[flake8_django] Fix DJ008 false positive for abstract models with type-annotated abstract field (#19221)

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ruff_linter/resources/test/fixtures/flake8_django/DJ008.py

@@ -181,3 +181,51 @@ class SubclassTestModel2(TestModel4):
 # Subclass without __str__
 class SubclassTestModel3(TestModel1):
     pass
+
+
+# Test cases for type-annotated abstract models - these should NOT trigger DJ008
+from typing import ClassVar
+from django_stubs_ext.db.models import TypedModelMeta
+
+
+class TypeAnnotatedAbstractModel1(models.Model):
+    """Model with type-annotated abstract = True - should not trigger DJ008"""
+    new_field = models.CharField(max_length=10)
+
+    class Meta(TypedModelMeta):
+        abstract: ClassVar[bool] = True
+
+
+class TypeAnnotatedAbstractModel2(models.Model):
+    """Model with type-annotated abstract = True using regular Meta - should not trigger DJ008"""  
+    new_field = models.CharField(max_length=10)
+
+    class Meta:
+        abstract: ClassVar[bool] = True
+
+
+class TypeAnnotatedAbstractModel3(models.Model):
+    """Model with type-annotated abstract = True but without ClassVar - should not trigger DJ008"""
+    new_field = models.CharField(max_length=10)
+
+    class Meta:
+        abstract: bool = True
+
+
+class TypeAnnotatedNonAbstractModel(models.Model):
+    """Model with type-annotated abstract = False - should trigger DJ008"""
+    new_field = models.CharField(max_length=10)
+
+    class Meta:
+        abstract: ClassVar[bool] = False
+
+
+class TypeAnnotatedAbstractModelWithStr(models.Model):
+    """Model with type-annotated abstract = True and __str__ method - should not trigger DJ008"""
+    new_field = models.CharField(max_length=10)
+
+    class Meta(TypedModelMeta):
+        abstract: ClassVar[bool] = True
+
+    def __str__(self):
+        return self.new_field

crates/ruff_linter/src/rules/flake8_django/rules/model_without_dunder_str.rs

@@ -96,22 +96,43 @@ fn is_model_abstract(class_def: &ast::StmtClassDef) -> bool {
             continue;
         }
         for element in body {
-            let Stmt::Assign(ast::StmtAssign { targets, value, .. }) = element else {
-                continue;
-            };
-            for target in targets {
-                let Expr::Name(ast::ExprName { id, .. }) = target else {
-                    continue;
-                };
-                if id != "abstract" {
-                    continue;
+            match element {
+                Stmt::Assign(ast::StmtAssign { targets, value, .. }) => {
+                    if targets
+                        .iter()
+                        .any(|target| is_abstract_true_assignment(target, Some(value)))
+                    {
+                        return true;
+                    }
                 }
-                if !is_const_true(value) {
-                    continue;
+                Stmt::AnnAssign(ast::StmtAnnAssign { target, value, .. }) => {
+                    if is_abstract_true_assignment(target, value.as_deref()) {
+                        return true;
+                    }
                 }
-                return true;
+                _ => {}
             }
         }
     }
     false
 }
+
+fn is_abstract_true_assignment(target: &Expr, value: Option<&Expr>) -> bool {
+    let Expr::Name(ast::ExprName { id, .. }) = target else {
+        return false;
+    };
+
+    if id != "abstract" {
+        return false;
+    }
+
+    let Some(value) = value else {
+        return false;
+    };
+
+    if !is_const_true(value) {
+        return false;
+    }
+
+    true
+}

crates/ruff_linter/src/rules/flake8_django/snapshots/ruff_linter__rules__flake8_django__tests__DJ008_DJ008.py.snap

@@ -1,6 +1,5 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_django/mod.rs
-snapshot_kind: text
 ---
 DJ008.py:6:7: DJ008 Model does not define `__str__` method
   |
@@ -31,3 +30,11 @@ DJ008.py:182:7: DJ008 Model does not define `__str__` method
     |       ^^^^^^^^^^^^^^^^^^ DJ008
 183 |     pass
     |
+
+DJ008.py:215:7: DJ008 Model does not define `__str__` method
+    |
+215 | class TypeAnnotatedNonAbstractModel(models.Model):
+    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ DJ008
+216 |     """Model with type-annotated abstract = False - should trigger DJ008"""
+217 |     new_field = models.CharField(max_length=10)
+    |