Detect inherited classes (typing.final rule), omit one_ prefix rule when iterating over range() (#2)

* Enhance final class check and for-loop validation logic

* Update test cases for variable usage and dataclass validations

* Rename function to clarify local subclass checking

* Update test cases to properly validate final decorator usage in inheritance hierarchies

* Refactor variable names and simplify range check logic

Author: vrslev

src/community_of_python_flake8_plugin/checks/final_class.py

@@ -40,9 +40,24 @@ def is_model_factory_class(class_node: ast.ClassDef) -> bool:
     return check_inherits_from_bases(class_node, {"ModelFactory", "SQLAlchemyFactory"})
 
 
+def has_local_subclasses(syntax_tree: ast.AST, class_node: ast.ClassDef) -> bool:
+    """Check if there are classes in the same file that inherit from this class."""
+    for one_node in ast.walk(syntax_tree):
+        if isinstance(one_node, ast.ClassDef) and one_node != class_node:
+            for one_base in one_node.bases:
+                # Check for direct class reference: class Child(Parent):
+                if isinstance(one_base, ast.Name) and one_base.id == class_node.name:
+                    return True
+                # Check for attributed class reference: class Child(module.Parent):
+                if isinstance(one_base, ast.Attribute) and one_base.attr == class_node.name:
+                    return True
+    return False
+
+
 @typing.final
 class FinalClassCheck(ast.NodeVisitor):
-    def __init__(self, syntax_tree: ast.AST) -> None:  # noqa: ARG002
+    def __init__(self, syntax_tree: ast.AST) -> None:
+        self.syntax_tree = syntax_tree
         self.violations: list[Violation] = []
 
     def visit_ClassDef(self, ast_node: ast.ClassDef) -> None:
@@ -54,6 +69,10 @@ def _check_final_decorator(self, ast_node: ast.ClassDef) -> None:
         if is_protocol_class(ast_node) or ast_node.name.startswith("Test") or is_model_factory_class(ast_node):
             return
 
+        # If there are classes in this file that inherit from this class, don't require the decorator
+        if has_local_subclasses(self.syntax_tree, ast_node):
+            return
+
         if not contains_final_decorator(ast_node):
             self.violations.append(
                 Violation(

src/community_of_python_flake8_plugin/checks/for_loop_one_prefix.py

@@ -22,14 +22,14 @@ def visit_ListComp(self, ast_node: ast.ListComp) -> None:
         # Validate targets in generators (the 'v' in 'for v in lst')
         for one_comprehension in ast_node.generators:
             if not self._is_partial_unpacking(ast_node.elt, one_comprehension.target):
-                self._validate_comprehension_target(one_comprehension.target)
+                self._validate_comprehension_target(one_comprehension.target, one_comprehension.iter)
         self.generic_visit(ast_node)
 
     def visit_SetComp(self, ast_node: ast.SetComp) -> None:
         # Validate targets in generators (the 'v' in 'for v in lst')
         for one_comprehension in ast_node.generators:
             if not self._is_partial_unpacking(ast_node.elt, one_comprehension.target):
-                self._validate_comprehension_target(one_comprehension.target)
+                self._validate_comprehension_target(one_comprehension.target, one_comprehension.iter)
         self.generic_visit(ast_node)
 
     def visit_DictComp(self, ast_node: ast.DictComp) -> None:
@@ -38,22 +38,22 @@ def visit_DictComp(self, ast_node: ast.DictComp) -> None:
         # key and value are both used
         for one_comprehension in ast_node.generators:
             if not self._is_partial_unpacking_expr_count(2, one_comprehension.target):
-                self._validate_comprehension_target(one_comprehension.target)
+                self._validate_comprehension_target(one_comprehension.target, one_comprehension.iter)
         self.generic_visit(ast_node)
 
     def visit_For(self, ast_node: ast.For) -> None:
         # Validate target variables in regular for-loops
         # Apply same unpacking logic as comprehensions
         # For-loops don't have an expression that references vars
         if not self._is_partial_unpacking_expr_count(1, ast_node.target):
-            self._validate_comprehension_target(ast_node.target)
+            self._validate_comprehension_target(ast_node.target, ast_node.iter)
         self.generic_visit(ast_node)
 
     def visit_GeneratorExp(self, ast_node: ast.GeneratorExp) -> None:
         # Validate targets in generators (the 'v' in 'for v in lst')
         for one_comprehension in ast_node.generators:
             if not self._is_partial_unpacking(ast_node.elt, one_comprehension.target):
-                self._validate_comprehension_target(one_comprehension.target)
+                self._validate_comprehension_target(one_comprehension.target, one_comprehension.iter)
         self.generic_visit(ast_node)
 
     def _is_partial_unpacking(self, expression: ast.expr, target_node: ast.expr) -> bool:
@@ -65,6 +65,22 @@ def _is_partial_unpacking_expr_count(self, expression_count: int, target_node: a
         target_count: typing.Final = self._count_unpacked_vars(target_node)
         return target_count > expression_count and target_count > 1
 
