Format PatternMatchAs (#6652)

## Summary

Add formatting for `PatternMatchAs`.

This closes #6641.

## Test Plan

Add tests for comments.

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

@@ -143,6 +143,35 @@ match pattern_comments:
         pass
 
 
+match pattern_comments:
+    case (
+        # 1
+        pattern  # 2
+        # 3
+        as  # 4
+        # 5
+        name  # 6
+        # 7
+    ):
+        pass
+
+
+match pattern_comments:
+    case (
+        pattern
+        # 1
+		as # 2
+        # 3
+		name #4
+        # 5
+    ):
+        pass
+
+
+match x:
+    case (a as b) as c:
+        pass
+
 match pattern_singleton:
     case (
         # leading 1

crates/ruff_python_formatter/src/pattern/pattern_match_as.rs

@@ -1,19 +1,42 @@
 use ruff_formatter::{write, Buffer, FormatResult};
-use ruff_python_ast::PatternMatchAs;
+use ruff_python_ast::{Pattern, PatternMatchAs};
 
-use crate::{not_yet_implemented_custom_text, FormatNodeRule, PyFormatter};
+use crate::expression::parentheses::parenthesized;
+use crate::prelude::*;
+use crate::{FormatNodeRule, PyFormatter};
 
 #[derive(Default)]
 pub struct FormatPatternMatchAs;
 
 impl FormatNodeRule<PatternMatchAs> for FormatPatternMatchAs {
     fn fmt_fields(&self, item: &PatternMatchAs, f: &mut PyFormatter) -> FormatResult<()> {
-        write!(
+        let PatternMatchAs {
-            f,
+            range: _,
-            [not_yet_implemented_custom_text(
+            pattern,
-                "x as NOT_YET_IMPLEMENTED_PatternMatchAs",
+            name,
-                item
+        } = item;
-            )]
+
-        )
+        if let Some(name) = name {
+            if let Some(pattern) = pattern {
+                // Parenthesize nested `PatternMatchAs` like `(a as b) as c`.
+                if matches!(
+                    pattern.as_ref(),
+                    Pattern::MatchAs(PatternMatchAs {
+                        pattern: Some(_),
+                        ..
+                    })
+                ) {
+                    parenthesized("(", &pattern.format(), ")").fmt(f)?;
+                } else {
+                    pattern.format().fmt(f)?;
+                }
+
+                write!(f, [space(), text("as"), space()])?;
+            }
+            name.format().fmt(f)
+        } else {
+            debug_assert!(pattern.is_none());
+            text("_").fmt(f)
+        }
     }
 }

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_complex.py.snap

@@ -301,7 +301,7 @@ match x:
          y = 0
  # case black_test_patma_233
  match x:
-@@ -116,29 +116,29 @@
+@@ -116,11 +116,11 @@
          y = 0
  # case black_test_patma_078
  match x:
@@ -316,8 +316,7 @@ match x:
          y = 2
  # case black_test_patma_156
  match x:
--    case z:
+@@ -128,17 +128,17 @@
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          y = 0
  # case black_test_patma_189
  match w:
@@ -471,7 +470,7 @@ match x:
         y = 2
 # case black_test_patma_156
 match x:
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case z:
         y = 0
 # case black_test_patma_189
 match w:

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_extras.py.snap

@@ -149,25 +149,23 @@ match bar1:
          print(x, y)
  
  
-@@ -15,40 +15,43 @@
+@@ -15,7 +15,7 @@
  case: int = re.match(something)
  
  match re.match(case):
 -    case type("match", match):
 +    case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
          pass
--    case match:
+     case match:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          pass
- 
+@@ -23,32 +23,35 @@
  
  def func(match: case, case: match) -> case:
      match Something():
 -        case func(match, case):
 +        case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
              ...
--        case another:
+         case another:
-+        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
              ...
  
