Handle open-parenthesis comments on match case

crates/ruff_python_formatter/src/comments/placement.rs

@@ -210,6 +210,7 @@ fn handle_enclosed_comment<'a>(
             handle_leading_class_with_decorators_comment(comment, class_def)
         }
         AnyNodeRef::StmtImportFrom(import_from) => handle_import_from_comment(comment, import_from),
+        AnyNodeRef::MatchCase(match_case) => handle_match_case_comment(comment, match_case),
         AnyNodeRef::StmtWith(with_) => handle_with_comment(comment, with_),
         AnyNodeRef::ExprConstant(_) => {
             if let Some(AnyNodeRef::ExprFString(fstring)) = comment.enclosing_parent() {
@@ -1303,6 +1304,28 @@ fn handle_import_from_comment<'a>(
     }
 }
 
+/// Attach an enclosed end-of-line comment to a [`MatchCase`].
+///
+/// For example, given:
+/// ```python
+/// case (  # comment
+///    pattern
+/// ):
+///     ...
+/// ```
+///
+/// The comment will be attached to the [`MatchCase`] node as a dangling comment.
+fn handle_match_case_comment<'a>(
+    comment: DecoratedComment<'a>,
+    match_case: &'a MatchCase,
+) -> CommentPlacement<'a> {
+    if comment.line_position().is_end_of_line() && comment.start() < match_case.pattern.start() {
+        CommentPlacement::dangling(comment.enclosing_node(), comment)
+    } else {
+        CommentPlacement::Default(comment)
+    }
+}
+
 /// Attach an enclosed end-of-line comment to a [`ast::StmtWith`].
 ///
 /// For example, given:

crates/ruff_python_formatter/src/other/match_case.rs

@@ -1,9 +1,9 @@
-use ruff_formatter::{format_args, write, Buffer, FormatResult};
+use ruff_formatter::{write, Buffer, FormatResult};
 use ruff_python_ast::{MatchCase, Pattern, Ranged};
 use ruff_python_trivia::{SimpleTokenKind, SimpleTokenizer};
 use ruff_text_size::TextRange;
 
-use crate::comments::{leading_comments, SourceComment};
+use crate::comments::SourceComment;
 use crate::expression::parentheses::parenthesized;
 use crate::prelude::*;
 use crate::statement::clause::{clause_body, clause_header, ClauseHeader};
@@ -21,8 +21,13 @@ impl FormatNodeRule<MatchCase> for FormatMatchCase {
             body,
         } = item;
 
+        // Distinguish dangling comments that appear on the open parenthesis from those that
+        // appear on the trailing colon.
         let comments = f.context().comments().clone();
         let dangling_item_comments = comments.dangling(item);
+        let (open_parenthesis_comments, trailing_colon_comments) = dangling_item_comments.split_at(
+            dangling_item_comments.partition_point(|comment| comment.start() < pattern.start()),
+        );
 
         write!(
             f,
@@ -33,19 +38,12 @@ impl FormatNodeRule<MatchCase> for FormatMatchCase {
                     &format_with(|f| {
                         write!(f, [text("case"), space()])?;
 
-                        let leading_pattern_comments = comments.leading(pattern);
-                        if !leading_pattern_comments.is_empty() {
-                            parenthesized(
-                                "(",
-                                &format_args![
-                                    leading_comments(leading_pattern_comments),
-                                    pattern.format()
-                                ],
-                                ")",
-                            )
-                            .fmt(f)?;
-                        } else if is_match_case_pattern_parenthesized(item, pattern, f.context())? {
-                            parenthesized("(", &pattern.format(), ")").fmt(f)?;
+                        if !open_parenthesis_comments.is_empty()
+                            || is_match_case_pattern_parenthesized(item, pattern, f.context())?
+                        {
+                            parenthesized("(", &pattern.format(), ")")
+                                .with_dangling_comments(open_parenthesis_comments)
+                                .fmt(f)?;
                         } else {
                             pattern.format().fmt(f)?;
                         }
@@ -57,7 +55,7 @@ impl FormatNodeRule<MatchCase> for FormatMatchCase {
                         Ok(())
                     }),
                 ),
-                clause_body(body, dangling_item_comments),
+                clause_body(body, trailing_colon_comments),
             ]
         )
     }

crates/ruff_python_formatter/tests/snapshots/format@parentheses__opening_parentheses_comment_value.py.snap

@@ -222,8 +222,7 @@ match (  # d 2
     case d2:
         pass
 match d3:
-    case (
-        # d 3
+    case (  # d 3
         x
     ):
         pass

crates/ruff_python_formatter/tests/snapshots/format@statement__match.py.snap

@@ -354,8 +354,7 @@ match pattern_comments:
 
 
 match pattern_comments:
-    case (
-        # leading
+    case (  # leading
         only_leading
     ):
         pass