[`flake8-django`] Apply `DJ001` to annotated fields (#20907)

crates/ruff_linter/resources/test/fixtures/flake8_django/DJ001.py

@@ -46,3 +46,9 @@ class CorrectModel(models.Model):
         max_length=255, null=True, blank=True, unique=True
     )
     urlfieldu = models.URLField(max_length=255, null=True, blank=True, unique=True)
+
+
+class IncorrectModelWithSimpleAnnotations(models.Model):
+    charfield: models.CharField = models.CharField(max_length=255, null=True)
+    textfield: models.TextField = models.TextField(max_length=255, null=True)
+    slugfield: models.SlugField = models.SlugField(max_length=255, null=True)

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

@@ -61,9 +61,14 @@ pub(crate) fn nullable_model_string_field(checker: &Checker, body: &[Stmt]) {
     }
 
     for statement in body {
-        let Stmt::Assign(ast::StmtAssign { value, .. }) = statement else {
+        let value = match statement {
-            continue;
+            Stmt::Assign(ast::StmtAssign { value, .. }) => value,
+            Stmt::AnnAssign(ast::StmtAnnAssign {
+                value: Some(value), ..
+            }) => value,
+            _ => continue,
         };
+
         if let Some(field_name) = is_nullable_field(value, checker.semantic()) {
             checker.report_diagnostic(
                 DjangoNullableModelStringField {

crates/ruff_linter/src/rules/flake8_django/snapshots/ruff_linter__rules__flake8_django__tests__DJ001_DJ001.py.snap

@@ -186,3 +186,32 @@ DJ001 Avoid using `null=True` on string-based fields such as `URLField`
 30 |     urlfield = models.URLField(max_length=255, null=True)
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+
+DJ001 Avoid using `null=True` on string-based fields such as `CharField`
+  --> DJ001.py:52:35
+   |
+51 | class IncorrectModelWithSimpleAnnotations(models.Model):
+52 |     charfield: models.CharField = models.CharField(max_length=255, null=True)
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+53 |     textfield: models.TextField = models.TextField(max_length=255, null=True)
+54 |     slugfield: models.SlugField = models.SlugField(max_length=255, null=True)
+   |
+
+DJ001 Avoid using `null=True` on string-based fields such as `TextField`
+  --> DJ001.py:53:35
+   |
+51 | class IncorrectModelWithSimpleAnnotations(models.Model):
+52 |     charfield: models.CharField = models.CharField(max_length=255, null=True)
+53 |     textfield: models.TextField = models.TextField(max_length=255, null=True)
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+54 |     slugfield: models.SlugField = models.SlugField(max_length=255, null=True)
+   |
+
+DJ001 Avoid using `null=True` on string-based fields such as `SlugField`
+  --> DJ001.py:54:35
+   |
+52 |     charfield: models.CharField = models.CharField(max_length=255, null=True)
+53 |     textfield: models.TextField = models.TextField(max_length=255, null=True)
+54 |     slugfield: models.SlugField = models.SlugField(max_length=255, null=True)
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |