Avoid extra parentheses for long `match` patterns with `as` captures (#21176)

Summary
--

This PR fixes #17796 by taking the approach mentioned in
https://github.com/astral-sh/ruff/issues/17796#issuecomment-2847943862
of simply recursing into the `MatchAs` patterns when checking if we need
parentheses. This allows us to reuse the parentheses in the inner
pattern before also breaking the `MatchAs` pattern itself:

```diff
 match class_pattern:
     case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:
         pass
-    case (
-        Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture
-    ):
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as capture:
         pass
-    case (
-        Class(
-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
-        ) as capture
-    ):
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as capture:
         pass
     case (
         Class(
@@ -685,13 +683,11 @@
 match sequence_pattern_brackets:
     case [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture:
         pass
-    case (
-        [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture
-    ):
+    case [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ] as capture:
         pass
-    case (
-        [
-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
-        ] as capture
-    ):
+    case [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ] as capture:
         pass
```

I haven't really resolved the question of whether or not it's okay
always to recurse, but I'm hoping the ecosystem check on this PR might
shed some light on that.

Test Plan
--

New tests based on the issue and then reviewing the ecosystem check here

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

@@ -613,3 +613,58 @@ match guard_comments:
     ):
         pass
 
+
+# regression tests from https://github.com/astral-sh/ruff/issues/17796
+match class_pattern:
+    case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:
+        pass
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as capture:
+        pass
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as capture:
+        pass
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture:
+        pass
+
+match sequence_pattern_brackets:
+    case [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture:
+        pass
+    case [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ] as capture:
+        pass
+    case [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ] as capture:
+        pass
+
+
+match class_pattern:
+    # 1
+    case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:  # 2
+        # 3
+        pass # 4
+    # 5
+    case Class( # 6
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 7
+    ) as capture: # 8
+        pass
+    case Class( # 9
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 10
+    ) as capture: # 11
+        pass
+    case Class( # 12
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 13
+    ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture: # 14
+        pass
+    case Class( # 0
+            # 1
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 2
+            # 3
+    ) as capture:
+        pass

crates/ruff_python_formatter/src/pattern/mod.rs

@@ -1,5 +1,5 @@
 use ruff_formatter::{FormatOwnedWithRule, FormatRefWithRule, FormatRule, FormatRuleWithOptions};
-use ruff_python_ast::{AnyNodeRef, Expr};
+use ruff_python_ast::{AnyNodeRef, Expr, PatternMatchAs};
 use ruff_python_ast::{MatchCase, Pattern};
 use ruff_python_trivia::CommentRanges;
 use ruff_python_trivia::{
@@ -14,6 +14,7 @@ use crate::expression::parentheses::{
     NeedsParentheses, OptionalParentheses, Parentheses, optional_parentheses, parenthesized,
 };
 use crate::prelude::*;
+use crate::preview::is_avoid_parens_for_long_as_captures_enabled;
 
 pub(crate) mod pattern_arguments;
 pub(crate) mod pattern_keyword;
@@ -242,8 +243,14 @@ pub(crate) fn can_pattern_omit_optional_parentheses(
                 Pattern::MatchValue(_)
                 | Pattern::MatchSingleton(_)
                 | Pattern::MatchStar(_)
-                | Pattern::MatchAs(_)
                 | Pattern::MatchOr(_) => false,
+                Pattern::MatchAs(PatternMatchAs { pattern, .. }) => match pattern {
+                    Some(pattern) => {
+                        is_avoid_parens_for_long_as_captures_enabled(context)
+                            && has_parentheses_and_is_non_empty(pattern, context)
+                    }
+                    None => false,
+                },
                 Pattern::MatchSequence(sequence) => {
                     !sequence.patterns.is_empty() || context.comments().has_dangling(pattern)
                 }
@@ -318,7 +325,14 @@ impl<'a> CanOmitOptionalParenthesesVisitor<'a> {
                 // The pattern doesn't start with a parentheses pattern, but with the class's identifier.
                 self.first.set_if_none(First::Token);
             }
-            Pattern::MatchStar(_) | Pattern::MatchSingleton(_) | Pattern::MatchAs(_) => {}
+            Pattern::MatchAs(PatternMatchAs { pattern, .. }) => {
+                if let Some(pattern) = pattern
+                    && is_avoid_parens_for_long_as_captures_enabled(context)
+                {
+                    self.visit_sub_pattern(pattern, context);
+                }
+            }
+            Pattern::MatchStar(_) | Pattern::MatchSingleton(_) => {}
             Pattern::MatchOr(or_pattern) => {
                 self.update_max_precedence(
                     OperatorPrecedence::Or,

crates/ruff_python_formatter/src/preview.rs

@@ -43,3 +43,12 @@ pub(crate) const fn is_remove_parens_around_except_types_enabled(
 pub(crate) const fn is_allow_newline_after_block_open_enabled(context: &PyFormatContext) -> bool {
     context.is_preview()
 }
+
+/// Returns `true` if the
+/// [`avoid_parens_for_long_as_captures`](https://github.com/astral-sh/ruff/pull/21176) preview
+/// style is enabled.
+pub(crate) const fn is_avoid_parens_for_long_as_captures_enabled(
+    context: &PyFormatContext,
+) -> bool {
+    context.is_preview()
+}

