Fixed #25253 -- Made AlterField operation a noop when changing attributes that don't affect the schema.

1 files changed, 29 insertions, 0 deletions

diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index 49fda069d3..e41db7a500 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -2758,6 +2758,35 @@ class SchemaTests(TransactionTestCase):
         with connection.schema_editor() as editor, self.assertNumQueries(0):
             editor.alter_field(AuthorWithDefaultHeight, old_field, new_field, strict=True)
 
+    @skipUnlessDBFeature('supports_foreign_keys')
+    def test_alter_field_fk_attributes_noop(self):
+        """
+        No queries are performed when changing field attributes that don't
+        affect the schema.
+        """
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+            editor.create_model(Book)
+        old_field = Book._meta.get_field('author')
+        new_field = ForeignKey(
+            Author,
+            blank=True,
+            editable=False,
+            error_messages={'invalid': 'error message'},
+            help_text='help text',
+            limit_choices_to={'limit': 'choice'},
+            on_delete=PROTECT,
+            related_name='related_name',
+            related_query_name='related_query_name',
+            validators=[lambda x: x],
+            verbose_name='verbose name',
+        )
+        new_field.set_attributes_from_name('author')
+        with connection.schema_editor() as editor, self.assertNumQueries(0):
+            editor.alter_field(Book, old_field, new_field, strict=True)
+        with connection.schema_editor() as editor, self.assertNumQueries(0):
+            editor.alter_field(Book, new_field, old_field, strict=True)
+
     def test_add_textfield_unhashable_default(self):
         # Create the table
         with connection.schema_editor() as editor: