Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ntBre merged 6 commits into from
Nov 3, 2025
+307 −4
Merged

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

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
a0d6d70
Avoid extra parentheses for long `match` patterns with `as` captures
ntBre Oct 31, 2025
bf99957
add failing expected tests from issue
ntBre Oct 31, 2025
7278067
pass tests
ntBre Oct 31, 2025
2ea7600
test that we wrap the as pattern too, if it's still too long
ntBre Oct 31, 2025
8b05703
preview gate
ntBre Oct 31, 2025
37d447a
add some comment tests
ntBre Nov 3, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
55 changes: 55 additions & 0 deletions crates/ruff_python_formatter/resources/test/fixtures/ruff/statement/match.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -613,3 +613,58 @@ def foo():
):
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
20 changes: 17 additions & 3 deletions crates/ruff_python_formatter/src/pattern/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -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::{
Expand All @@ -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;
Expand Down Expand Up @@ -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)
}
Expand Down Expand Up @@ -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,
Expand Down
9 changes: 9 additions & 0 deletions crates/ruff_python_formatter/src/preview.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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()
}
227 changes: 226 additions & 1 deletion crates/ruff_python_formatter/tests/snapshots/format@statement__match.py.snap
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
```