Remove unannotated attributes from RUF008 (#5049)

## Summary

In a dataclass:

```py
from dataclasses import dataclass

@DataClass
class X:
    class_var = {}
    x: int
```

`class_var` isn't actually a dataclass attribute, since it's
unannotated. This PR removes such attributes from RUF008
(`mutable-dataclass-default`), but it does enforce them in RUF012
(`mutable-class-default`), since those should be annotated with
`ClassVar` like any other mutable class attribute.

Closes #5043.

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

@@ -5,12 +5,11 @@
 KNOWINGLY_MUTABLE_DEFAULT = []
 
 
-@dataclass()
+@dataclass
 class A:
     mutable_default: list[int] = []
     immutable_annotation: typing.Sequence[int] = []
     without_annotation = []
-    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]] = []
@@ -21,7 +20,6 @@ class B:
     mutable_default: list[int] = []
     immutable_annotation: Sequence[int] = []
     without_annotation = []
-    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/RUF012.py

@@ -8,7 +8,6 @@ class A:
     mutable_default: list[int] = []
     immutable_annotation: typing.Sequence[int] = []
     without_annotation = []
-    ignored_via_comment: list[int] = []  # noqa: RUF012
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     class_variable: typing.ClassVar[list[int]] = []
 
@@ -17,6 +16,18 @@ class B:
     mutable_default: list[int] = []
     immutable_annotation: Sequence[int] = []
     without_annotation = []
-    ignored_via_comment: list[int] = []  # noqa: RUF012
     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
     class_variable: ClassVar[list[int]] = []
+
+
+from dataclasses import dataclass, field
+
+
+@dataclass
+class C:
+    mutable_default: list[int] = []
+    immutable_annotation: Sequence[int] = []
+    without_annotation = []
+    correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+    perfectly_fine: list[int] = field(default_factory=list)
+    class_variable: ClassVar[list[int]] = []

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

@@ -95,11 +95,8 @@ pub(crate) fn function_call_in_dataclass_default(
         }) = statement
         {
             if let Expr::Call(ast::ExprCall { func, .. }) = expr.as_ref() {
-                if is_class_var_annotation(checker.semantic_model(), annotation) {
-                    continue;
-                }
-
-                if !is_immutable_func(checker.semantic_model(), func, &extend_immutable_calls)
+                if !is_class_var_annotation(checker.semantic_model(), annotation)
+                    && !is_immutable_func(checker.semantic_model(), func, &extend_immutable_calls)
                     && !is_allowed_dataclass_function(checker.semantic_model(), func)
                 {
                     checker.diagnostics.push(Diagnostic::new(

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

@@ -45,10 +45,6 @@ impl Violation for MutableClassDefault {
 
 /// RUF012
 pub(crate) fn mutable_class_default(checker: &mut Checker, class_def: &ast::StmtClassDef) {
-    if is_dataclass(checker.semantic_model(), class_def) {
-        return;
-    }
-
     for statement in &class_def.body {
         match statement {
             Stmt::AnnAssign(ast::StmtAnnAssign {
@@ -59,6 +55,7 @@ pub(crate) fn mutable_class_default(checker: &mut Checker, class_def: &ast::Stmt
                 if is_mutable_expr(value)
                     && !is_class_var_annotation(checker.semantic_model(), annotation)
                     && !is_immutable_annotation(checker.semantic_model(), annotation)
+                    && !is_dataclass(checker.semantic_model(), class_def)
                 {
                     checker
                         .diagnostics

crates/ruff/src/rules/ruff/rules/mutable_dataclass_default.rs

@@ -8,17 +8,19 @@ use crate::checkers::ast::Checker;
 use crate::rules::ruff::rules::helpers::{is_class_var_annotation, is_dataclass, is_mutable_expr};
 
 /// ## What it does
-/// Checks for mutable default values in dataclasses.
+/// Checks for mutable default values in dataclass attributes.
 ///
 /// ## Why is this bad?
-/// Mutable default values share state across all instances of the dataclass,
-/// while not being obvious. This can lead to bugs when the attributes are
-/// changed in one instance, as those changes will unexpectedly affect all
-/// other instances.
+/// Mutable default values share state across all instances of the dataclass.
+/// This can lead to bugs when the attributes are changed in one instance, as
+/// those changes will unexpectedly affect all other instances.
 ///
 /// Instead of sharing mutable defaults, use the `field(default_factory=...)`
 /// pattern.
 ///
+/// If the default value is intended to be mutable, it should be annotated with
+/// `typing.ClassVar`.
+///
 /// ## Examples
 /// ```python
 /// from dataclasses import dataclass
@@ -38,6 +40,17 @@ use crate::rules::ruff::rules::helpers::{is_class_var_annotation, is_dataclass,
 /// class A:
 ///     mutable_default: list[int] = field(default_factory=list)
 /// ```
+///
+/// Or:
+/// ```python
+/// from dataclasses import dataclass, field
+/// from typing import ClassVar
+///
+///
+/// @dataclass
+/// class A:
+///     mutable_default: ClassVar[list[int]] = []
+/// ```
 #[violation]
 pub struct MutableDataclassDefault;
 
