Remove parentheses around some walrus operators (#6173)

## Summary

Closes https://github.com/astral-sh/ruff/issues/5781

## Test Plan

Added cases to
`crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/named_expr.py`
one-by-one and adjusted the condition as needed.

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/named_expr.py

@@ -11,3 +11,28 @@ if (
 y0 = (y1 := f(x))
 
 f(x:=y, z=True)
+
+assert (x := 1)
+
+
+def f():
+    return (x := 1)
+
+
+for x in (y := [1, 2, 3]):
+    pass
+
+async for x in (y := [1, 2, 3]):
+    pass
+
+del (x := 1)
+
+try:
+    pass
+except (e := Exception):
+    if x := 1:
+        pass
+
+(x := 1)
+
+(x := 1) + (y := 2)

crates/ruff_python_formatter/src/expression/expr_named_expr.rs

@@ -32,11 +32,25 @@ impl FormatNodeRule<ExprNamedExpr> for FormatExprNamedExpr {
 impl NeedsParentheses for ExprNamedExpr {
     fn needs_parentheses(
         &self,
-        _parent: AnyNodeRef,
+        parent: AnyNodeRef,
         _context: &PyFormatContext,
     ) -> OptionalParentheses {
         // Unlike tuples, named expression parentheses are not part of the range even when
         // mandatory. See [PEP 572](https://peps.python.org/pep-0572/) for details.
+        if parent.is_stmt_ann_assign()
+            || parent.is_stmt_assign()
+            || parent.is_stmt_aug_assign()
+            || parent.is_stmt_assert()
+            || parent.is_stmt_return()
+            || parent.is_except_handler_except_handler()
+            || parent.is_with_item()
+            || parent.is_stmt_delete()
+            || parent.is_stmt_for()
+            || parent.is_stmt_async_for()
+        {
             OptionalParentheses::Always
+        } else {
+            OptionalParentheses::Never
+        }
     }
 }

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_38__pep_572.py.snap

@@ -1,196 +0,0 @@
----
-source: crates/ruff_python_formatter/tests/fixtures.rs
-input_file: crates/ruff_python_formatter/resources/test/fixtures/black/py_38/pep_572.py
----
-## Input
-
-```py
-(a := 1)
-(a := a)
-if (match := pattern.search(data)) is None:
-    pass
-if match := pattern.search(data):
-    pass
-[y := f(x), y**2, y**3]
-filtered_data = [y for x in data if (y := f(x)) is None]
-(y := f(x))
-y0 = (y1 := f(x))
-foo(x=(y := f(x)))
-
-
-def foo(answer=(p := 42)):
-    pass
-
-
-def foo(answer: (p := 42) = 5):
-    pass
-
-
-lambda: (x := 1)
-(x := lambda: 1)
-(x := lambda: (y := 1))
-lambda line: (m := re.match(pattern, line)) and m.group(1)
-x = (y := 0)
-(z := (y := (x := 0)))
-(info := (name, phone, *rest))
-(x := 1, 2)
-(total := total + tax)
-len(lines := f.readlines())
-foo(x := 3, cat="vector")
-foo(cat=(category := "vector"))
-if any(len(longline := l) >= 100 for l in lines):
-    print(longline)
-if env_base := os.environ.get("PYTHONUSERBASE", None):
-    return env_base
-if self._is_special and (ans := self._check_nans(context=context)):
-    return ans
-foo(b := 2, a=1)
-foo((b := 2), a=1)
-foo(c=(b := 2), a=1)
-
-while x := f(x):
-    pass
-while x := f(x):
-    pass
-```
-
-## Black Differences
-
-```diff
---- Black
-+++ Ruff
-@@ -2,7 +2,7 @@
- (a := a)
- if (match := pattern.search(data)) is None:
-     pass
--if match := pattern.search(data):
-+if (match := pattern.search(data)):
-     pass
- [y := f(x), y**2, y**3]
- filtered_data = [y for x in data if (y := f(x)) is None]
-@@ -33,7 +33,7 @@
- foo(cat=(category := "vector"))
- if any(len(longline := l) >= 100 for l in lines):
-     print(longline)
--if env_base := os.environ.get("PYTHONUSERBASE", None):
-+if (env_base := os.environ.get("PYTHONUSERBASE", None)):
-     return env_base
- if self._is_special and (ans := self._check_nans(context=context)):
-     return ans
-@@ -41,7 +41,7 @@
- foo((b := 2), a=1)
- foo(c=(b := 2), a=1)
- 
--while x := f(x):
-+while (x := f(x)):
-     pass
--while x := f(x):
-+while (x := f(x)):
-     pass
-```
-
-## Ruff Output
-
-```py
-(a := 1)
-(a := a)
-if (match := pattern.search(data)) is None:
-    pass
-if (match := pattern.search(data)):
-    pass
-[y := f(x), y**2, y**3]
-filtered_data = [y for x in data if (y := f(x)) is None]
-(y := f(x))
-y0 = (y1 := f(x))
-foo(x=(y := f(x)))
-
-
-def foo(answer=(p := 42)):
-    pass
-
-
-def foo(answer: (p := 42) = 5):
-    pass
-
-
-lambda: (x := 1)
-(x := lambda: 1)
-(x := lambda: (y := 1))
-lambda line: (m := re.match(pattern, line)) and m.group(1)
-x = (y := 0)
-(z := (y := (x := 0)))
-(info := (name, phone, *rest))
-(x := 1, 2)
-(total := total + tax)
-len(lines := f.readlines())
-foo(x := 3, cat="vector")
-foo(cat=(category := "vector"))
-if any(len(longline := l) >= 100 for l in lines):
-    print(longline)
-if (env_base := os.environ.get("PYTHONUSERBASE", None)):
-    return env_base
-if self._is_special and (ans := self._check_nans(context=context)):
-    return ans
-foo(b := 2, a=1)
-foo((b := 2), a=1)
-foo(c=(b := 2), a=1)
-
-while (x := f(x)):
-    pass
-while (x := f(x)):
-    pass
-```
-
-## Black Output
-
-```py
-(a := 1)
-(a := a)
-if (match := pattern.search(data)) is None:
-    pass
-if match := pattern.search(data):
-    pass
-[y := f(x), y**2, y**3]
-filtered_data = [y for x in data if (y := f(x)) is None]
-(y := f(x))
-y0 = (y1 := f(x))
-foo(x=(y := f(x)))
-
-
-def foo(answer=(p := 42)):
-    pass
-
-
-def foo(answer: (p := 42) = 5):
-    pass
-
-
-lambda: (x := 1)
-(x := lambda: 1)
-(x := lambda: (y := 1))
-lambda line: (m := re.match(pattern, line)) and m.group(1)
-x = (y := 0)
-(z := (y := (x := 0)))
-(info := (name, phone, *rest))
-(x := 1, 2)
-(total := total + tax)
-len(lines := f.readlines())
-foo(x := 3, cat="vector")
-foo(cat=(category := "vector"))
-if any(len(longline := l) >= 100 for l in lines):
-    print(longline)
-if env_base := os.environ.get("PYTHONUSERBASE", None):
-    return env_base
-if self._is_special and (ans := self._check_nans(context=context)):
-    return ans
-foo(b := 2, a=1)
-foo((b := 2), a=1)
-foo(c=(b := 2), a=1)
-
-while x := f(x):
-    pass
-while x := f(x):
-    pass
-```
-
-

