Ignore ClassVar annotation for RUF008, RUF009 (#4081)

crates/ruff/resources/test/fixtures/ruff/RUF008.py

@@ -1,6 +1,6 @@
 import typing
 from dataclasses import dataclass, field
-from typing import Sequence
+from typing import ClassVar, Sequence
 
 KNOWINGLY_MUTABLE_DEFAULT = []
 
@@ -13,6 +13,7 @@ class A:
     ignored_via_comment: list[int] = []  # noqa: RUF008
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     perfectly_fine: list[int] = field(default_factory=list)
+    class_variable: typing.ClassVar[list[int]] = []
 
 
 @dataclass
@@ -23,3 +24,4 @@ class B:
     ignored_via_comment: list[int] = []  # noqa: RUF008
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     perfectly_fine: list[int] = field(default_factory=list)
+    class_variable: ClassVar[list[int]] = []

crates/ruff/resources/test/fixtures/ruff/RUF009.py

@@ -1,5 +1,6 @@
+import typing
 from dataclasses import dataclass
-from typing import NamedTuple
+from typing import ClassVar, NamedTuple
 
 
 def default_function() -> list[int]:
@@ -13,6 +14,8 @@ class ImmutableType(NamedTuple):
 @dataclass()
 class A:
     hidden_mutable_default: list[int] = default_function()
+    class_variable: typing.ClassVar[list[int]] = default_function()
+    another_class_var: ClassVar[list[int]] = default_function()
 
 
 DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES = ImmutableType(40)

crates/ruff/src/rules/ruff/rules/mutable_defaults_in_dataclass_fields.rs

@@ -151,13 +151,26 @@ fn is_allowed_func(context: &Context, func: &Expr) -> bool {
     })
 }
 
+/// Returns `true` if the given [`Expr`] is a `typing.ClassVar` annotation.
+fn is_class_var_annotation(context: &Context, annotation: &Expr) -> bool {
+    let ExprKind::Subscript { value, .. } = &annotation.node else {
+        return false;
+    };
+    context.match_typing_expr(value, "ClassVar")
+}
+
 /// RUF009
 pub fn function_call_in_dataclass_defaults(checker: &mut Checker, body: &[Stmt]) {
     for statement in body {
         if let StmtKind::AnnAssign {
-            value: Some(expr), ..
+            annotation,
+            value: Some(expr),
+            ..
         } = &statement.node
         {
+            if is_class_var_annotation(&checker.ctx, annotation) {
+                continue;
+            }
             if let ExprKind::Call { func, .. } = &expr.node {
                 if !is_allowed_func(&checker.ctx, func) {
                     checker.diagnostics.push(Diagnostic::new(
@@ -181,7 +194,10 @@ pub fn mutable_dataclass_default(checker: &mut Checker, body: &[Stmt]) {
                 value: Some(value),
                 ..
             } => {
-                if !is_immutable_annotation(&checker.ctx, annotation) && is_mutable_expr(value) {
+                if !is_class_var_annotation(&checker.ctx, annotation)
+                    && !is_immutable_annotation(&checker.ctx, annotation)
+                    && is_mutable_expr(value)
+                {
                     checker
                         .diagnostics
                         .push(Diagnostic::new(MutableDataclassDefault, Range::from(value)));

crates/ruff/src/rules/ruff/snapshots/ruff__rules__ruff__tests__RUF008_RUF008.py.snap

@@ -21,24 +21,24 @@ RUF008.py:12:26: RUF008 Do not use mutable default values for dataclass attribut
 16 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
    |
 
-RUF008.py:20:34: RUF008 Do not use mutable default values for dataclass attributes
+RUF008.py:21:34: RUF008 Do not use mutable default values for dataclass attributes
    |
-20 | @dataclass
-21 | class B:
-22 |     mutable_default: list[int] = []
+21 | @dataclass
+22 | class B:
+23 |     mutable_default: list[int] = []
    |                                  ^^ RUF008
-23 |     immutable_annotation: Sequence[int] = []
-24 |     without_annotation = []
+24 |     immutable_annotation: Sequence[int] = []
+25 |     without_annotation = []
    |
 
