Docstrings shouldn't stop a function being a docstring.

Also, only having a docstring in a function is definitely a stub function.

Author: nhoad

flake8_unused_arguments.py

@@ -159,10 +159,15 @@ def is_stub_function(function: FunctionTypes) -> bool:
     if isinstance(function, ast.Lambda):
         return isinstance(function.body, ast.Ellipsis)
 
-    if (not isinstance(function, ast.Lambda)) and len(function.body) > 1:
-        return False
-
     statement = function.body[0]
+    if isinstance(statement, ast.Expr) and isinstance(statement.value, ast.Str):
+        if len(function.body) > 1:
+            # first statement is a docstring, let's skip it
+            statement = function.body[1]
+        else:
+            # it's a function with only a docstring, that's a stub
+            return True
+
     if isinstance(statement, ast.Pass):
         return True
     if isinstance(statement, ast.Expr) and isinstance(statement.value, ast.Ellipsis):

test_unused_arguments.py

@@ -77,6 +77,12 @@ def test_get_decorator_names(function, expected_result):
 
 
 @pytest.mark.parametrize("function, expected_result", [
+    ("def foo():\n 'with docstring'\n pass", True),
+    ("def foo():\n 'with docstring'", True),
+    ("def foo():\n 'with docstring'\n ...", True),
+    ("def foo():\n 'with docstring'\n return 5", False),
+    ("def foo():\n 'string' + 'with docstring'\n ...", False),
+    ("def foo():\n f = 'string' + 'with docstring'\n ...", False),
     ("def foo(): pass", True),
     ("def foo(): ...", True),
     ("def foo(): return 5", False),