Fixed #24755 -- Hid operations from dependency apps when merging migrations

Thanks Carl Meyer for the report and Tim Graham for the review.

django/core/management/commands/makemigrations.py

@@ -194,13 +194,17 @@ class Command(BaseCommand):
             questioner = InteractiveMigrationQuestioner()
         else:
             questioner = MigrationQuestioner(defaults={'ask_merge': True})
+
         for app_label, migration_names in conflicts.items():
             # Grab out the migrations in question, and work out their
             # common ancestor.
             merge_migrations = []
             for migration_name in migration_names:
                 migration = loader.get_migration(app_label, migration_name)
-                migration.ancestry = loader.graph.forwards_plan((app_label, migration_name))
+                migration.ancestry = [
+                    mig for mig in loader.graph.forwards_plan((app_label, migration_name))
+                    if mig[0] == migration.app_label
+                ]
                 merge_migrations.append(migration)
             all_items_equal = lambda seq: all(item == seq[0] for item in seq[1:])
             merge_migrations_generations = zip(*[m.ancestry for m in merge_migrations])

tests/migrations/migrations_test_apps/conflicting_app_with_dependencies/migrations/0001_initial.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    operations = [
+        migrations.CreateModel(
+            "Author",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("name", models.CharField(max_length=255)),
+                ("slug", models.SlugField(null=True)),
+                ("age", models.IntegerField(default=0)),
+                ("silly_field", models.BooleanField(default=False)),
+            ],
+        ),
+        migrations.CreateModel(
+            "Tribble",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("fluffy", models.BooleanField(default=True)),
+            ],
+        )
+    ]

tests/migrations/migrations_test_apps/conflicting_app_with_dependencies/migrations/0002_conflicting_second.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("conflicting_app_with_dependencies", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            "Something",
+            [
+                ("id", models.AutoField(primary_key=True)),
+            ],
+        )
+    ]

tests/migrations/migrations_test_apps/conflicting_app_with_dependencies/migrations/0002_second.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("conflicting_app_with_dependencies", "0001_initial"),
+        ("migrated_app", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.DeleteModel("Tribble"),
+        migrations.RemoveField("Author", "silly_field"),
+        migrations.AddField("Author", "rating", models.IntegerField(default=0)),
+        migrations.CreateModel(
+            "Book",
+            [
+                ("id", models.AutoField(primary_key=True)),
+            ],
+        )
+    ]

tests/migrations/test_commands.py

@@ -920,6 +920,39 @@ class MakeMigrationsTests(MigrationTestBase):
             except CommandError:
                 self.fail("Makemigrations fails resolving conflicts in an unspecified app")
 
+    @override_settings(
+        INSTALLED_APPS=[
+            "migrations.migrations_test_apps.migrated_app",
+            "migrations.migrations_test_apps.conflicting_app_with_dependencies"])
+    def test_makemigrations_merge_dont_output_dependency_operations(self):
+        """
+        Makes sure that makemigrations --merge does not output any operations
+        from apps that don't belong to a given app.
+        """
+        # Monkeypatch interactive questioner to auto accept
+        with mock.patch('django.db.migrations.questioner.input', mock.Mock(return_value='N')):
+            out = six.StringIO()
+            with mock.patch('django.core.management.color.supports_color', lambda *args: False):
+                call_command(
+                    "makemigrations", "conflicting_app_with_dependencies",
+                    merge=True, interactive=True, stdout=out
+                )
+            val = out.getvalue().lower()
+            self.assertIn('merging conflicting_app_with_dependencies\n', val)
+            self.assertIn(
+                '  branch 0002_conflicting_second\n'
+                '    - create model something\n',
+                val
+            )
+            self.assertIn(
+                '  branch 0002_second\n'
+                '    - delete model tribble\n'
+                '    - remove field silly_field from author\n'
+                '    - add field rating to author\n'
+                '    - create model book\n',
+                val
+            )
+
     def test_makemigrations_with_custom_name(self):
         """
         Makes sure that makemigrations generate a custom migration.