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

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_formatter/tests/fixtures.rs
 input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/statement/match.py
-snapshot_kind: text
 ---
 ## Input
 ```python
@@ -620,6 +619,61 @@ match guard_comments:
     ):
         pass
 
+
+# regression tests from https://github.com/astral-sh/ruff/issues/17796
+match class_pattern:
+    case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:
+        pass
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as capture:
+        pass
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as capture:
+        pass
+    case Class(
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture:
+        pass
+
+match sequence_pattern_brackets:
+    case [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture:
+        pass
+    case [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ] as capture:
+        pass
+    case [
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+    ] as capture:
+        pass
+
+
+match class_pattern:
+    # 1
+    case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:  # 2
+        # 3
+        pass # 4
+    # 5
+    case Class( # 6
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 7
+    ) as capture: # 8
+        pass
+    case Class( # 9
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 10
+    ) as capture: # 11
+        pass
+    case Class( # 12
+        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 13
+    ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture: # 14
+        pass
+    case Class( # 0
+            # 1
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx # 2
+            # 3
+    ) as capture:
+        pass
 ```
 
 ## Output
@@ -1285,4 +1339,175 @@ match guard_comments:
         # trailing own line comment
     ):
         pass
+
+
+# regression tests from https://github.com/astral-sh/ruff/issues/17796
+match class_pattern:
+    case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:
+        pass
+    case (
+        Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture
+    ):
+        pass
+    case (
+        Class(
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+        ) as capture
+    ):
+        pass
+    case (
+        Class(
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+        ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture
+    ):
+        pass
+
+match sequence_pattern_brackets:
+    case [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture:
+        pass
+    case (
+        [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture
+    ):
+        pass
+    case (
+        [
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+        ] as capture
+    ):
+        pass
+
+
+match class_pattern:
+    # 1
+    case (
+        Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture
+    ):  # 2
+        # 3
+        pass  # 4
+    # 5
+    case (
+        Class(  # 6
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 7
+        ) as capture
+    ):  # 8
+        pass
+    case (
+        Class(  # 9
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 10
+        ) as capture
+    ):  # 11
+        pass
+    case (
+        Class(  # 12
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 13
+        ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture
+    ):  # 14
+        pass
+    case (
+        Class(  # 0
+            # 1
+            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 2
+            # 3
+        ) as capture
+    ):
+        pass
+```
+
+
+## Preview changes
+```diff
+--- Stable
++++ Preview
+@@ -665,15 +665,13 @@
+ match class_pattern:
+     case Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture:
+         pass
+-    case (
+-        Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture
+-    ):
++    case Class(
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
++    ) as capture:
+         pass
+-    case (
+-        Class(
+-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+-        ) as capture
+-    ):
++    case Class(
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
++    ) as capture:
+         pass
+     case (
+         Class(
+@@ -685,37 +683,31 @@
+ match sequence_pattern_brackets:
+     case [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture:
+         pass
+-    case (
+-        [xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] as capture
+-    ):
++    case [
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
++    ] as capture:
+         pass
+-    case (
+-        [
+-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+-        ] as capture
+-    ):
++    case [
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
++    ] as capture:
+         pass
+ 
+ 
+ match class_pattern:
+     # 1
+-    case (
+-        Class(xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) as capture
+-    ):  # 2
++    case Class(
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
++    ) as capture:  # 2
+         # 3
+         pass  # 4
+     # 5
+-    case (
+-        Class(  # 6
+-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 7
+-        ) as capture
+-    ):  # 8
++    case Class(  # 6
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 7
++    ) as capture:  # 8
+         pass
+-    case (
+-        Class(  # 9
+-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 10
+-        ) as capture
+-    ):  # 11
++    case Class(  # 9
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 10
++    ) as capture:  # 11
+         pass
+     case (
+         Class(  # 12
+@@ -723,11 +715,9 @@
+         ) as really_really_really_really_really_really_really_really_really_really_really_really_long_capture
+     ):  # 14
+         pass
+-    case (
+-        Class(  # 0
+-            # 1
+-            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 2
+-            # 3
+-        ) as capture
+-    ):
++    case Class(  # 0
++        # 1
++        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  # 2
++        # 3
++    ) as capture:
+         pass
 ```