  
@@ -191,8 +189,7 @@ match bar1:
 -    case [[5], (6)], [7],:
 +    case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
          pass
--    case _:
+     case _:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          pass
  
  
@@ -205,7 +202,7 @@ match bar1:
          assert "map" == b
  
  
-@@ -59,61 +62,51 @@
+@@ -59,15 +62,10 @@
      ),
      case,
  ):
@@ -222,15 +219,8 @@ match bar1:
 +    case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
          pass
  
--    case case:
+     case case:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+@@ -80,40 +78,35 @@
-         pass
- 
- 
- match match:
--    case case:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
-         pass
  
  
  match a, *b(), c:
@@ -253,7 +243,7 @@ match bar1:
  
  match something:
 -    case 1 as a:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
++    case "NOT_YET_IMPLEMENTED_PatternMatchValue" as a:
          pass
  
 -    case 2 as b, 3 as c:
@@ -269,8 +259,7 @@ match bar1:
 -    case Foo(aa=Callable() as aa, bb=int()):
 +    case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
          print(bar1.aa, bar1.bb)
--    case _:
+     case _:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          print("no match", "\n")
  
  
@@ -304,7 +293,7 @@ case: int = re.match(something)
 match re.match(case):
     case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
         pass
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case match:
         pass
 
 
@@ -312,7 +301,7 @@ def func(match: case, case: match) -> case:
     match Something():
         case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
             ...
-        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+        case another:
             ...
 
 
@@ -331,7 +320,7 @@ match (
         pass
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
         pass
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case _:
         pass
 
 
@@ -355,12 +344,12 @@ match match(
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
         pass
 
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case case:
         pass
 
 
 match match:
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case case:
         pass
 
 
@@ -377,7 +366,7 @@ match something:
 
 
 match something:
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case "NOT_YET_IMPLEMENTED_PatternMatchValue" as a:
         pass
 
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
@@ -390,7 +379,7 @@ match something:
 match bar1:
     case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
         print(bar1.aa, bar1.bb)
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case _:
         print("no match", "\n")
 
 

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_generic.py.snap

@@ -119,18 +119,6 @@ with match() as match:
 ```diff
 --- Black
 +++ Ruff
-@@ -24,9 +24,9 @@
-         ]
- 
-     match match:
--        case case:
-+        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
-             match match:
--                case case:
-+                case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
-                     pass
- 
-     if all(version.is_python2() for version in target_versions):
 @@ -46,7 +46,7 @@
      def test_patma_139(self):
          x = False
@@ -188,9 +176,9 @@ def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
         ]
 
     match match:
-        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+        case case:
             match match:
-                case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+                case case:
                     pass
 
     if all(version.is_python2() for version in target_versions):

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_simple.py.snap

@@ -153,8 +153,7 @@ def where_is(point):
 -    case ["drop", *objects]:
 +    case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
          print("Dropping: ", *objects)
--    case _:
+     case _:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          print(f"Sorry, I couldn't understand {command!r}")
  
  match command.split():
@@ -197,8 +196,7 @@ def where_is(point):
 -    case KeyPress():
 +    case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
          pass  # Ignore other keystrokes
--    case other_event:
+     case other_event:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          raise ValueError(f"Unrecognized event: {other_event}")
  
  match event.get():
@@ -224,8 +222,7 @@ def where_is(point):
 -        case Point():
 +        case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
              print("Somewhere else")
--        case _:
+         case _:
-+        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
              print("Not a point")
 ```
 
@@ -269,7 +266,7 @@ match command.split():
         print("Going:", direction)
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
         print("Dropping: ", *objects)
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case _:
         print(f"Sorry, I couldn't understand {command!r}")
 
 match command.split():
@@ -302,7 +299,7 @@ match event.get():
         game.go_north()
     case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
         pass  # Ignore other keystrokes
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case other_event:
         raise ValueError(f"Unrecognized event: {other_event}")
 
