[pyupgrade] Avoid PEP-604 unions with typing.NamedTuple (UP007, UP045) (#18682)

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## Summary
Make `UP045` ignore `Optional[NamedTuple]` as `NamedTuple` is a function
(not a proper type). Rewriting it to `NamedTuple | None` breaks at
runtime. While type checkers currently accept `NamedTuple` as a type,
they arguably shouldn't. Therefore, we outright ignore it and don't
touch or lint on it.

For a more detailed discussion, see the linked issue.

## Test Plan
Added examples to the existing tests.

## Related Issues
Fixes: https://github.com/astral-sh/ruff/issues/18619

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP007.py

@@ -90,3 +90,52 @@ class AClass:
 
 def myfunc(param: "tuple[Union[int, 'AClass', None], str]"):
     print(param)
+
+
+from typing import NamedTuple, Union
+
+import typing_extensions
+from typing_extensions import (
+    NamedTuple as NamedTupleTE,
+    Union as UnionTE,
+)
+
+# Regression test for https://github.com/astral-sh/ruff/issues/18619
+# Don't emit lint for `NamedTuple`
+a_plain_1: Union[NamedTuple, int] = None
+a_plain_2: Union[int, NamedTuple] = None
+a_plain_3: Union[NamedTuple, None] = None
+a_plain_4: Union[None, NamedTuple] = None
+a_plain_te_1: UnionTE[NamedTupleTE, int] = None
+a_plain_te_2: UnionTE[int, NamedTupleTE] = None
+a_plain_te_3: UnionTE[NamedTupleTE, None] = None
+a_plain_te_4: UnionTE[None, NamedTupleTE] = None
+a_plain_typing_1: UnionTE[typing.NamedTuple, int] = None
+a_plain_typing_2: UnionTE[int, typing.NamedTuple] = None
+a_plain_typing_3: UnionTE[typing.NamedTuple, None] = None
+a_plain_typing_4: UnionTE[None, typing.NamedTuple] = None
+a_string_1: "Union[NamedTuple, int]" = None
+a_string_2: "Union[int, NamedTuple]" = None
+a_string_3: "Union[NamedTuple, None]" = None
+a_string_4: "Union[None, NamedTuple]" = None
+a_string_te_1: "UnionTE[NamedTupleTE, int]" = None
+a_string_te_2: "UnionTE[int, NamedTupleTE]" = None
+a_string_te_3: "UnionTE[NamedTupleTE, None]" = None
+a_string_te_4: "UnionTE[None, NamedTupleTE]" = None
+a_string_typing_1: "typing.Union[typing.NamedTuple, int]" = None
+a_string_typing_2: "typing.Union[int, typing.NamedTuple]" = None
+a_string_typing_3: "typing.Union[typing.NamedTuple, None]" = None
+a_string_typing_4: "typing.Union[None, typing.NamedTuple]" = None
+
+b_plain_1: Union[NamedTuple] = None
+b_plain_2: Union[NamedTuple, None] = None
+b_plain_te_1: UnionTE[NamedTupleTE] = None
+b_plain_te_2: UnionTE[NamedTupleTE, None] = None
+b_plain_typing_1: UnionTE[typing.NamedTuple] = None
+b_plain_typing_2: UnionTE[typing.NamedTuple, None] = None
+b_string_1: "Union[NamedTuple]" = None
+b_string_2: "Union[NamedTuple, None]" = None
+b_string_te_1: "UnionTE[NamedTupleTE]" = None
+b_string_te_2: "UnionTE[NamedTupleTE, None]" = None
+b_string_typing_1: "typing.Union[typing.NamedTuple]" = None
+b_string_typing_2: "typing.Union[typing.NamedTuple, None]" = None

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP045.py

@@ -47,3 +47,25 @@ class ServiceRefOrValue:
 # Test for: https://github.com/astral-sh/ruff/issues/18508
 # Optional[None] should not be offered a fix
 foo: Optional[None] = None
+
+
+from typing import NamedTuple, Optional
+
+import typing_extensions
+from typing_extensions import (
+    NamedTuple as NamedTupleTE,
+    Optional as OptionalTE,
+)
+
+# Regression test for https://github.com/astral-sh/ruff/issues/18619
+# Don't emit lint for `NamedTuple`
+a1: Optional[NamedTuple] = None
+a2: typing.Optional[NamedTuple] = None
+a3: OptionalTE[NamedTuple] = None
+a4: typing_extensions.Optional[NamedTuple] = None
+a5: Optional[typing.NamedTuple] = None
+a6: typing.Optional[typing.NamedTuple] = None
+a7: OptionalTE[typing.NamedTuple] = None
+a8: typing_extensions.Optional[typing.NamedTuple] = None
+a9: "Optional[NamedTuple]" = None
+a10: Optional[NamedTupleTE] = None

crates/ruff_linter/src/rules/pyupgrade/rules/use_pep604_annotation.rs

@@ -132,6 +132,17 @@ pub(crate) fn non_pep604_annotation(
     slice: &Expr,
     operator: Pep604Operator,
 ) {
+    // `NamedTuple` is not a type; it's a type constructor. Using it in a type annotation doesn't
+    // make much sense. But since type checkers will currently (incorrectly) _not_ complain about it
+    // being used in a type annotation, we just ignore `Optional[typing.NamedTuple]` and
+    // `Union[...]` containing `NamedTuple`.
+    // <https://github.com/astral-sh/ruff/issues/18619>
+    if is_optional_named_tuple(checker, operator, slice)
+        || is_union_with_named_tuple(checker, operator, slice)
+    {
+        return;
+    }
+
     // Avoid fixing forward references, types not in an annotation, and expressions that would
     // lead to invalid syntax.
     let fixable = checker.semantic().in_type_definition()
@@ -273,6 +284,25 @@ fn is_allowed_value(expr: &Expr) -> bool {
     }
 }
 
+/// Return `true` if this is an `Optional[typing.NamedTuple]` annotation.
+fn is_optional_named_tuple(checker: &Checker, operator: Pep604Operator, slice: &Expr) -> bool {
+    matches!(operator, Pep604Operator::Optional) && is_named_tuple(checker, slice)
+}
+
+/// Return `true` if this is a `Union[...]` annotation containing `typing.NamedTuple`.
+fn is_union_with_named_tuple(checker: &Checker, operator: Pep604Operator, slice: &Expr) -> bool {
+    matches!(operator, Pep604Operator::Union)
+        && (is_named_tuple(checker, slice)
+            || slice
+                .as_tuple_expr()
+                .is_some_and(|tuple| tuple.elts.iter().any(|elt| is_named_tuple(checker, elt))))
+}
+
+/// Return `true` if this is a `typing.NamedTuple` annotation.
+fn is_named_tuple(checker: &Checker, expr: &Expr) -> bool {
+    checker.semantic().match_typing_expr(expr, "NamedTuple")
+}
+
 /// Return `true` if this is an `Optional[None]` annotation.
 fn is_optional_none(operator: Pep604Operator, slice: &Expr) -> bool {
     matches!(operator, Pep604Operator::Optional) && matches!(slice, Expr::NoneLiteral(_))

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP007.py.snap

@@ -314,3 +314,5 @@ UP007.py:91:26: UP007 [*] Use `X | Y` for type annotations
 91    |-def myfunc(param: "tuple[Union[int, 'AClass', None], str]"):
    91 |+def myfunc(param: "tuple[int | 'AClass' | None, str]"):
 92 92 |     print(param)
+93 93 | 
+94 94 |