[1.8.x] Fixed #24427 -- Stopped writing migration files in dry run mode when merging.

Also added display of migration to stdout when verbosity=3.

Backport of 8758a63ddbbf7a2626bd84d50cfe83b477e8de0a from master

1 files changed, 43 insertions, 0 deletions

diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index f97ba05cb0..c8cf814e43 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -582,6 +582,49 @@ class MakeMigrationsTests(MigrationTestBase):
         self.assertFalse(os.path.exists(merge_file))
         self.assertIn("Created new merge migration", output)
 
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_conflict"})
+    def test_makemigration_merge_dry_run(self):
+        """
+        Makes sure that makemigrations respects --dry-run option when fixing
+        migration conflicts (#24427).
+        """
+        out = six.StringIO()
+        call_command("makemigrations", "migrations", dry_run=True, merge=True, interactive=False, stdout=out)
+        merge_file = os.path.join(self.test_dir, '0003_merge.py')
+        self.assertFalse(os.path.exists(merge_file))
+        output = force_text(out.getvalue())
+        self.assertIn("Merging migrations", output)
+        self.assertIn("Branch 0002_second", output)
+        self.assertIn("Branch 0002_conflicting_second", output)
+        self.assertNotIn("Created new merge migration", output)
+
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_conflict"})
+    def test_makemigration_merge_dry_run_verbosity_3(self):
+        """
+        Makes sure that `makemigrations --merge --dry-run` writes the merge
+        migration file to stdout with `verbosity == 3` (#24427).
+        """
+        out = six.StringIO()
+        call_command("makemigrations", "migrations", dry_run=True, merge=True, interactive=False,
+                     stdout=out, verbosity=3)
+        merge_file = os.path.join(self.test_dir, '0003_merge.py')
+        self.assertFalse(os.path.exists(merge_file))
+        output = force_text(out.getvalue())
+        self.assertIn("Merging migrations", output)
+        self.assertIn("Branch 0002_second", output)
+        self.assertIn("Branch 0002_conflicting_second", output)
+        self.assertNotIn("Created new merge migration", output)
+
+        # Additional output caused by verbosity 3
+        # The complete merge migration file that would be written
+        self.assertIn("# -*- coding: utf-8 -*-", output)
+        self.assertIn("class Migration(migrations.Migration):", output)
+        self.assertIn("dependencies = [", output)
+        self.assertIn("('migrations', '0002_second')", output)
+        self.assertIn("('migrations', '0002_conflicting_second')", output)
+        self.assertIn("operations = [", output)
+        self.assertIn("]", output)
+
     @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_no_default"})
     def test_makemigrations_dry_run(self):
         """