Standardize type comments to always have one space (#2698)

CHANGES.md

@@ -29,6 +29,7 @@
 
 - Fix type annotation spacing between * and more complex type variable tuple (i.e. `def
   fn(*args: *tuple[*Ts, T]) -> None: pass`) (#4440)
+- Standardize type comments to always have one space (#4467)
 
 ### Caching
 

docs/the_black_code_style/future_style.md

@@ -38,6 +38,9 @@ Currently, the following features are included in the preview style:
   blocks when the line is too long
 - `pep646_typed_star_arg_type_var_tuple`: fix type annotation spacing between * and more
   complex type variable tuple (i.e. `def fn(*args: *tuple[*Ts, T]) -> None: pass`)
+- `type_comments_standardization`: type comments with zero or more empty spaces between
+  `#` and `type:`, or between `type:` and the type itself will be formatted to
+  `# type: (type itself)`.
 
 (labels/unstable-features)=
 

src/black/comments.py

@@ -153,13 +153,20 @@ def make_comment(content: str) -> str:
 
     if content[0] == "#":
         content = content[1:]
+
     NON_BREAKING_SPACE = " "
-    if (
-        content
-        and content[0] == NON_BREAKING_SPACE
-        and not content.lstrip().startswith("type:")
-    ):
+
+    is_type_comment = re.match(r"^\s*type:", content)
+    is_not_type_ignore = re.match(r"^\s*type:(?!\s*ignore\b)", content)
+
+    if content and content[0] == NON_BREAKING_SPACE and not is_type_comment:
         content = " " + content[1:]  # Replace NBSP by a simple space
+    elif is_type_comment and is_not_type_ignore and NON_BREAKING_SPACE not in content:
+        content = content.strip()
+        parts = content.split(":")
+        key = parts[0].strip()  # Remove extra spaces around "type"
+        value = parts[1].strip()  # Remove extra spaces around the value part
+        content = f" {key}: {value}"
     if content and content[0] not in COMMENT_EXCEPTIONS:
         content = " " + content
     return "#" + content

src/black/mode.py

@@ -211,6 +211,7 @@ class Preview(Enum):
     remove_redundant_guard_parens = auto()
     parens_for_long_if_clauses_in_case_block = auto()
     pep646_typed_star_arg_type_var_tuple = auto()
+    type_comments_standardization = auto()
 
 
 UNSTABLE_FEATURES: set[Preview] = {

src/black/nodes.py

@@ -912,10 +912,7 @@ def is_type_comment(leaf: Leaf) -> bool:
     used in modern version of Python, this function may be deprecated in the future."""
     t = leaf.type
     v = leaf.value
-    return (
-        t in {token.COMMENT, STANDALONE_COMMENT}
-        and bool(re.match(r"#\s*type:", v))
-    )
+    return t in {token.COMMENT, STANDALONE_COMMENT} and bool(re.match(r"#\s*type:", v))
 
 
 def is_type_ignore_comment(leaf: Leaf) -> bool:

src/black/resources/black.schema.json

@@ -91,7 +91,8 @@
           "docstring_check_for_newline",
           "remove_redundant_guard_parens",
           "parens_for_long_if_clauses_in_case_block",
-          "pep646_typed_star_arg_type_var_tuple"
+          "pep646_typed_star_arg_type_var_tuple",
+          "type_comments_standardization"
         ]
       },
       "description": "Enable specific features included in the `--unstable` style. Requires `--preview`. No compatibility guarantees are provided on the behavior or existence of any unstable features."

tests/data/cases/type_comment_syntax_error.py

@@ -1,11 +1,57 @@
-def foo(
-    # type: Foo
-    x): pass
+# flags: --preview
+
+
+def f(
+    a,  # type: int
+):
+    pass
+
+
+# test type comments
+def f(a, b, c, d, e, f, g, h, i):
+    # type: (int, int, int, int, int, int, int, int, int) -> None
+    pass
+
+
+def f(
+    a,  #  type :   int
+    b,  #    type :  int
+    c,  #type :   int
+    d,  #   type:   int
+    e,  #              type: int    
+    f,  #  type :  int  
+    g,  #type:int
+    h,  # type: int
+    i,  # type: int
+):
+    # type: (...) -> None
+    pass
+
+
 
 # output
+def f(
+    a,  # type: int
+):
+    pass
+
+
+# test type comments
+def f(a, b, c, d, e, f, g, h, i):
+    # type: (int, int, int, int, int, int, int, int, int) -> None
+    pass
+
 
-def foo(
-    # type: Foo
-    x,
+def f(
+    a,  #  type :   int
+    b,  #    type :  int
+    c,  # type :   int
+    d,  # type: int
+    e,  # type: int
+    f,  #  type :  int
+    g,  # type: int
+    h,  # type: int
+    i,  # type: int
 ):
+    # type: (...) -> None
     pass