Preserve tuple parentheses in case patterns (#18147)

Author: maxmynter

crates/ruff_python_formatter/resources/test/fixtures/ruff/pattern/pattern_maybe_parenthesize.py

@@ -288,5 +288,13 @@
     ]:
         pass
 
-
+match a, b:
+    case [], []:
+        ...
+    case [], _:
+        ...
+    case _, []:
+        ...
+    case _, _:
+        ...
 

crates/ruff_python_formatter/resources/test/fixtures/ruff/pattern_match_regression_brackets.py

@@ -0,0 +1,8 @@
+# Ruff in some cases added brackets around tuples in some cases; deviating from Black.
+# Ensure we don't revert already-applied formats with the fix.
+# See https://github.com/astral-sh/ruff/pull/18147
+match a, b:
+    case [[], []]:
+        ...
+    case [[], _]:
+        ...

crates/ruff_python_formatter/src/pattern/pattern_match_sequence.rs

@@ -79,9 +79,26 @@ pub(crate) enum SequenceType {
 
 impl SequenceType {
     pub(crate) fn from_pattern(pattern: &PatternMatchSequence, source: &str) -> SequenceType {
-        if source[pattern.range()].starts_with('[') {
+        let before_first_pattern = &source[TextRange::new(
+            pattern.start(),
+            pattern
+                .patterns
+                .first()
+                .map(Ranged::start)
+                .unwrap_or(pattern.end()),
+        )];
+        let after_last_patttern = &source[TextRange::new(
+            pattern.start(),
+            pattern
+                .patterns
+                .first()
+                .map(Ranged::end)
+                .unwrap_or(pattern.end()),
+        )];
+
+        if before_first_pattern.starts_with('[') && !after_last_patttern.ends_with(',') {
             SequenceType::List
-        } else if source[pattern.range()].starts_with('(') {
+        } else if before_first_pattern.starts_with('(') {
             // If the pattern is empty, it must be a parenthesized tuple with no members. (This
             // branch exists to differentiate between a tuple with and without its own parentheses,
             // but a tuple without its own parentheses must have at least one member.)

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

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_formatter/tests/fixtures.rs
 input_file: crates/ruff_python_formatter/resources/test/fixtures/black/cases/pattern_matching_trailing_comma.py
-snapshot_kind: text
 ---
 ## Input
 
@@ -27,7 +26,7 @@ match more := (than, one), indeed,:
 ```diff
 --- Black
 +++ Ruff
-@@ -8,13 +8,16 @@
+@@ -8,7 +8,10 @@
          pass
  
  
@@ -38,15 +37,7 @@ match more := (than, one), indeed,:
 +):
      case _, (5, 6):
          pass
--    case (
-+    case [
-         [[5], (6)],
-         [7],
--    ):
-+    ]:
-         pass
-     case _:
-         pass
+     case (
 ```
 
 ## Ruff Output
@@ -68,10 +59,10 @@ match (
 ):
     case _, (5, 6):
         pass
-    case [
+    case (
         [[5], (6)],
         [7],
-    ]:
+    ):
         pass
     case _:
         pass

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

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_formatter/tests/fixtures.rs
 input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/pattern/pattern_maybe_parenthesize.py
-snapshot_kind: text
 ---
 ## Input
 ```python
@@ -295,7 +294,15 @@ match x:
     ]:
         pass
 
-
+match a, b:
+    case [], []:
+        ...
+    case [], _:
+        ...
+    case _, []:
+        ...
+    case _, _:
+        ...
 
 ```
 
@@ -592,4 +599,14 @@ match x:
         ccccccccccccccccccccccccccccccccc,
     ]:
         pass
+
+match a, b:
+    case [], []:
+        ...
+    case [], _:
+        ...
+    case _, []:
+        ...
+    case _, _:
+        ...
 ```

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

@@ -0,0 +1,27 @@
+---
+source: crates/ruff_python_formatter/tests/fixtures.rs
+input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/pattern_match_regression_brackets.py
+---
+## Input
+```python
+# Ruff in some cases added brackets around tuples in some cases; deviating from Black.
+# Ensure we don't revert already-applied formats with the fix.
+# See https://github.com/astral-sh/ruff/pull/18147
+match a, b:
+    case [[], []]:
+        ...
+    case [[], _]:
+        ...
+```
+
+## Output
+```python
+# Ruff in some cases added brackets around tuples in some cases; deviating from Black.
+# Ensure we don't revert already-applied formats with the fix.
+# See https://github.com/astral-sh/ruff/pull/18147
+match a, b:
+    case [[], []]:
+        ...
+    case [[], _]:
+        ...
+```