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_39__python39.py.snap

@@ -32,19 +32,6 @@ def f():
  @relaxed_decorator[0]
  def f():
      ...
-@@ -13,8 +12,10 @@
-     ...
- 
- 
--@extremely_long_variable_name_that_doesnt_fit := complex.expression(
--    with_long="arguments_value_that_wont_fit_at_the_end_of_the_line"
-+@(
-+    extremely_long_variable_name_that_doesnt_fit := complex.expression(
-+        with_long="arguments_value_that_wont_fit_at_the_end_of_the_line"
-+    )
- )
- def f():
-     ...
 ```
 
 ## Ruff Output
@@ -64,11 +51,9 @@ def f():
     ...
 
 
-@(
+@extremely_long_variable_name_that_doesnt_fit := complex.expression(
-    extremely_long_variable_name_that_doesnt_fit := complex.expression(
     with_long="arguments_value_that_wont_fit_at_the_end_of_the_line"
 )
-)
 def f():
     ...
 ```

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

@@ -17,6 +17,31 @@ if (
 y0 = (y1 := f(x))
 
 f(x:=y, z=True)
+
+assert (x := 1)
+
+
+def f():
+    return (x := 1)
+
+
+for x in (y := [1, 2, 3]):
+    pass
+
+async for x in (y := [1, 2, 3]):
+    pass
+
+del (x := 1)
+
+try:
+    pass
+except (e := Exception):
+    if x := 1:
+        pass
+
+(x := 1)
+
+(x := 1) + (y := 2)
 ```
 
 ## Output
@@ -32,6 +57,31 @@ if (
 y0 = (y1 := f(x))
 
 f(x := y, z=True)
+
+assert (x := 1)
+
+
+def f():
+    return (x := 1)
+
+
+for x in (y := [1, 2, 3]):
+    pass
+
+async for x in (y := [1, 2, 3]):
+    pass
+
+del (x := 1)
+
+try:
+    pass
+except (e := Exception):
+    if x := 1:
+        pass
+
+(x := 1)
+
+(x := 1) + (y := 2)
 ```