Allow typing.Final for mutable-class-default annotations (RUF012)

crates/ruff/resources/test/fixtures/ruff/RUF012.py

@@ -1,5 +1,5 @@
 import typing
-from typing import ClassVar, Sequence
+from typing import ClassVar, Sequence, Final
 
 KNOWINGLY_MUTABLE_DEFAULT = []
 
@@ -10,6 +10,7 @@ class A:
     without_annotation = []
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     class_variable: typing.ClassVar[list[int]] = []
+    final_variable: typing.Final[list[int]] = []
 
 
 class B:
@@ -18,6 +19,7 @@ class B:
     without_annotation = []
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     class_variable: ClassVar[list[int]] = []
+    final_variable: Final[list[int]] = []
 
 
 from dataclasses import dataclass, field
@@ -31,6 +33,7 @@ class C:
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     perfectly_fine: list[int] = field(default_factory=list)
     class_variable: ClassVar[list[int]] = []
+    final_variable: Final[list[int]] = []
 
 
 from pydantic import BaseModel
@@ -43,3 +46,4 @@ class D(BaseModel):
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     perfectly_fine: list[int] = field(default_factory=list)
     class_variable: ClassVar[list[int]] = []
+    final_variable: Final[list[int]] = []

crates/ruff/src/rules/ruff/rules/function_call_in_dataclass_default.rs

@@ -55,7 +55,7 @@ use crate::rules::ruff::rules::helpers::{
 /// - `flake8-bugbear.extend-immutable-calls`
 #[violation]
 pub struct FunctionCallInDataclassDefaultArgument {
-    pub name: Option<String>,
+    name: Option<String>,
 }
 
 impl Violation for FunctionCallInDataclassDefaultArgument {

crates/ruff/src/rules/ruff/rules/helpers.rs

@@ -18,6 +18,14 @@ pub(super) fn is_class_var_annotation(annotation: &Expr, semantic: &SemanticMode
     semantic.match_typing_expr(value, "ClassVar")
 }
 
+/// Returns `true` if the given [`Expr`] is a `typing.Final` annotation.
+pub(super) fn is_final_annotation(annotation: &Expr, semantic: &SemanticModel) -> bool {
+    let Expr::Subscript(ast::ExprSubscript { value, .. }) = &annotation else {
+        return false;
+    };
+    semantic.match_typing_expr(value, "Final")
+}
+
 /// Returns `true` if the given class is a dataclass.
 pub(super) fn is_dataclass(class_def: &ast::StmtClassDef, semantic: &SemanticModel) -> bool {
     class_def.decorator_list.iter().any(|decorator| {

crates/ruff/src/rules/ruff/rules/mutable_class_default.rs

@@ -6,7 +6,7 @@ use ruff_python_semantic::analyze::typing::{is_immutable_annotation, is_mutable_
 
 use crate::checkers::ast::Checker;
 use crate::rules::ruff::rules::helpers::{
-    is_class_var_annotation, is_dataclass, is_pydantic_model,
+    is_class_var_annotation, is_dataclass, is_final_annotation, is_pydantic_model,
 };
 
 /// ## What it does
@@ -56,6 +56,7 @@ pub(crate) fn mutable_class_default(checker: &mut Checker, class_def: &ast::Stmt
             }) => {
                 if is_mutable_expr(value, checker.semantic())
                     && !is_class_var_annotation(annotation, checker.semantic())
+                    && !is_final_annotation(annotation, checker.semantic())
                     && !is_immutable_annotation(annotation, checker.semantic())
                     && !is_dataclass(class_def, checker.semantic())
                 {

crates/ruff/src/rules/ruff/snapshots/ruff__rules__ruff__tests__RUF012_RUF012.py.snap

@@ -20,33 +20,33 @@ RUF012.py:10:26: RUF012 Mutable class attributes should be annotated with `typin
 12 |     class_variable: typing.ClassVar[list[int]] = []
    |
 
-RUF012.py:16:34: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
+RUF012.py:17:34: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
    |
-15 | class B:
-16 |     mutable_default: list[int] = []
+16 | class B:
+17 |     mutable_default: list[int] = []
    |                                  ^^ RUF012
-17 |     immutable_annotation: Sequence[int] = []
-18 |     without_annotation = []
+18 |     immutable_annotation: Sequence[int] = []
+19 |     without_annotation = []
    |
 
-RUF012.py:18:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
+RUF012.py:19:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
    |
-16 |     mutable_default: list[int] = []
-17 |     immutable_annotation: Sequence[int] = []
-18 |     without_annotation = []
+17 |     mutable_default: list[int] = []
+18 |     immutable_annotation: Sequence[int] = []
+19 |     without_annotation = []
    |                          ^^ RUF012
-19 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
-20 |     class_variable: ClassVar[list[int]] = []
+20 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+21 |     class_variable: ClassVar[list[int]] = []
    |
 
-RUF012.py:30:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
+RUF012.py:32:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
    |
-28 |     mutable_default: list[int] = []
-29 |     immutable_annotation: Sequence[int] = []
-30 |     without_annotation = []
+30 |     mutable_default: list[int] = []
+31 |     immutable_annotation: Sequence[int] = []
+32 |     without_annotation = []
    |                          ^^ RUF012
-31 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
-32 |     perfectly_fine: list[int] = field(default_factory=list)
+33 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+34 |     perfectly_fine: list[int] = field(default_factory=list)
    |