``self``,
         so cannot access the inner state of the object.
         It might be an intentional design or just a typo.
@@ -271,6 +271,8 @@ def method(): ...
 
     .. versionadded:: 0.7.0
     .. versionchanged:: 0.11.0
+    .. versionchanged:: 1.1.0
+       Allows usage of ``@staticmethod`` with no arguments.
 
     """
 

wemake_python_styleguide/visitors/ast/classes.py

@@ -146,14 +146,12 @@ def _check_getters_setters_methods(self, node: ast.ClassDef) -> None:
 class WrongMethodVisitor(base.BaseNodeVisitor):
     """Visits functions, but treats them as methods."""
 
-    _staticmethod_names: ClassVar[frozenset[str]] = frozenset(('staticmethod',))
     _special_async_iter: ClassVar[frozenset[str]] = frozenset(('__aiter__',))
 
     def visit_any_function(self, node: types.AnyFunctionDef) -> None:
         """Checking class methods: async and regular."""
         node_context = nodes.get_context(node)
         if isinstance(node_context, ast.ClassDef):
-            self._check_decorators(node)
             self._check_bound_methods(node)
             self._check_yield_magic_methods(node)
             self._check_async_magic_methods(node)
@@ -163,14 +161,10 @@ def visit_any_function(self, node: types.AnyFunctionDef) -> None:
             )
         self.generic_visit(node)
 
-    def _check_decorators(self, node: types.AnyFunctionDef) -> None:
-        for decorator in node.decorator_list:
-            decorator_name = getattr(decorator, 'id', None)
-            if decorator_name in self._staticmethod_names:
-                self.add_violation(oop.StaticMethodViolation(node))
-
     def _check_bound_methods(self, node: types.AnyFunctionDef) -> None:
-        if not functions.get_all_arguments(node):
+        if functions.is_staticmethod(node):
+            self.add_violation(oop.StaticMethodViolation(node))
+        elif not functions.get_all_arguments(node):
             self.add_violation(
                 oop.MethodWithoutArgumentsViolation(node, text=node.name),
             )