Fix internal error when FORCE_OPTIONAL_PARENTHESES feature is enabled (#2332)

Fixes #2313.

diff --git a/CHANGES.md b/CHANGES.md
index 403723b70cc57b31710609c59509760eacebc475..12e8fccbe4e44516e7429864b8ad5c4511bf5e93 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,6 +5,7 @@
 ### _Black_
 
 - Add primer support and test for code piped into black via STDIN (#2315)
+- Fix internal error when `FORCE_OPTIONAL_PARENTHESES` feature is enabled (#2332)
 
 ## 21.6b0
 

diff --git a/src/black/linegen.py b/src/black/linegen.py
index 3b811f02b7c6383c8aecc1904dee8c1480121a0f..76b553a959a4b770b7f45427e325edd09c95e2ee 100644 (file)
--- a/src/black/linegen.py
+++ b/src/black/linegen.py
@@ -961,14 +961,19 @@ def run_transformer(
 
         result.extend(transform_line(transformed_line, mode=mode, features=features))
 
-    if not (
-        transform.__name__ == "rhs"
-        and line.bracket_tracker.invisible
-        and not any(bracket.value for bracket in line.bracket_tracker.invisible)
-        and not line.contains_multiline_strings()
-        and not result[0].contains_uncollapsable_type_comments()
-        and not result[0].contains_unsplittable_type_ignore()
-        and not is_line_short_enough(result[0], line_length=mode.line_length)
+    if (
+        transform.__name__ != "rhs"
+        or not line.bracket_tracker.invisible
+        or any(bracket.value for bracket in line.bracket_tracker.invisible)
+        or line.contains_multiline_strings()
+        or result[0].contains_uncollapsable_type_comments()
+        or result[0].contains_unsplittable_type_ignore()
+        or is_line_short_enough(result[0], line_length=mode.line_length)
+        # If any leaves have no parents (which _can_ occur since
+        # `transform(line)` potentially destroys the line's underlying node
+        # structure), then we can't proceed. Doing so would cause the below
+        # call to `append_leaves()` to fail.
+        or any(leaf.parent is None for leaf in line.leaves)
     ):
         return result
 

diff --git a/tests/data/long_strings__regression.py b/tests/data/long_strings__regression.py
index 61c28d376ef8519fba80d286f711d735fb827aff..36f323e04d6de18e7ca0041200951706c001b695 100644 (file)
--- a/tests/data/long_strings__regression.py
+++ b/tests/data/long_strings__regression.py
@@ -518,6 +518,12 @@ x = (
     "\N{BLACK RIGHT-POINTING TRIANGLE WITH DOUBLE VERTICAL BAR}\N{VARIATION SELECTOR-16}"
 )
 
+xxxxxx_xxx_xxxx_xx_xxxxx_xxxxxxxx_xxxxxxxx_xxxxxxxxxx_xxxx_xxxx_xxxxx = xxxx.xxxxxx.xxxxxxxxx.xxxxxxxxxxxxxxxxxxxx(
+    xx_xxxxxx={
+        "x3_xxxxxxxx": "xxx3_xxxxx_xxxxxxxx_xxxxxxxx_xxxxxxxxxx_xxxxxxxx_xxxxxx_xxxxxxx",
+    },
+)
+
 
 # output
 
@@ -1150,3 +1156,11 @@ x = (
 x = (
     "\N{BLACK RIGHT-POINTING TRIANGLE WITH DOUBLE VERTICAL BAR}\N{VARIATION SELECTOR-16}"
 )
+
+xxxxxx_xxx_xxxx_xx_xxxxx_xxxxxxxx_xxxxxxxx_xxxxxxxxxx_xxxx_xxxx_xxxxx = xxxx.xxxxxx.xxxxxxxxx.xxxxxxxxxxxxxxxxxxxx(
+    xx_xxxxxx={
+        "x3_xxxxxxxx": (
+            "xxx3_xxxxx_xxxxxxxx_xxxxxxxx_xxxxxxxxxx_xxxxxxxx_xxxxxx_xxxxxxx"
+        ),
+    },
+)