Fix crash on # fmt: skip after an opening bracket with a standalone comment

CHANGES.md

@@ -21,6 +21,8 @@
   lengths (#5147)
 - Fix multiline docstring indentation when leading tabs are used inside indented
   docstrings (#5148)
+- Fix a crash on a `# fmt: skip` line placed directly after an opening bracket when a
+  standalone comment is also present among the contents (#5161)
 
 ### Preview style
 

src/black/lines.py

@@ -1271,34 +1271,39 @@ def is_line_short_enough(line: Line, *, mode: Mode, line_str: str = "") -> bool:
 
     max_level_to_update: int | float = math.inf  # track the depth of the MLS
     for i, leaf in enumerate(line.leaves):
+        # A closing bracket continued from a previous line break (e.g. a leftover
+        # `)` left on its own line) is never marked by the bracket tracker, so it
+        # has no `bracket_depth`. Such a leaf is not inside any bracket that opened
+        # on this line, so treat it as depth 0.
+        bracket_depth = getattr(leaf, "bracket_depth", 0)
         if max_level_to_update == math.inf:
             had_comma: int | None = None
-            if leaf.bracket_depth + 1 > len(commas):
+            if bracket_depth + 1 > len(commas):
                 commas.append(0)
-            elif leaf.bracket_depth + 1 < len(commas):
+            elif bracket_depth + 1 < len(commas):
                 had_comma = commas.pop()
             if (
                 had_comma is not None
                 and multiline_string is not None
-                and multiline_string.bracket_depth == leaf.bracket_depth + 1
+                and multiline_string.bracket_depth == bracket_depth + 1
             ):
                 # Have left the level with the MLS, stop tracking commas
-                max_level_to_update = leaf.bracket_depth
+                max_level_to_update = bracket_depth
                 if had_comma > 0:
                     # MLS was in parens with at least one comma - force split
                     return False
 
-        if leaf.bracket_depth <= max_level_to_update and leaf.type == token.COMMA:
+        if bracket_depth <= max_level_to_update and leaf.type == token.COMMA:
             # Inside brackets, ignore trailing comma
             # directly after MLS/MLS-containing expression
             ignore_ctxs: list[LN | None] = [None]
             ignore_ctxs += multiline_string_contexts
-            if (line.inside_brackets or leaf.bracket_depth > 0) and (
+            if (line.inside_brackets or bracket_depth > 0) and (
                 i != len(line.leaves) - 1 or leaf.prev_sibling not in ignore_ctxs
             ):
-                commas[leaf.bracket_depth] += 1
+                commas[bracket_depth] += 1
         if max_level_to_update != math.inf:
-            max_level_to_update = min(max_level_to_update, leaf.bracket_depth)
+            max_level_to_update = min(max_level_to_update, bracket_depth)
 
         if is_multiline_string(leaf):
             if leaf.parent and (

tests/data/cases/fmtskip_after_bracket_with_comment.py

@@ -0,0 +1,50 @@
+# Regression tests for a crash with `AttributeError: 'Leaf' object has no
+# attribute 'bracket_depth'`. A `# fmt: skip` line directly after an opening
+# bracket combined with a standalone comment among the contents used to crash
+# inside `is_line_short_enough`.
+
+from m import (
+# fmt: skip
+    # comment
+    a
+)
+
+f(
+# fmt: skip
+    # comment
+    a
+)
+
+x[
+# fmt: skip
+    # comment
+    a
+]
+
+from m import (  # fmt: skip
+    # comment
+    a
+)
+
+# output
+
+# Regression tests for a crash with `AttributeError: 'Leaf' object has no
+# attribute 'bracket_depth'`. A `# fmt: skip` line directly after an opening
+# bracket combined with a standalone comment among the contents used to crash
+# inside `is_line_short_enough`.
+
+from m import (# fmt: skip  # comment
+ a
+)
+
+f(# fmt: skip  # comment
+ a
+)
+
+x[# fmt: skip  # comment
+ a
+]
+
+from m import (  # fmt: skip  # comment
+ a
+)