Fix crash on type comment with trailing space (#3773)

diff --git a/CHANGES.md b/CHANGES.md
index bb304296d63da03c2bc4f5bf8839e536eac02e1d..c7389ce57c6945bbca697976346478c42097b170 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -19,6 +19,8 @@
   under some circumstances. (#3745)
 - Fix a bug where multi-line open parenthesis magic comment like `type: ignore` were not
   correctly parsed (#3740)
+- Fix error in AST validation when Black removes trailing whitespace in a type comment
+  (#3773)
 
 ### Preview style
 

diff --git a/src/black/parsing.py b/src/black/parsing.py
index 455c5eed968af7439bad4a8697e3a6ebe4b23238..e98e019cac6e9a1955f91cc35553a1b7393951dd 100644 (file)
--- a/src/black/parsing.py
+++ b/src/black/parsing.py
@@ -208,15 +208,18 @@ def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
 
         else:
             normalized: object
-            # Constant strings may be indented across newlines, if they are
-            # docstrings; fold spaces after newlines when comparing. Similarly,
-            # trailing and leading space may be removed.
             if (
                 isinstance(node, ast.Constant)
                 and field == "value"
                 and isinstance(value, str)
             ):
+                # Constant strings may be indented across newlines, if they are
+                # docstrings; fold spaces after newlines when comparing. Similarly,
+                # trailing and leading space may be removed.
                 normalized = _normalize("\n", value)
+            elif field == "type_comment" and isinstance(value, str):
+                # Trailing whitespace in type comments is removed.
+                normalized = value.rstrip()
             else:
                 normalized = value
             yield f"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}"

diff --git a/tests/data/simple_cases/comments2.py b/tests/data/simple_cases/comments2.py
index 37e185abf4fca6914402824c11187df030725755..1487dc4b6e2c546a8952fef91315cb57b063e29d 100644 (file)
--- a/tests/data/simple_cases/comments2.py
+++ b/tests/data/simple_cases/comments2.py
@@ -154,6 +154,9 @@ class Test:
                 not parsed.hostname.strip()):
             pass
 
+
+a = "type comment with trailing space"  # type: str   
+
 #######################
 ### SECTION COMMENT ###
 #######################
@@ -332,6 +335,8 @@ class Test:
             pass
 
 
+a = "type comment with trailing space"  # type: str
+
 #######################
 ### SECTION COMMENT ###
 #######################