Support files with type comment syntax errors (#3594)

CHANGES.md

@@ -38,6 +38,8 @@
 
 <!-- Changes to the parser or to version autodetection -->
 
+- Added support for formatting files with invalid type comments (#3594)
+
 ### Performance
 
 <!-- Changes that improve Black's performance. -->

src/black/parsing.py

@@ -148,24 +148,29 @@ def lib2to3_unparse(node: Node) -> str:
 
 
 def parse_single_version(
-    src: str, version: Tuple[int, int]
+    src: str, version: Tuple[int, int], *, type_comments: bool
 ) -> Union[ast.AST, ast3.AST]:
     filename = "<unknown>"
     # typed-ast is needed because of feature version limitations in the builtin ast 3.8>
     if sys.version_info >= (3, 8) and version >= (3,):
-        return ast.parse(src, filename, feature_version=version, type_comments=True)
+        return ast.parse(
+            src, filename, feature_version=version, type_comments=type_comments
+        )
 
     if _IS_PYPY:
         # PyPy 3.7 doesn't support type comment tracking which is not ideal, but there's
         # not much we can do as typed-ast won't work either.
         if sys.version_info >= (3, 8):
-            return ast3.parse(src, filename, type_comments=True)
+            return ast3.parse(src, filename, type_comments=type_comments)
         else:
             return ast3.parse(src, filename)
     else:
+        if type_comments:
             # Typed-ast is guaranteed to be used here and automatically tracks type
             # comments separately.
             return ast3.parse(src, filename, feature_version=version[1])
+        else:
+            return ast.parse(src, filename)
 
 
 def parse_ast(src: str) -> Union[ast.AST, ast3.AST]:
@@ -175,11 +180,18 @@ def parse_ast(src: str) -> Union[ast.AST, ast3.AST]:
     first_error = ""
     for version in sorted(versions, reverse=True):
         try:
-            return parse_single_version(src, version)
+            return parse_single_version(src, version, type_comments=True)
         except SyntaxError as e:
             if not first_error:
                 first_error = str(e)
 
+    # Try to parse without type comments
+    for version in sorted(versions, reverse=True):
+        try:
+            return parse_single_version(src, version, type_comments=False)
+        except SyntaxError:
+            pass
+
     raise SyntaxError(first_error)
 
 

tests/data/type_comments/type_comment_syntax_error.py

@@ -0,0 +1,11 @@
+def foo(
+    # type: Foo
+    x): pass
+
+# output
+
+def foo(
+    # type: Foo
+    x,
+):
+    pass

tests/test_format.py

@@ -196,3 +196,10 @@ def test_power_op_newline() -> None:
     # requires line_length=0
     source, expected = read_data("miscellaneous", "power_op_newline")
     assert_format(source, expected, mode=black.Mode(line_length=0))
+
+
+def test_type_comment_syntax_error() -> None:
+    """Test that black is able to format python code with type comment syntax errors."""
+    source, expected = read_data("type_comments", "type_comment_syntax_error")
+    assert_format(source, expected)
+    black.assert_equivalent(source, expected)