Pin comment to single leaf in invisible parens (#872)

diff --git a/black.py b/black.py
index 8318674a722f41fa70e4dfe95febe839dd93c87e..ce27653af14d6451aa23edea57419644a234e8a0 100644 (file)
--- a/black.py
+++ b/black.py
@@ -1282,10 +1282,13 @@ class Line:
         try:
             last_leaf = self.leaves[-1]
             ignored_ids.add(id(last_leaf))
-            if last_leaf.type == token.COMMA:
-                # When trailing commas are inserted by Black for consistency, comments
-                # after the previous last element are not moved (they don't have to,
-                # rendering will still be correct).  So we ignore trailing commas.
+            if last_leaf.type == token.COMMA or (
+                last_leaf.type == token.RPAR and not last_leaf.value
+            ):
+                # When trailing commas or optional parens are inserted by Black for
+                # consistency, comments after the previous last element are not moved
+                # (they don't have to, rendering will still be correct).  So we ignore
+                # trailing commas and invisible.
                 last_leaf = self.leaves[-2]
                 ignored_ids.add(id(last_leaf))
         except IndexError:
@@ -1382,7 +1385,23 @@ class Line:
             comment.prefix = ""
             return False
 
-        self.comments.setdefault(id(self.leaves[-1]), []).append(comment)
+        last_leaf = self.leaves[-1]
+        if (
+            last_leaf.type == token.RPAR
+            and not last_leaf.value
+            and last_leaf.parent
+            and len(list(last_leaf.parent.leaves())) <= 3
+            and not is_type_comment(comment)
+        ):
+            # Comments on an optional parens wrapping a single leaf should belong to
+            # the wrapped node except if it's a type comment. Pinning the comment like
+            # this avoids unstable formatting caused by comment migration.
+            if len(self.leaves) < 2:
+                comment.type = STANDALONE_COMMENT
+                comment.prefix = ""
+                return False
+            last_leaf = self.leaves[-2]
+        self.comments.setdefault(id(last_leaf), []).append(comment)
         return True
 
     def comments_after(self, leaf: Leaf) -> List[Leaf]:

diff --git a/tests/data/cantfit.py b/tests/data/cantfit.py
index 0ab1575ffbcd0e6999e074e01b84ed6020b0efc3..317a38fc6e63484db41fd6809ff59964b14d4331 100644 (file)
--- a/tests/data/cantfit.py
+++ b/tests/data/cantfit.py
@@ -47,8 +47,8 @@ this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_li
     0
 )
 this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_like_it = (
-    1
-)  # with a comment
+    1  # with a comment
+)
 this_is_a_ridiculously_long_name_and_nobody_in_their_right_mind_would_use_one_like_it = [
     1,
     2,

diff --git a/tests/data/comments6.py b/tests/data/comments6.py
index ce17382fb2f928acfcb613327eb90c1166621193..a2cd018adcb77cea5859184cfc3220a0abb45c3f 100644 (file)
--- a/tests/data/comments6.py
+++ b/tests/data/comments6.py
@@ -84,3 +84,6 @@ def func(
         0.0789,
         a[-1],  # type: ignore
     )
+
+
+result = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"  # aaa

diff --git a/tests/data/comments7.py b/tests/data/comments7.py
index 4159d847071382e4fff78054674ca3f362dc25c9..f69863eed47283f4f869e69717332af275fe20a4 100644 (file)
--- a/tests/data/comments7.py
+++ b/tests/data/comments7.py
@@ -23,6 +23,19 @@ from .config import (
     #  DEFAULT_TYPE_ATTRIBUTES,
 )
 
+
+result = 1  # look ma, no comment migration xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+
+result = (
+    1  # look ma, no comment migration xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+)
+
+result = (
+    "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"  # aaa
+)
+
+result = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"  # aaa
+
 # output
 
 from .config import (
@@ -49,3 +62,12 @@ from .config import (
     #  resolve_to_config_type,
     #  DEFAULT_TYPE_ATTRIBUTES,
 )
+
+
+result = 1  # look ma, no comment migration xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+
+result = 1  # look ma, no comment migration xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+
+result = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"  # aaa
+
+result = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"  # aaa