introduce A005 for lambda

Author: cielavenir

flake8_builtins.py

@@ -12,6 +12,7 @@ class BuiltinsChecker:
     argument_msg = 'A002 argument "{0}" is shadowing a Python builtin'
     class_attribute_msg = 'A003 class attribute "{0}" is shadowing a Python builtin'
     import_msg = 'A004 import statement "{0}" is shadowing a Python builtin'
+    lambda_argument_msg = 'A005 lambda argument "{0}" is shadowing a Python builtin'
 
     names = []
     ignore_list = {
@@ -58,7 +59,7 @@ def run(self):
             for child in ast.iter_child_nodes(statement):
                 child.__flake8_builtins_parent = statement
 
-        function_nodes = [ast.FunctionDef, ast.Lambda]
+        function_nodes = [ast.FunctionDef]
         if getattr(ast, 'AsyncFunctionDef', None):
             function_nodes.append(ast.AsyncFunctionDef)
         function_nodes = tuple(function_nodes)
@@ -88,6 +89,9 @@ def run(self):
             elif isinstance(statement, function_nodes):
                 value = self.check_function_definition(statement)
 
+            elif isinstance(statement, ast.Lambda):
+                value = self.check_lambda_definition(statement)
+
             elif isinstance(statement, for_nodes):
                 value = self.check_for_loop(statement)
 
@@ -136,7 +140,7 @@ def check_assignment(self, statement):
                     stack.extend(list(item.value.elts))
 
     def check_function_definition(self, statement):
-        if not isinstance(statement, ast.Lambda) and statement.name in self.names:
+        if statement.name in self.names:
             msg = self.assign_msg
             if type(statement.__flake8_builtins_parent) is ast.ClassDef:
                 msg = self.class_attribute_msg
@@ -156,6 +160,20 @@ def check_function_definition(self, statement):
                     variable=arg.arg,
                 )
 
+    def check_lambda_definition(self, statement):
+        all_arguments = []
+        all_arguments.extend(statement.args.args)
+        all_arguments.extend(getattr(statement.args, 'kwonlyargs', []))
+        all_arguments.extend(getattr(statement.args, 'posonlyargs', []))
+
+        for arg in all_arguments:
+            if isinstance(arg, ast.arg) and arg.arg in self.names:
+                yield self.error(
+                    arg,
+                    message=self.lambda_argument_msg,
+                    variable=arg.arg,
+                )
+
     def check_for_loop(self, statement):
         stack = [statement.target]
         while stack:

run_tests.py

@@ -142,7 +142,7 @@ def bla(list):
 
 def test_lambda_argument_message():
     source = 'takefirst = lambda list: list[0]'
-    check_code(source, 'A002')
+    check_code(source, 'A005')
 
 
 def test_keyword_argument_message():
@@ -171,6 +171,15 @@ def bla(list, /):
     """
     check_code(source, 'A002')
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 8),
+    reason='This syntax is only valid in Python 3.8+',
+)
+def test_lambda_posonly_argument_message():
+    source = """
+    takefirst = lambda list, /: list[0]
+    """
+    check_code(source, 'A005')
 
 def test_no_error():
     source = """def bla(first):\n    b = 4"""