Fixed #23408 -- Added migrations questioner prompt for adding unique fields with a callable default.

tests/migrations/test_commands.py

@@ -17,6 +17,8 @@ from django.db.migrations.exceptions import InconsistentMigrationHistory
 from django.db.migrations.recorder import MigrationRecorder
 from django.test import TestCase, override_settings, skipUnlessDBFeature
 from django.test.utils import captured_stdout
+from django.utils import timezone
+from django.utils.version import get_docs_version
 
 from .models import UnicodeModel, UnserializableModel
 from .routers import TestRouter
@@ -1870,6 +1872,57 @@ class MakeMigrationsTests(MigrationTestBase):
                 with self.assertRaises(SystemExit):
                     call_command('makemigrations', 'migrations', interactive=True)
 
+    def test_makemigrations_interactive_unique_callable_default_addition(self):
+        """
+        makemigrations prompts the user when adding a unique field with
+        a callable default.
+        """
+        class Book(models.Model):
+            created = models.DateTimeField(unique=True, default=timezone.now)
+
+            class Meta:
+                app_label = 'migrations'
+
+        version = get_docs_version()
+        input_msg = (
+            f'Callable default on unique field book.created will not generate '
+            f'unique values upon migrating.\n'
+            f'Please choose how to proceed:\n\n'
+            f' 1) Continue making this migration as the first step in writing '
+            f'a manual migration to generate unique values described here: '
+            f'https://docs.djangoproject.com/en/{version}/howto/'
+            f'writing-migrations/#migrations-that-add-unique-fields.\n'
+            f' 2) Quit and edit field options in models.py.\n'
+        )
+        with self.temporary_migration_module(module='migrations.test_migrations'):
+            # 2 - quit.
+            with mock.patch('builtins.input', return_value='2'):
+                with captured_stdout() as out, self.assertRaises(SystemExit):
+                    call_command('makemigrations', 'migrations', interactive=True)
+            out_value = out.getvalue()
+            self.assertIn(input_msg, out_value)
+            self.assertNotIn('Add field created to book', out_value)
+            # 1 - continue.
+            with mock.patch('builtins.input', return_value='1'):
+                with captured_stdout() as out:
+                    call_command('makemigrations', 'migrations', interactive=True)
+            out_value = out.getvalue()
+            self.assertIn(input_msg, out_value)
+            self.assertIn('Add field created to book', out_value)
+
+    def test_makemigrations_non_interactive_unique_callable_default_addition(self):
+        class Book(models.Model):
+            created = models.DateTimeField(unique=True, default=timezone.now)
+
+            class Meta:
+                app_label = 'migrations'
+
+        with self.temporary_migration_module(module='migrations.test_migrations'):
+            with captured_stdout() as out:
+                call_command('makemigrations', 'migrations', interactive=False)
+            out_value = out.getvalue()
+            self.assertIn('Add field created to book', out_value)
+
 
 class SquashMigrationsTests(MigrationTestBase):
     """