Ticket #34219: test-34219.diff

tests/schema/tests.py

@@ -4950 +4950 @@
             editor.alter_field(Author, new_field, old_field, strict=True)
         self.assertIsNone(self.get_column_collation(Author._meta.db_table, "name"))
 
+    @skipUnlessDBFeature("supports_collation_on_charfield")
+    def test_alter_field_type_preserve_db_collation(self):
+        collation = connection.features.test_collations.get("non_default")
+        if not collation:
+            self.skipTest("Language collations are not supported.")
+
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+
+        old_field = Author._meta.get_field("name")
+        new_field = CharField(max_length=255, db_collation=collation)
+        new_field.set_attributes_from_name("name")
+        new_field.model = Author
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, old_field, new_field, strict=True)
+        self.assertEqual(
+            self.get_column_collation(Author._meta.db_table, "name"),
+            collation,
+        )
+        # Changing a field type should preserve the collation.
+        old_field = new_field
+        new_field = CharField(max_length=511, db_collation=collation)
+        new_field.set_attributes_from_name("name")
+        new_field.model = Author
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, new_field, old_field, strict=True)
+        # Collation is preserved.
+        self.assertEqual(
+            self.get_column_collation(Author._meta.db_table, "name"),
+            collation,
+        )
+
     @skipUnlessDBFeature("supports_collation_on_charfield")
     def test_alter_primary_key_db_collation(self):
         collation = connection.features.test_collations.get("non_default")