Don't split on pragma markers

Author: zsol

CHANGES.md

@@ -9,6 +9,7 @@
 ### Stable style
 
 <!-- Changes that affect Black's stable style -->
+- Treat lines marked with common pragma markers (e.g. `# noqa`) the same as `# type: ignore` -- don't split them, but allow merging (#4039)
 
 ### Preview style
 

src/black/comments.py

@@ -6,6 +6,7 @@
 from black.mode import Mode, Preview
 from black.nodes import (
     CLOSING_BRACKETS,
+    PRAGMA_COMMENT_MARKER,
     STANDALONE_COMMENT,
     WHITESPACE,
     container_of,
@@ -333,7 +334,7 @@ def contains_pragma_comment(comment_list: List[Leaf]) -> bool:
         pylint).
     """
     for comment in comment_list:
-        if comment.value.startswith(("# type:", "# noqa", "# pylint:")):
+        if comment.value.startswith(PRAGMA_COMMENT_MARKER):
             return True
 
     return False

src/black/linegen.py

@@ -47,11 +47,11 @@
     is_name_token,
     is_one_sequence_between,
     is_one_tuple,
+    is_pragma_comment_string,
     is_rpar_token,
     is_stub_body,
     is_stub_suite,
     is_tuple_containing_walrus,
-    is_type_ignore_comment_string,
     is_vararg,
     is_walrus_assignment,
     is_yield,
@@ -1521,7 +1521,7 @@ def maybe_make_parens_invisible_in_atom(
         if (
             # If the prefix of `middle` includes a type comment with
             # ignore annotation, then we do not remove the parentheses
-            not is_type_ignore_comment_string(middle.prefix.strip())
+            not is_pragma_comment_string(middle.prefix.strip())
         ):
             first.value = ""
             last.value = ""

src/black/lines.py

@@ -29,7 +29,7 @@
     is_multiline_string,
     is_one_sequence_between,
     is_type_comment,
-    is_type_ignore_comment,
+    is_pragma_comment,
     is_with_or_async_with_stmt,
     replace_child,
     syms,
@@ -285,8 +285,7 @@ def contains_uncollapsable_type_comments(self) -> bool:
             for comment in comments:
                 if is_type_comment(comment):
                     if comment_seen or (
-                        not is_type_ignore_comment(comment)
-                        and leaf_id not in ignored_ids
+                        not is_pragma_comment(comment) and leaf_id not in ignored_ids
                     ):
                         return True
 
@@ -322,7 +321,7 @@ def contains_unsplittable_type_ignore(self) -> bool:
             # line.
             for node in self.leaves[-2:]:
                 for comment in self.comments.get(id(node), []):
-                    if is_type_ignore_comment(comment):
+                    if is_pragma_comment(comment):
                         return True
 
         return False

src/black/nodes.py

@@ -134,6 +134,8 @@
 BRACKETS: Final = OPENING_BRACKETS | CLOSING_BRACKETS
 ALWAYS_NO_SPACE: Final = CLOSING_BRACKETS | {token.COMMA, STANDALONE_COMMENT}
 
+PRAGMA_COMMENT_MARKER: Final = ("# type:", "# noqa", "# pylint:")
+
 RARROW = 55
 
 
@@ -848,17 +850,17 @@ def is_type_comment(leaf: Leaf) -> bool:
     return t in {token.COMMENT, STANDALONE_COMMENT} and v.startswith("# type:")
 
 
-def is_type_ignore_comment(leaf: Leaf) -> bool:
-    """Return True if the given leaf is a type comment with ignore annotation."""
+def is_pragma_comment(leaf: Leaf) -> bool:
+    """Return True if the given leaf is a pragma comment. Pragma comments cause lines to
+    be unsplittable, but mergeable."""
     t = leaf.type
     v = leaf.value
-    return t in {token.COMMENT, STANDALONE_COMMENT} and is_type_ignore_comment_string(v)
+    return t in {token.COMMENT, STANDALONE_COMMENT} and is_pragma_comment_string(v)
 
 
-def is_type_ignore_comment_string(value: str) -> bool:
-    """Return True if the given string match with type comment with
-    ignore annotation."""
-    return value.startswith("# type: ignore")
+def is_pragma_comment_string(value: str) -> bool:
+    """Return True if the given string matches a known pragma comment."""
+    return value.startswith(PRAGMA_COMMENT_MARKER)
 
 
 def wrap_in_parentheses(parent: Node, child: LN, *, visible: bool = True) -> None:

tests/data/cases/comments6.py

@@ -116,3 +116,38 @@ def func(
 )
 
 aaaaaaaaaaaaa, bbbbbbbbb = map(list, map(itertools.chain.from_iterable, zip(*items)))  # type: ignore[arg-type]
+
+
+def func(
+    a=some_list[0],  # type: int
+):  # type: () -> int
+    c = call(
+        0.0123,
+        0.0456,
+        0.0789,
+        0.0123,
+        0.0456,
+        0.0789,
+        0.0123,
+        0.0456,
+        0.0789,
+        a[-1],  # noqa
+    )
+
+    c = call(
+        "aaaaaaaa", "aaaaaaaa", "aaaaaaaa", "aaaaaaaa", "aaaaaaaa", "aaaaaaaa", "aaaaaaaa"  # noqa
+    )
+
+
+result = (  # aaa
+    "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+)
+
+AAAAAAAAAAAAA = [AAAAAAAAAAAAA] + SHARED_AAAAAAAAAAAAA + USER_AAAAAAAAAAAAA + AAAAAAAAAAAAA  # noqa
+
+call_to_some_function_asdf(
+    foo,
+    [AAAAAAAAAAAAAAAAAAAAAAA, AAAAAAAAAAAAAAAAAAAAAAA, AAAAAAAAAAAAAAAAAAAAAAA, BBBBBBBBBBBB],  # noqa
+)
+
+aaaaaaaaaaaaa, bbbbbbbbb = map(list, map(itertools.chain.from_iterable, zip(*items)))  # noqa: A000