-RUF008.py:22:26: RUF008 Do not use mutable default values for dataclass attributes
+RUF008.py:23:26: RUF008 Do not use mutable default values for dataclass attributes
    |
-22 |     mutable_default: list[int] = []
-23 |     immutable_annotation: Sequence[int] = []
-24 |     without_annotation = []
+23 |     mutable_default: list[int] = []
+24 |     immutable_annotation: Sequence[int] = []
+25 |     without_annotation = []
    |                          ^^ RUF008
-25 |     ignored_via_comment: list[int] = []  # noqa: RUF008
-26 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+26 |     ignored_via_comment: list[int] = []  # noqa: RUF008
+27 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
    |
 
 

crates/ruff/src/rules/ruff/snapshots/ruff__rules__ruff__tests__RUF009_RUF009.py.snap

@@ -1,42 +1,44 @@
 ---
 source: crates/ruff/src/rules/ruff/mod.rs
 ---
-RUF009.py:15:41: RUF009 Do not perform function call `default_function` in dataclass defaults
+RUF009.py:16:41: RUF009 Do not perform function call `default_function` in dataclass defaults
    |
-15 | @dataclass()
-16 | class A:
-17 |     hidden_mutable_default: list[int] = default_function()
+16 | @dataclass()
+17 | class A:
+18 |     hidden_mutable_default: list[int] = default_function()
    |                                         ^^^^^^^^^^^^^^^^^^ RUF009
+19 |     class_variable: typing.ClassVar[list[int]] = default_function()
+20 |     another_class_var: ClassVar[list[int]] = default_function()
    |
 
-RUF009.py:24:41: RUF009 Do not perform function call `default_function` in dataclass defaults
+RUF009.py:27:41: RUF009 Do not perform function call `default_function` in dataclass defaults
    |
-24 | @dataclass
-25 | class B:
-26 |     hidden_mutable_default: list[int] = default_function()
+27 | @dataclass
+28 | class B:
+29 |     hidden_mutable_default: list[int] = default_function()
    |                                         ^^^^^^^^^^^^^^^^^^ RUF009
-27 |     another_dataclass: A = A()
-28 |     not_optimal: ImmutableType = ImmutableType(20)
+30 |     another_dataclass: A = A()
+31 |     not_optimal: ImmutableType = ImmutableType(20)
    |
 
-RUF009.py:25:28: RUF009 Do not perform function call `A` in dataclass defaults
+RUF009.py:28:28: RUF009 Do not perform function call `A` in dataclass defaults
    |
-25 | class B:
-26 |     hidden_mutable_default: list[int] = default_function()
-27 |     another_dataclass: A = A()
+28 | class B:
+29 |     hidden_mutable_default: list[int] = default_function()
+30 |     another_dataclass: A = A()
    |                            ^^^ RUF009
-28 |     not_optimal: ImmutableType = ImmutableType(20)
-29 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
+31 |     not_optimal: ImmutableType = ImmutableType(20)
+32 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
    |
 
-RUF009.py:26:34: RUF009 Do not perform function call `ImmutableType` in dataclass defaults
+RUF009.py:29:34: RUF009 Do not perform function call `ImmutableType` in dataclass defaults
    |
-26 |     hidden_mutable_default: list[int] = default_function()
-27 |     another_dataclass: A = A()
-28 |     not_optimal: ImmutableType = ImmutableType(20)
+29 |     hidden_mutable_default: list[int] = default_function()
+30 |     another_dataclass: A = A()
+31 |     not_optimal: ImmutableType = ImmutableType(20)
    |                                  ^^^^^^^^^^^^^^^^^ RUF009
-29 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
-30 |     okay_variant: A = DEFAULT_A_FOR_ALL_DATACLASSES
+32 |     good_variant: ImmutableType = DEFAULT_IMMUTABLETYPE_FOR_ALL_DATACLASSES
+33 |     okay_variant: A = DEFAULT_A_FOR_ALL_DATACLASSES
    |