Parenthesize match..case if guards (#13513)

Author: MichaReiser

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

@@ -588,3 +588,28 @@ def foo():
 match x:
     case Child(aaaaaaaaa, bbbbbbbbbbbbbbb, cccccc), Doc(aaaaa, bbbbbbbbbb, ddddddddddddd):
         pass
+
+
+match guard_comments:
+    case "abcd" if (  # trailing open parentheses comment
+        aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2
+    ):
+        pass
+
+    case "bcdef" if (
+        aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2 # trailing end of line comment
+    ):  # comment
+        pass
+
+    case "efgh" if (
+        # leading own line comment
+        aaaaaahhhhhh == 1
+    ):
+        pass
+
+    case "hijk" if (
+        aaaaaaaaa == 1
+        # trailing own line comment
+    ):
+        pass
+

crates/ruff_python_formatter/src/expression/parentheses.rs

@@ -59,6 +59,10 @@ pub(crate) enum Parenthesize {
     /// Same as [`Self::IfBreaks`] except that it uses [`parenthesize_if_expands`] for expressions
     /// with the layout [`NeedsParentheses::BestFit`] which is used by non-splittable
     /// expressions like literals, name, and strings.
+    ///
+    /// Use this layout over `IfBreaks` when there's a sequence of `maybe_parenthesize_expression`
+    /// in a single logical-line and you want to break from right-to-left. Use `IfBreaks` for the
+    /// first expression and `IfBreaksParenthesized` for the rest.
     IfBreaksParenthesized,
 
     /// Same as [`Self::IfBreaksParenthesized`] but uses [`parenthesize_if_expands`] for nested

crates/ruff_python_formatter/src/other/match_case.rs

@@ -3,7 +3,10 @@ use ruff_python_ast::AstNode;
 use ruff_python_ast::MatchCase;
 
 use crate::builders::parenthesize_if_expands;
-use crate::expression::parentheses::{NeedsParentheses, OptionalParentheses, Parentheses};
+use crate::expression::maybe_parenthesize_expression;
+use crate::expression::parentheses::{
+    NeedsParentheses, OptionalParentheses, Parentheses, Parenthesize,
+};
 use crate::pattern::maybe_parenthesize_pattern;
 use crate::prelude::*;
 use crate::preview::is_match_case_parentheses_enabled;
@@ -62,20 +65,27 @@ impl FormatNodeRule<MatchCase> for FormatMatchCase {
             }
         });
 
+        let format_guard = guard.as_deref().map(|guard| {
+            format_with(|f| {
+                write!(f, [space(), token("if"), space()])?;
+
+                if is_match_case_parentheses_enabled(f.context()) {
+                    maybe_parenthesize_expression(guard, item, Parenthesize::IfBreaksParenthesized)
+                        .fmt(f)
+                } else {
+                    guard.format().fmt(f)
+                }
+            })
+        });
+
         write!(
             f,
             [
                 clause_header(
                     ClauseHeader::MatchCase(item),
                     dangling_item_comments,
                     &format_with(|f| {
-                        write!(f, [token("case"), space(), format_pattern])?;
-
-                        if let Some(guard) = guard {
-                            write!(f, [space(), token("if"), space(), guard.format()])?;
-                        }
-
-                        Ok(())
+                        write!(f, [token("case"), space(), format_pattern, format_guard])
                     }),
                 ),
                 clause_body(

crates/ruff_python_formatter/src/preview.rs

@@ -39,6 +39,8 @@ pub(crate) fn is_empty_parameters_no_unnecessary_parentheses_around_return_value
 
 /// See [#6933](https://github.com/astral-sh/ruff/issues/6933).
 /// This style also covers the black preview styles `remove_redundant_guard_parens` and `parens_for_long_if_clauses_in_case_block `.
+/// WARNING: This preview style depends on `is_empty_parameters_no_unnecessary_parentheses_around_return_value_enabled`
+/// because it relies on the new semantic of `IfBreaksParenthesized`.
 pub(crate) fn is_match_case_parentheses_enabled(context: &PyFormatContext) -> bool {
     context.is_preview()
 }

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

@@ -44,36 +44,9 @@ match x:
 ```diff
 --- Black
 +++ Ruff
-@@ -3,34 +3,36 @@
+@@ -21,11 +21,17 @@
          pass
- 
- match smth:
--    case "test" if (
--        "any long condition" != "another long condition" and "this is a long condition"
--    ):
-+    case "test" if "any long condition" != "another long condition" and "this is a long condition":
-         pass
--    case test if (
--        "any long condition" != "another long condition"
--        and "this is a looooong condition"
--    ):
-+    case (
-+        test
-+    ) if "any long condition" != "another long condition" and "this is a looooong condition":
-         pass
--    case test if (
--        "any long condition" != "another long condition"
--        and "this is a looooong condition"
--    ):  # some additional comments
-+    case (
-+        test
-+    ) if "any long condition" != "another long condition" and "this is a looooong condition":  # some additional comments
-         pass
--    case test if True:  # some comment
-+    case test if (True):  # some comment
-         pass
--    case test if False:  # some comment
-+    case test if (False):  # some comment
+     case test if False:  # some comment
          pass
 -    case test if True:  # some comment
 +    case test if (
@@ -92,12 +65,6 @@ match x:
          pass  # some comment
  
  # case black_test_patma_052 (originally in the pattern_matching_complex test case)
- match x:
-     case [1, 0] if x := x[:0]:
-         y = 1
--    case [1, 0] if x := x[:0]:
-+    case [1, 0] if (x := x[:0]):
-         y = 1
 ```
 
 ## Ruff Output
@@ -108,19 +75,23 @@ match match:
         pass
 
 match smth:
-    case "test" if "any long condition" != "another long condition" and "this is a long condition":
+    case "test" if (
+        "any long condition" != "another long condition" and "this is a long condition"
+    ):
         pass
-    case (
-        test
-    ) if "any long condition" != "another long condition" and "this is a looooong condition":
+    case test if (
+        "any long condition" != "another long condition"
+        and "this is a looooong condition"
+    ):
         pass
-    case (
-        test
-    ) if "any long condition" != "another long condition" and "this is a looooong condition":  # some additional comments
+    case test if (
+        "any long condition" != "another long condition"
+        and "this is a looooong condition"
+    ):  # some additional comments
         pass
-    case test if (True):  # some comment
+    case test if True:  # some comment
         pass
-    case test if (False):  # some comment
+    case test if False:  # some comment
         pass
     case test if (
         True  # some comment
@@ -139,7 +110,7 @@ match smth:
 match x:
     case [1, 0] if x := x[:0]:
         y = 1
-    case [1, 0] if (x := x[:0]):
+    case [1, 0] if x := x[:0]:
         y = 1
 ```
 

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

@@ -69,20 +69,7 @@ match 1:
 ```diff
 --- Black
 +++ Ruff
-@@ -1,10 +1,10 @@
- match 1:
--    case _ if True:
-+    case _ if (True):
-         pass
- 
- 
- match 1:
--    case _ if True:
-+    case _ if (True):
-         pass
- 
- 
-@@ -25,27 +25,33 @@
+@@ -25,12 +25,16 @@
  
  
  match 1:
@@ -101,18 +88,7 @@ match 1:
          pass
  
  
- match 1:
--    case _ if True:  # this is a comment
-+    case _ if (True):  # this is a comment
-         pass
- 
- 
- match 1:
--    case _ if True:  # comment over the line limit unless parens are removed x
-+    case _ if (
-+        True
-+    ):  # comment over the line limit unless parens are removed x
-         pass
+@@ -45,7 +49,7 @@
  
  
  match 1:
@@ -129,12 +105,12 @@ match 1:
 
 ```python
 match 1:
-    case _ if (True):
+    case _ if True:
         pass
 
 
 match 1:
-    case _ if (True):
+    case _ if True:
         pass
 
 
@@ -169,14 +145,12 @@ match 1:
 
 
 match 1:
-    case _ if (True):  # this is a comment
+    case _ if True:  # this is a comment
         pass
 
 
 match 1:
-    case _ if (
-        True
-    ):  # comment over the line limit unless parens are removed x
+    case _ if True:  # comment over the line limit unless parens are removed x
         pass
 
 

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

@@ -594,6 +594,31 @@ match n % 3, n % 5:
 match x:
     case Child(aaaaaaaaa, bbbbbbbbbbbbbbb, cccccc), Doc(aaaaa, bbbbbbbbbb, ddddddddddddd):
         pass
+
+
+match guard_comments:
+    case "abcd" if (  # trailing open parentheses comment
+        aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2
+    ):
+        pass
+
+    case "bcdef" if (
+        aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2 # trailing end of line comment
+    ):  # comment
+        pass
+
+    case "efgh" if (
+        # leading own line comment
+        aaaaaahhhhhh == 1
+    ):
+        pass
+
+    case "hijk" if (
+        aaaaaaaaa == 1
+        # trailing own line comment
+    ):
+        pass
+
 ```
 
 ## Output
@@ -1232,24 +1257,80 @@ match x:
         aaaaa, bbbbbbbbbb, ddddddddddddd
     ):
         pass
+
+
+match guard_comments:
+    case "abcd" if (  # trailing open parentheses comment
+        aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2
+    ):
+        pass
+
+    case "bcdef" if (
+        aaaaaaaaahhhhhhhh == 1
+        and bbbbbbaaaaaaaaaaa == 2  # trailing end of line comment
+    ):  # comment
+        pass
+
+    case "efgh" if (
+        # leading own line comment
+        aaaaaahhhhhh == 1
+    ):
+        pass
+
+    case "hijk" if (
+        aaaaaaaaa == 1
+        # trailing own line comment
+    ):
+        pass
 ```
 
 
 ## Preview changes
 ```diff
 --- Stable
 +++ Preview
+@@ -69,7 +69,7 @@
+     case "case comment with newlines" if foo == 2:  # second
+         pass
+ 
+-    case "one", "newline" if (foo := 1):  # third
++    case "one", "newline" if foo := 1:  # third
+         pass
+ 
+     case "two newlines":
 @@ -82,7 +82,9 @@
  
  
  match long_lines:
 -    case "this is a long line for if condition" if aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2:  # comment
-+    case (
-+        "this is a long line for if condition"
-+    ) if aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2:  # comment
++    case "this is a long line for if condition" if (
++        aaaaaaaaahhhhhhhh == 1 and bbbbbbaaaaaaaaaaa == 2
++    ):  # comment
          pass
  
      case "this is a long line for if condition with parentheses" if (
+@@ -93,7 +95,7 @@
+     case "named expressions aren't special" if foo := 1:
+         pass
+ 
+-    case "named expressions aren't that special" if (foo := 1):
++    case "named expressions aren't that special" if foo := 1:
+         pass
+ 
+     case "but with already broken long lines" if (
+@@ -101,9 +103,9 @@
+     ):  # another comment
+         pass
+ 
+-    case {
+-        "long_long_long_key": str(long_long_long_key)
+-    } if value := "long long long long long long long long long long long value":
++    case {"long_long_long_key": str(long_long_long_key)} if (
++        value := "long long long long long long long long long long long value"
++    ):
+         pass
+ 
+ 
 @@ -198,7 +200,9 @@
          # trailing own 2
      ):