Fixed #35024 -- Fixed model instance creation crash on GeneratedField.output_field with backend converters.

Regression in d9de74141e8a920940f1b91ed0a3ccb835b55729.

This is a long standing issue, however it caused a crash of
GeneratedFields for all output fields that have backend-specific
converters when the RETURNING clause is not supported
(MySQL and SQLite < 3.35).
That's why severity was exacerbated.

2 files changed, 20 insertions, 0 deletions

diff --git a/tests/model_fields/models.py b/tests/model_fields/models.py
index b4b7b5bd4c..aea02964e2 100644
--- a/tests/model_fields/models.py
+++ b/tests/model_fields/models.py
@@ -482,6 +482,18 @@ class UUIDGrandchild(UUIDChild):
     pass
 
 
+class GeneratedModelFieldWithConverters(models.Model):
+    field = models.UUIDField()
+    field_copy = models.GeneratedField(
+        expression=F("field"),
+        output_field=models.UUIDField(),
+        db_persist=True,
+    )
+
+    class Meta:
+        required_db_features = {"supports_stored_generated_columns"}
+
+
 class GeneratedModel(models.Model):
     a = models.IntegerField()
     b = models.IntegerField()
diff --git a/tests/model_fields/test_generatedfield.py b/tests/model_fields/test_generatedfield.py
index 9e5d9d87c3..056a80c294 100644
--- a/tests/model_fields/test_generatedfield.py
+++ b/tests/model_fields/test_generatedfield.py
@@ -1,3 +1,5 @@
+import uuid
+
 from django.apps import apps
 from django.db import IntegrityError, connection
 from django.db.models import (
@@ -14,6 +16,7 @@ from django.test.utils import isolate_apps
 
 from .models import (
     GeneratedModel,
+    GeneratedModelFieldWithConverters,
     GeneratedModelNull,
     GeneratedModelNullVirtual,
     GeneratedModelOutputFieldDbCollation,
@@ -266,6 +269,11 @@ class StoredGeneratedFieldTests(GeneratedFieldTestMixin, TestCase):
     output_field_db_collation_model = GeneratedModelOutputFieldDbCollation
     params_model = GeneratedModelParams
 
+    def test_create_field_with_db_converters(self):
+        obj = GeneratedModelFieldWithConverters.objects.create(field=uuid.uuid4())
+        obj = self._refresh_if_needed(obj)
+        self.assertEqual(obj.field, obj.field_copy)
+
 
 @skipUnlessDBFeature("supports_virtual_generated_columns")
 class VirtualGeneratedFieldTests(GeneratedFieldTestMixin, TestCase):