 match event.get():
@@ -322,7 +319,7 @@ def where_is(point):
             print(f"X={x}")
         case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
             print("Somewhere else")
-        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+        case _:
             print("Not a point")
 ```
 

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_310__pattern_matching_style.py.snap

@@ -81,8 +81,7 @@ match match(
 -    ):
 +    case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
          print(2)
--    case a:
+     case a:
-+    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
          pass
  
 -match(arg)  # comment
@@ -127,7 +126,7 @@ match something:
         print(1)
     case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
         print(2)
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case a:
         pass
 
 match(

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

@@ -89,7 +89,7 @@ def http_error(status):
             return "Not found"
         case "NOT_YET_IMPLEMENTED_PatternMatchValue":
             return "I'm a teapot"
-        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+        case _:
             return "Something's wrong with the internet"
 
 
@@ -103,7 +103,7 @@ match point:
         print(f"X={x}")
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
         print(f"X={x}, Y={y}")
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case _:
         raise ValueError("Not a point")
 
 
@@ -122,7 +122,7 @@ def location(point):
             print(f"X={x} and the point is on the x-axis.")
         case NOT_YET_IMPLEMENTED_PatternMatchClass(0, 0):
             print("The point is located somewhere else on the plane.")
-        case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+        case _:
             print("Not a point")
 
 
@@ -137,7 +137,7 @@ match points:
         print(f"A single point {x}, {y} is in the list.")
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:
         print(f"Two points on the Y axis at {y1}, {y2} are in the list.")
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case _:
         print("Something else is found in the list.")
 
 

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

@@ -139,7 +139,7 @@ with (  # d 1
     pass
 match (  # d 2
 ):
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case d2:
         pass
 match d3:
     case [NOT_YET_IMPLEMENTED_PatternMatchSequence, 2]:

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

@@ -219,12 +219,12 @@ with (  # d 1
 match (  # d 2
     x
 ):
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case d2:
         pass
 match d3:
     case (
         # d 3
-        x as NOT_YET_IMPLEMENTED_PatternMatchAs
+        x
     ):
         pass
 while (  # d 4

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

@@ -149,6 +149,35 @@ match pattern_comments:
         pass
 
 
+match pattern_comments:
+    case (
+        # 1
+        pattern  # 2
+        # 3
+        as  # 4
+        # 5
+        name  # 6
+        # 7
+    ):
+        pass
+
+
+match pattern_comments:
+    case (
+        pattern
+        # 1
+		as # 2
+        # 3
+		name #4
+        # 5
+    ):
+        pass
+
+
+match x:
+    case (a as b) as c:
+        pass
+
 match pattern_singleton:
     case (
         # leading 1
@@ -247,7 +276,7 @@ match newlines:
 
     case "NOT_YET_IMPLEMENTED_PatternMatchValue":
         pass
-    case x as NOT_YET_IMPLEMENTED_PatternMatchAs:
+    case _:
         pass
 
 
@@ -274,7 +303,7 @@ match long_lines:
 
 match pattern_comments:
     case (
-        x as NOT_YET_IMPLEMENTED_PatternMatchAs  # trailing 1
+        only_trailing  # trailing 1
         # trailing 2
         # trailing 3
     ):
@@ -284,7 +313,7 @@ match pattern_comments:
 match pattern_comments:
     case (
         # leading
-        x as NOT_YET_IMPLEMENTED_PatternMatchAs
+        only_leading
     ):
         pass
 
@@ -292,7 +321,7 @@ match pattern_comments:
 match pattern_comments:
     case (
         # leading
-        x as NOT_YET_IMPLEMENTED_PatternMatchAs  # trailing 1
+        leading_and_trailing  # trailing 1
         # trailing 2
         # trailing 3
     ):
@@ -300,10 +329,37 @@ match pattern_comments:
 
 
 match pattern_comments:
-    case (x as NOT_YET_IMPLEMENTED_PatternMatchAs):
+    case (no_comments):
         pass
 
 
+match pattern_comments:
+    case (
+        # 1
+        pattern as name  # 2
+        # 3
+        # 4
+        # 5  # 6
+        # 7
+    ):
+        pass
+
+
+match pattern_comments:
+    case (
+        pattern as name
+        # 1
+        # 2
+        # 3  # 4
+        # 5
+    ):
+        pass
+
+
+match x:
+    case (a as b) as c:
+        pass
+
 match pattern_singleton:
     case (
         # leading 1