+    def _is_literal_range(self, iter_node: ast.expr) -> bool:
+        """Check if the iteration is over a literal range() call."""
+        # Check for direct range() call
+        if isinstance(iter_node, ast.Call) and isinstance(iter_node.func, ast.Name) and iter_node.func.id == "range":
+            # Check if all arguments are literals (no variables)
+            for one_arg in iter_node.args:
+                if not isinstance(one_arg, (ast.Constant, ast.UnaryOp)):
+                    # If any argument is not a literal, this is not a literal range
+                    # Note: UnaryOp is included to handle negative numbers like -1
+                    return False
+                # For UnaryOp (like -1), check if operand is a literal
+                if isinstance(one_arg, ast.UnaryOp) and not isinstance(one_arg.operand, ast.Constant):
+                    return False
+            return True
+        return False
+
     def _count_referenced_vars(self, expression: ast.expr) -> int:
         """Count how many variables are referenced in the expression."""
         if isinstance(expression, ast.Name):
@@ -83,8 +99,12 @@ def _count_unpacked_vars(self, target_node: ast.expr) -> int:
             return len([one_element for one_element in target_node.elts if isinstance(one_element, ast.Name)])
         return 0
 
-    def _validate_comprehension_target(self, target_node: ast.expr) -> None:
+    def _validate_comprehension_target(self, target_node: ast.expr, iter_node: ast.expr | None = None) -> None:
         """Validate that comprehension target follows the one_ prefix rule."""
+        # Skip validation if iterating over literal range()
+        if iter_node is not None and self._is_literal_range(iter_node):
+            return
+
         # Skip ignored targets (underscore, unpacking)
         if _is_ignored_target(target_node):
             return

tests/test_plugin.py

@@ -422,6 +422,44 @@ def test_variable_usage_validations(input_source: str, expected_output: list[str
             "import typing\nclass MyProtocol(typing.Protocol, object):\n    def fetch_value(self) -> int: ...\n",
             [],
         ),
+        # No violation: Child classes don't require @typing.final since they inherit from other classes
+        (
+            "class ParentClass:\n    pass\n\nclass ChildClass(ParentClass):\n    pass",
+            ["COP012"],  # Only ParentClass should require final decorator, ChildClass inherits so it's exempt
+        ),
+        # No violation: Multiple levels of inheritance
+        (
+            "class GrandParentClass:\n    pass\n\nclass ParentClass(GrandParentClass):\n    pass\n\n"
+            "class ChildClass(ParentClass):\n    pass",
+            ["COP012"],  # Only GrandParentClass requires final decorator, ParentClass and
+            # ChildClass inherit so they're exempt
+        ),
+        # No violation: Child classes with module notation don't require @typing.final
+        (
+            "class ParentClass:\n    pass\n\nclass ChildClass(module.ParentClass):\n    pass",
+            ["COP012"],  # Only ParentClass should require final decorator, ChildClass inherits so it's exempt
+        ),
+        # No violation: Child class properly inherits, parent doesn't need final decorator
+        (
+            "import typing\n\nclass ParentClass:\n    pass\n\n@typing.final\nclass ChildClass(ParentClass):\n    pass",
+            [],  # No violations - ChildClass is properly marked final
+        ),
+        # No violation: Complex inheritance hierarchy with proper final decorators
+        (
+            "import typing\n\n"
+            "class BaseClass:\n    pass\n\n"
+            "class MiddleClass(BaseClass):\n    pass\n\n"
+            "@typing.final\nclass DerivedClass(MiddleClass):\n    pass",
+            [],  # No violations - derived classes are properly marked final
+        ),
+        # No violation: Multiple inheritance with proper final decorators
+        (
+            "import typing\n\n"
+            "class FirstParent:\n    pass\n\n"
+            "class SecondParent:\n    pass\n\n"
+            "@typing.final\nclass ChildClass(FirstParent, SecondParent):\n    pass",
+            [],  # No violations - ChildClass is properly marked final
+        ),
     ],
 )
 def test_class_validations(input_source: str, expected_output: list[str]) -> None:
@@ -605,6 +643,28 @@ def test_dataclass_validations(input_source: str, expected_output: list[str]) ->
         ("for x, y in pairs: pass", []),
         # No violation: Regular for-loop with one_ prefix
         ("for one_x in some_list: pass", []),
+        # No violation: Regular for-loop over literal range() without one_ prefix
+        ("for cur_number in range(10): pass", []),
+        # No violation: Regular for-loop over literal range() with start and stop
+        ("for cur_number in range(5, 10): pass", []),
+        # No violation: Regular for-loop over literal range() with start, stop, and step
+        ("for cur_number in range(0, 10, 2): pass", []),
+        # No violation: Regular for-loop over literal range() with negative values
+        ("for cur_number in range(-5, 5): pass", []),
+        # COP015: Regular for-loop over non-literal range() should still require one_ prefix
+        ("for cur_number in range(some_variable): pass", ["COP015"]),
+        # COP015: Regular for-loop over non-literal range() with multiple variables should still require one_ prefix
+        ("for cur_number in range(start, stop): pass", ["COP015"]),
+        # No violation: List comprehension over literal range() without one_ prefix
+        ("my_result = [cur_number for cur_number in range(10)]", []),
+        # COP015: List comprehension over non-literal range() should still require one_ prefix
+        ("my_result = [cur_number for cur_number in range(variable)]", ["COP015"]),
+        # No violation: Set comprehension over literal range() without one_ prefix
+        ("my_result = {cur_number for cur_number in range(10)}", []),
+        # No violation: Dict comprehension over literal range() without one_ prefix
+        ("my_result = {cur_number: cur_number for cur_number in range(10)}", []),
+        # No violation: Generator expression over literal range() without one_ prefix
+        ("my_result = (cur_number for cur_number in range(10))", []),
     ],
 )
 def test_module_vs_class_level_assignments(input_source: str, expected_output: list[str]) -> None: