Format PatternMatchStar (#6653)

crates/ruff_python_formatter/resources/test/fixtures/ruff/statement/match.py

@@ -237,7 +237,6 @@ def foo():
     ]:
         pass
 
-
 match foo:
     case 1:
         y = 0
@@ -263,3 +262,40 @@ def foo():
         # comment
     ):
         y = 1
+
+match foo:
+    case [1, 2, *rest]:
+        pass
+    case [1, 2, *_]:
+        pass
+    case [*rest, 1, 2]:
+        pass
+    case [*_, 1, 2]:
+        pass
+    case [
+        1,
+        2,
+        *rest,
+    ]:
+        pass
+    case [1, 2, * # comment
+        rest]:
+        pass
+    case [1, 2, * # comment
+        _]:
+        pass
+    case [* # comment
+        rest, 1, 2]:
+        pass
+    case [* # comment
+        _, 1, 2]:
+        pass
+    case [* # end of line
+        # own line
+        _, 1, 2]:
+        pass
+    case [* # end of line
+        # own line
+        _, 1, 2]:
+        pass
+

crates/ruff_python_formatter/src/comments/placement.rs

@@ -206,6 +206,7 @@ fn handle_enclosed_comment<'a>(
         }
         AnyNodeRef::WithItem(_) => handle_with_item_comment(comment, locator),
         AnyNodeRef::PatternMatchAs(_) => handle_pattern_match_as_comment(comment, locator),
+        AnyNodeRef::PatternMatchStar(_) => handle_pattern_match_star_comment(comment),
         AnyNodeRef::StmtFunctionDef(_) => handle_leading_function_with_decorators_comment(comment),
         AnyNodeRef::StmtClassDef(class_def) => {
             handle_leading_class_with_decorators_comment(comment, class_def)
@@ -1187,6 +1188,20 @@ fn handle_pattern_match_as_comment<'a>(
     }
 }
 
+/// Handles dangling comments between the `*` token and identifier of a pattern match star:
+///
+/// ```python
+/// case [
+///   ...,
+///   *  # dangling end of line comment
+///   # dangling end of line comment
+///   rest,
+/// ]: ...
+/// ```
+fn handle_pattern_match_star_comment(comment: DecoratedComment) -> CommentPlacement {
+    CommentPlacement::dangling(comment.enclosing_node(), comment)
+}
+
 /// Handles comments around the `:=` token in a named expression (walrus operator).
 ///
 /// For example, here, `# 1` and `# 2` will be marked as dangling comments on the named expression,

crates/ruff_python_formatter/src/pattern/pattern_match_star.rs

@@ -1,19 +1,34 @@
-use ruff_formatter::{write, Buffer, FormatResult};
+use ruff_formatter::{prelude::text, write, Buffer, FormatResult};
 use ruff_python_ast::PatternMatchStar;
 
-use crate::{not_yet_implemented_custom_text, FormatNodeRule, PyFormatter};
+use crate::comments::{dangling_comments, SourceComment};
+use crate::AsFormat;
+use crate::{FormatNodeRule, PyFormatter};
 
 #[derive(Default)]
 pub struct FormatPatternMatchStar;
 
 impl FormatNodeRule<PatternMatchStar> for FormatPatternMatchStar {
     fn fmt_fields(&self, item: &PatternMatchStar, f: &mut PyFormatter) -> FormatResult<()> {
-        write!(
-            f,
-            [not_yet_implemented_custom_text(
-                "*NOT_YET_IMPLEMENTED_PatternMatchStar",
-                item
-            )]
-        )
+        let PatternMatchStar { name, .. } = item;
+
+        let comments = f.context().comments().clone();
+        let dangling = comments.dangling(item);
+
+        write!(f, [text("*"), dangling_comments(dangling)])?;
+
+        match name {
+            Some(name) => write!(f, [name.format()]),
+            None => write!(f, [text("_")]),
+        }
+    }
+
+    fn fmt_dangling_comments(
+        &self,
+        _dangling_comments: &[SourceComment],
+        _f: &mut PyFormatter,
+    ) -> FormatResult<()> {
+        // Handled by `fmt_fields`
+        Ok(())
     }
 }

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_complex.py.snap

@@ -179,8 +179,7 @@ match x:
          y = 0
  # case black_check_sequence_then_mapping
  match x:
--    case [*_]:
-+    case [*NOT_YET_IMPLEMENTED_PatternMatchStar]:
+     case [*_]:
          return "seq"
 -    case {}:
 +    case {"NOT_YET_IMPLEMENTED_PatternMatchMapping": _, 2: _}:
@@ -204,7 +203,7 @@ match x:
          x = True
  # case black_test_patma_154
  match x:
-@@ -54,15 +54,15 @@
+@@ -54,11 +54,11 @@
          y = 0
  # case black_test_patma_134
  match x:
@@ -219,12 +218,7 @@ match x:
          y = 2
  # case black_test_patma_185
  match Seq():
--    case [*_]:
-+    case [*NOT_YET_IMPLEMENTED_PatternMatchStar]:
-         y = 0
- # case black_test_patma_063
- match x:
-@@ -72,11 +72,11 @@
+@@ -72,7 +72,7 @@
          y = 1
  # case black_test_patma_248
  match x:
@@ -233,26 +227,7 @@ match x:
          y = bar
  # case black_test_patma_019
  match (0, 1, 2):
--    case [0, 1, *x, 2]:
-+    case [0, 1, *NOT_YET_IMPLEMENTED_PatternMatchStar, 2]:
-         y = 0
- # case black_test_patma_052
- match x:
-@@ -88,7 +88,7 @@
-         y = 2
- # case black_test_patma_191
- match w:
--    case [x, y, *_]:
-+    case [x, y, *NOT_YET_IMPLEMENTED_PatternMatchStar]:
-         z = 0
- # case black_test_patma_110
- match x:
-@@ -128,17 +128,17 @@
-         y = 0
- # case black_test_patma_189
- match w:
--    case [x, y, *rest]:
-+    case [x, y, *NOT_YET_IMPLEMENTED_PatternMatchStar]:
+@@ -132,13 +132,13 @@
          z = 0
  # case black_test_patma_042
  match x:
@@ -300,7 +275,7 @@ match x:
         y = 0
 # case black_check_sequence_then_mapping
 match x:
-    case [*NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case [*_]:
         return "seq"
     case {"NOT_YET_IMPLEMENTED_PatternMatchMapping": _, 2: _}:
         return "map"
@@ -338,7 +313,7 @@ match x:
         y = 2
 # case black_test_patma_185
 match Seq():
-    case [*NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case [*_]:
         y = 0
 # case black_test_patma_063
 match x:
@@ -352,7 +327,7 @@ match x:
         y = bar
 # case black_test_patma_019
 match (0, 1, 2):
-    case [0, 1, *NOT_YET_IMPLEMENTED_PatternMatchStar, 2]:
+    case [0, 1, *x, 2]:
         y = 0
 # case black_test_patma_052
 match x:
@@ -364,7 +339,7 @@ match x:
         y = 2
 # case black_test_patma_191
 match w:
-    case [x, y, *NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case [x, y, *_]:
         z = 0
 # case black_test_patma_110
 match x:
@@ -404,7 +379,7 @@ match x:
         y = 0
 # case black_test_patma_189
 match w:
-    case [x, y, *NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case [x, y, *rest]:
         z = 0
 # case black_test_patma_042
 match x:

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_extras.py.snap

@@ -161,7 +161,7 @@ match bar1:
              ...
          case another:
              ...
-@@ -32,23 +32,32 @@
+@@ -32,14 +32,23 @@
  match maybe, multiple:
      case perhaps, 5:
          pass
@@ -188,11 +188,9 @@ match bar1:
          pass
      case _:
          pass
- 
- 
+@@ -48,7 +57,7 @@
  match a, *b, c:
--    case [*_]:
-+    case [*NOT_YET_IMPLEMENTED_PatternMatchStar]:
+     case [*_]:
          assert "seq" == _
 -    case {}:
 +    case {"NOT_YET_IMPLEMENTED_PatternMatchMapping": _, 2: _}:
@@ -213,13 +211,7 @@ match bar1:
          pass
  
      case [a as match]:
-@@ -80,17 +84,14 @@
- 
- 
- match a, *b(), c:
--    case d, *f, g:
-+    case d, *NOT_YET_IMPLEMENTED_PatternMatchStar, g:
-         pass
+@@ -85,12 +89,9 @@
  
  
  match something:
@@ -234,17 +226,12 @@ match bar1:
          pass
  
  
-@@ -101,19 +102,22 @@
+@@ -101,19 +102,17 @@
      case 2 as b, 3 as c:
          pass
  
 -    case 4 as d, (5 as e), (6 | 7 as g), *h:
-+    case (
-+        4 as d,
-+        5 as e,
-+        NOT_YET_IMPLEMENTED_PatternMatchOf | (y) as g,
-+        *NOT_YET_IMPLEMENTED_PatternMatchStar,
-+    ):
++    case 4 as d, 5 as e, NOT_YET_IMPLEMENTED_PatternMatchOf | (y) as g, *h:
          pass
  
  
@@ -324,7 +311,7 @@ match (
 
 
 match a, *b, c:
-    case [*NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case [*_]:
         assert "seq" == _
     case {"NOT_YET_IMPLEMENTED_PatternMatchMapping": _, 2: _}:
         assert "map" == b
@@ -353,7 +340,7 @@ match match:
 
 
 match a, *b(), c:
-    case d, *NOT_YET_IMPLEMENTED_PatternMatchStar, g:
+    case d, *f, g:
         pass
 
 
@@ -371,12 +358,7 @@ match something:
     case 2 as b, 3 as c:
         pass
 
-    case (
-        4 as d,
-        5 as e,
-        NOT_YET_IMPLEMENTED_PatternMatchOf | (y) as g,
-        *NOT_YET_IMPLEMENTED_PatternMatchStar,
-    ):
+    case 4 as d, 5 as e, NOT_YET_IMPLEMENTED_PatternMatchOf | (y) as g, *h:
         pass
 
 

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_simple.py.snap

@@ -104,23 +104,7 @@ def where_is(point):
 ```diff
 --- Black
 +++ Ruff
-@@ -23,7 +23,7 @@
-     # The rest of your commands go here
- 
- match command.split():
--    case ["drop", *objects]:
-+    case ["drop", *NOT_YET_IMPLEMENTED_PatternMatchStar]:
-         for obj in objects:
-             character.drop(obj, current_room)
-     # The rest of your commands go here
-@@ -33,24 +33,24 @@
-         pass
-     case ["go", direction]:
-         print("Going:", direction)
--    case ["drop", *objects]:
-+    case ["drop", *NOT_YET_IMPLEMENTED_PatternMatchStar]:
-         print("Dropping: ", *objects)
-     case _:
+@@ -39,18 +39,18 @@
          print(f"Sorry, I couldn't understand {command!r}")
  
  match command.split():
@@ -217,7 +201,7 @@ match command.split():
     # The rest of your commands go here
 
 match command.split():
-    case ["drop", *NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case ["drop", *objects]:
         for obj in objects:
             character.drop(obj, current_room)
     # The rest of your commands go here
@@ -227,7 +211,7 @@ match command.split():
         pass
     case ["go", direction]:
         print("Going:", direction)
-    case ["drop", *NOT_YET_IMPLEMENTED_PatternMatchStar]:
+    case ["drop", *objects]:
         print("Dropping: ", *objects)
     case _:
         print(f"Sorry, I couldn't understand {command!r}")