fix: Preserve standalone named expression parentheses

packages/griffelib/src/griffe/_internal/expressions.py

@@ -58,7 +58,6 @@ class _OperatorPrecedence(IntEnum):
     NONE = auto()
 
     YIELD = auto()  # `yield`, `yield from`
-    ASSIGN = auto()  # `target := expr`
     STARRED = auto()  # `*expr` (omitted by Python docs, see ruff impl)
     LAMBDA = auto()
     IF_ELSE = auto()  # `expr if cond else expr`
@@ -953,10 +952,12 @@ class ExprNamedExpr(Expr):
     """Value."""
 
     def iterate(self, *, flat: bool = True) -> Iterator[str | Expr]:
+        yield "("
         yield from _yield(self.target, flat=flat, outer_precedence=_OperatorPrecedence.NONE)
         yield " := "
-        # Nested walrus assignments and yields need parentheses, e.g. `a := (b := c)`.
+        # Yield expressions need parentheses on the right.
         yield from _yield(self.value, flat=flat, outer_precedence=_OperatorPrecedence.STARRED)
+        yield ")"
 
 
 @dataclass(eq=True, slots=True)
@@ -1252,7 +1253,8 @@ def iterate(self, *, flat: bool = True) -> Iterator[str | Expr]:
     ExprBoolOp: lambda e: {"and": _OperatorPrecedence.AND, "or": _OperatorPrecedence.OR}[e.operator],
     ExprCompare: lambda _: _OperatorPrecedence.COMP_MEMB_ID,
     ExprIfExp: lambda _: _OperatorPrecedence.IF_ELSE,
-    ExprNamedExpr: lambda _: _OperatorPrecedence.ASSIGN,
+    # Named expressions emit their own parentheses.
+    ExprNamedExpr: lambda _: _OperatorPrecedence.ATOMIC,
     ExprLambda: lambda _: _OperatorPrecedence.LAMBDA,
     ExprGeneratorExp: lambda _: _OperatorPrecedence.ATOMIC,
     ExprVarPositional: lambda _: _OperatorPrecedence.STARRED,

packages/griffelib/tests/test_expressions.py

@@ -218,6 +218,23 @@ def test_nested_container_format_spec_is_roundtrip_safe() -> None:
     assert ast.dump(reparsed) == ast.dump(original), f"{code!r} rendered as {rendered!r}"
 
 
+@pytest.mark.parametrize("flat", [True, False])
+def test_standalone_named_expression_is_roundtrip_safe(flat: bool) -> None:
+    """Standalone named expressions must retain their required parentheses."""
+    code = "(value := 1)"
+    original = ast.parse(code, mode="eval")
+    expression = get_expression(original.body, parent=Module("module"), parse_strings=False)
+    assert expression is not None
+
+    rendered = str(expression)
+
+    # Both iteration modes must preserve the parentheses required by standalone walrus expressions.
+    assert "".join(str(element) for element in expression.iterate(flat=flat)) == rendered
+
+    reparsed = ast.parse(rendered, mode="eval")
+    assert ast.dump(reparsed) == ast.dump(original), f"{code!r} rendered as {rendered!r}"
+
+
 @pytest.mark.parametrize(
     "code",
     [
@@ -253,7 +270,7 @@ def test_nested_tuples_keep_parentheses_in_implicit_contexts(code: str) -> None:
         ("o[(x, y) == z]", "o[(x, y) == z]"),
         ("o[(x, y) if condition else z]", "o[(x, y) if condition else z]"),
         ("o[lambda: (x, y)]", "o[lambda: (x, y)]"),
-        ("o[(item := (x, y))]", "o[item := (x, y)]"),
+        ("o[(item := (x, y))]", "o[(item := (x, y))]"),
         ("o[f'{(x, y)}']", "o[f'{(x, y)}']"),
         ("o[((x, y) for value in values)]", "o[((x, y) for value in values)]"),
         ("o[await (x, y)]", "o[await (x, y)]"),