fix: Don't remove comments along with parens (#4218)

Signed-off-by: RedGuy12 <61329810+RedGuy12@users.noreply.github.com>

CHANGES.md

@@ -10,6 +10,9 @@
 
 <!-- Changes that affect Black's stable style -->
 
+- Fixed a bug where comments where mistakenly removed along with redundant parentheses
+  (#4218)
+
 ### Preview style
 
 <!-- Changes that affect Black's preview style -->

src/black/linegen.py

@@ -1553,6 +1553,9 @@ def maybe_make_parens_invisible_in_atom(
             not is_type_ignore_comment_string(middle.prefix.strip())
         ):
             first.value = ""
+            if first.prefix.strip():
+                # Preserve comments before first paren
+                middle.prefix = first.prefix + middle.prefix
             last.value = ""
         maybe_make_parens_invisible_in_atom(
             middle,
@@ -1564,6 +1567,9 @@ def maybe_make_parens_invisible_in_atom(
             # Strip the invisible parens from `middle` by replacing
             # it with the child in-between the invisible parens
             middle.replace(middle.children[1])
+            if middle.children[-1].prefix.strip():
+                # Preserve comments before last paren
+                last.prefix = middle.children[-1].prefix + last.prefix
 
         return False
 

tests/data/cases/comments_in_double_parens.py

@@ -0,0 +1,113 @@
+if (
+    True
+    # sdf
+):
+    print("hw")
+
+if ((
+    True
+    # sdf
+)):
+    print("hw")
+
+if ((
+    # type: ignore
+    True
+)):
+    print("hw")
+
+if ((
+    True
+    # type: ignore
+)):
+    print("hw")
+
+if (
+    # a long comment about
+    # the condition below
+    (a or b)
+):
+    pass
+
+def return_true():
+    return (
+        (
+            True  # this comment gets removed accidentally
+        )
+    )
+
+def return_true():
+    return (True)  # this comment gets removed accidentally
+
+
+if (
+    # huh comment
+    (True)
+):
+    ...
+
+if (
+    # huh
+    (
+        # comment
+        True
+    )
+):
+    ...
+
+
+# output
+
+if (
+    True
+    # sdf
+):
+    print("hw")
+
+if (
+    True
+    # sdf
+):
+    print("hw")
+
+if (
+    # type: ignore
+    True
+):
+    print("hw")
+
+if (
+    True
+    # type: ignore
+):
+    print("hw")
+
+if (
+    # a long comment about
+    # the condition below
+    a
+    or b
+):
+    pass
+
+
+def return_true():
+    return True  # this comment gets removed accidentally
+
+
+def return_true():
+    return True  # this comment gets removed accidentally
+
+
+if (
+    # huh comment
+    True
+):
+    ...
+
+if (
+    # huh
+    # comment
+    True
+):
+    ...