Merge branch 'main' into patch-1

.pre-commit-config.yaml

@@ -39,7 +39,7 @@ repos:
         exclude: ^src/blib2to3/
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.5.0
+    rev: v1.5.1
     hooks:
       - id: mypy
         exclude: ^docs/conf.py
@@ -53,7 +53,7 @@ repos:
           - hypothesis
 
   - repo: https://github.com/pre-commit/mirrors-prettier
-    rev: v3.0.1
+    rev: v3.0.3
     hooks:
       - id: prettier
         exclude: \.github/workflows/diff_shades\.yml

CHANGES.md

@@ -18,6 +18,7 @@
 
 - Long type hints are now wrapped in parentheses and properly indented when split across
   multiple lines (#3899)
+- Magic trailing commas are now respected in return types. (#3916)
 
 ### Configuration
 

docs/integrations/editors.md

@@ -399,9 +399,10 @@ close and reopen your File, _Black_ will be done with its job.
   server for Black. Formatting is much more responsive using this extension, **but the
   minimum supported version of Black is 22.3.0**.
 
-## SublimeText 3
+## SublimeText
 
-Use [sublack plugin](https://github.com/jgirardet/sublack).
+For SublimeText 3, use [sublack plugin](https://github.com/jgirardet/sublack). For
+higher versions, it is recommended to use [LSP](#python-lsp-server) as documented below.
 
 ## Python LSP Server
 

src/black/linegen.py

@@ -573,7 +573,7 @@ def transform_line(
             transformers = [string_merge, string_paren_strip]
         else:
             transformers = []
-    elif line.is_def:
+    elif line.is_def and not should_split_funcdef_with_rhs(line, mode):
         transformers = [left_hand_split]
     else:
 
@@ -652,6 +652,40 @@ def _rhs(
         yield line
 
 
+def should_split_funcdef_with_rhs(line: Line, mode: Mode) -> bool:
+    """If a funcdef has a magic trailing comma in the return type, then we should first
+    split the line with rhs to respect the comma.
+    """
+    if Preview.respect_magic_trailing_comma_in_return_type not in mode:
+        return False
+
+    return_type_leaves: List[Leaf] = []
+    in_return_type = False
+
+    for leaf in line.leaves:
+        if leaf.type == token.COLON:
+            in_return_type = False
+        if in_return_type:
+            return_type_leaves.append(leaf)
+        if leaf.type == token.RARROW:
+            in_return_type = True
+
+    # using `bracket_split_build_line` will mess with whitespace, so we duplicate a
+    # couple lines from it.
+    result = Line(mode=line.mode, depth=line.depth)
+    leaves_to_track = get_leaves_inside_matching_brackets(return_type_leaves)
+    for leaf in return_type_leaves:
+        result.append(
+            leaf,
+            preformatted=True,
+            track_bracket=id(leaf) in leaves_to_track,
+        )
+
+    # we could also return true if the line is too long, and the return type is longer
+    # than the param list. Or if `should_split_rhs` returns True.
+    return result.magic_trailing_comma is not None
+
+
 class _BracketSplitComponent(Enum):
     head = auto()
     body = auto()

src/black/mode.py

@@ -181,6 +181,7 @@ class Preview(Enum):
     string_processing = auto()
     parenthesize_conditional_expressions = auto()
     parenthesize_long_type_hints = auto()
+    respect_magic_trailing_comma_in_return_type = auto()
     skip_magic_trailing_comma_in_subscript = auto()
     wrap_long_dict_values_in_parens = auto()
     wrap_multiple_context_managers_in_parens = auto()

tests/data/preview/return_annotation_brackets_string.py

@@ -2,6 +2,10 @@
 def frobnicate() -> "ThisIsTrulyUnreasonablyExtremelyLongClassName | list[ThisIsTrulyUnreasonablyExtremelyLongClassName]":
     pass
 
+# splitting the string breaks if there's any parameters
+def frobnicate(a) -> "ThisIsTrulyUnreasonablyExtremelyLongClassName | list[ThisIsTrulyUnreasonablyExtremelyLongClassName]":
+    pass
+
 # output
 
 # Long string example
@@ -10,3 +14,10 @@ def frobnicate() -> (
     " list[ThisIsTrulyUnreasonablyExtremelyLongClassName]"
 ):
     pass
+
+
+# splitting the string breaks if there's any parameters
+def frobnicate(
+    a,
+) -> "ThisIsTrulyUnreasonablyExtremelyLongClassName | list[ThisIsTrulyUnreasonablyExtremelyLongClassName]":
+    pass