@@ -55,29 +68,20 @@ pub(crate) fn mutable_dataclass_default(checker: &mut Checker, class_def: &ast::
     }
 
     for statement in &class_def.body {
-        match statement {
-            Stmt::AnnAssign(ast::StmtAnnAssign {
-                annotation,
-                value: Some(value),
-                ..
-            }) => {
-                if is_mutable_expr(value)
-                    && !is_class_var_annotation(checker.semantic_model(), annotation)
-                    && !is_immutable_annotation(checker.semantic_model(), annotation)
-                {
-                    checker
-                        .diagnostics
-                        .push(Diagnostic::new(MutableDataclassDefault, value.range()));
-                }
-            }
-            Stmt::Assign(ast::StmtAssign { value, .. }) => {
-                if is_mutable_expr(value) {
-                    checker
-                        .diagnostics
-                        .push(Diagnostic::new(MutableDataclassDefault, value.range()));
-                }
+        if let Stmt::AnnAssign(ast::StmtAnnAssign {
+            annotation,
+            value: Some(value),
+            ..
+        }) = statement
+        {
+            if is_mutable_expr(value)
+                && !is_class_var_annotation(checker.semantic_model(), annotation)
+                && !is_immutable_annotation(checker.semantic_model(), annotation)
+            {
+                checker
+                    .diagnostics
+                    .push(Diagnostic::new(MutableDataclassDefault, value.range()));
             }
-            _ => (),
         }
     }
 }

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

@@ -3,42 +3,22 @@ source: crates/ruff/src/rules/ruff/mod.rs
 ---
 RUF008.py:10:34: RUF008 Do not use mutable default values for dataclass attributes
    |
- 8 | @dataclass()
+ 8 | @dataclass
  9 | class A:
 10 |     mutable_default: list[int] = []
    |                                  ^^ RUF008
 11 |     immutable_annotation: typing.Sequence[int] = []
 12 |     without_annotation = []
    |
 
-RUF008.py:12:26: RUF008 Do not use mutable default values for dataclass attributes
+RUF008.py:20:34: RUF008 Do not use mutable default values for dataclass attributes
    |
-10 |     mutable_default: list[int] = []
-11 |     immutable_annotation: typing.Sequence[int] = []
-12 |     without_annotation = []
-   |                          ^^ RUF008
-13 |     ignored_via_comment: list[int] = []  # noqa: RUF008
-14 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
-   |
-
-RUF008.py:21:34: RUF008 Do not use mutable default values for dataclass attributes
-   |
-19 | @dataclass
-20 | class B:
-21 |     mutable_default: list[int] = []
+18 | @dataclass
+19 | class B:
+20 |     mutable_default: list[int] = []
    |                                  ^^ RUF008
-22 |     immutable_annotation: Sequence[int] = []
-23 |     without_annotation = []
-   |
-
-RUF008.py:23:26: RUF008 Do not use mutable default values for dataclass attributes
-   |
-21 |     mutable_default: list[int] = []
-22 |     immutable_annotation: Sequence[int] = []
-23 |     without_annotation = []
-   |                          ^^ RUF008
-24 |     ignored_via_comment: list[int] = []  # noqa: RUF008
-25 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+21 |     immutable_annotation: Sequence[int] = []
+22 |     without_annotation = []
    |
 
 

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

@@ -16,27 +16,37 @@ RUF012.py:10:26: RUF012 Mutable class attributes should be annotated with `typin
  9 |     immutable_annotation: typing.Sequence[int] = []
 10 |     without_annotation = []
    |                          ^^ RUF012
-11 |     ignored_via_comment: list[int] = []  # noqa: RUF012
-12 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+11 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+12 |     class_variable: typing.ClassVar[list[int]] = []
    |
 
-RUF012.py:17:34: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
+RUF012.py:16:34: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
    |
-16 | class B:
-17 |     mutable_default: list[int] = []
+15 | class B:
+16 |     mutable_default: list[int] = []
    |                                  ^^ RUF012
-18 |     immutable_annotation: Sequence[int] = []
-19 |     without_annotation = []
+17 |     immutable_annotation: Sequence[int] = []
+18 |     without_annotation = []
    |
 
-RUF012.py:19:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
+RUF012.py:18:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
    |
-17 |     mutable_default: list[int] = []
-18 |     immutable_annotation: Sequence[int] = []
-19 |     without_annotation = []
+16 |     mutable_default: list[int] = []
+17 |     immutable_annotation: Sequence[int] = []
+18 |     without_annotation = []
    |                          ^^ RUF012
-20 |     ignored_via_comment: list[int] = []  # noqa: RUF012
-21 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+19 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+20 |     class_variable: ClassVar[list[int]] = []
+   |
+
+RUF012.py:30:26: RUF012 Mutable class attributes should be annotated with `typing.ClassVar`
+   |
+28 |     mutable_default: list[int] = []
+29 |     immutable_annotation: Sequence[int] = []
+30 |     without_annotation = []
+   |                          ^^ RUF012
+31 |     correct_code: list[int] = KNOWINGLY_MUTABLE_DEFAULT
+32 |     perfectly_fine: list[int] = field(default_factory=list)
    |