Don't insert trailing commas after standalone comments

black.py

@@ -1796,9 +1796,10 @@ def append_to_line(leaf: Leaf) -> Iterator[Line]:
             current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets)
     if current_line:
         if (
-            delimiter_priority == COMMA_PRIORITY
+            trailing_comma_safe
+            and delimiter_priority == COMMA_PRIORITY
             and current_line.leaves[-1].type != token.COMMA
-            and trailing_comma_safe
+            and current_line.leaves[-1].type != STANDALONE_COMMENT
         ):
             current_line.append(Leaf(token.COMMA, ","))
         yield current_line

tests/function.py

@@ -47,6 +47,12 @@ def long_lines():
         typedargslist.extend(
             gen_annotated_params(ast_args.kwonlyargs, ast_args.kw_defaults, parameters, implicit_default=True)
         )
+        typedargslist.extend(
+            gen_annotated_params(
+                ast_args.kwonlyargs, ast_args.kw_defaults, parameters, implicit_default=True,
+                # trailing standalone comment
+            )
+        )
     _type_comment_re = re.compile(
         r"""
         ^
@@ -161,6 +167,15 @@ def long_lines():
                 implicit_default=True,
             )
         )
+        typedargslist.extend(
+            gen_annotated_params(
+                ast_args.kwonlyargs,
+                ast_args.kw_defaults,
+                parameters,
+                implicit_default=True,
+                # trailing standalone comment
+            )
+        )
     _type_comment_re = re.compile(
         r"""
         ^