Fixed #22788 -- Ensured custom migration operations can be written.

This inspects the migration operation, and if it is not in the
django.db.migrations module, it adds the relevant imports to the
migration writer and uses the correct class name.

4 files changed, 70 insertions, 0 deletions

diff --git a/tests/custom_migration_operations/__init__.py b/tests/custom_migration_operations/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/custom_migration_operations/__init__.py
diff --git a/tests/custom_migration_operations/more_operations.py b/tests/custom_migration_operations/more_operations.py
new file mode 100644
index 0000000000..6fe3d1cf93
--- /dev/null
+++ b/tests/custom_migration_operations/more_operations.py
@@ -0,0 +1,22 @@
+from django.db.migrations.operations.base import Operation
+
+
+class TestOperation(Operation):
+    def __init__(self):
+        pass
+
+    @property
+    def reversible(self):
+        return True
+
+    def state_forwards(self, app_label, state):
+        pass
+
+    def database_forwards(self, app_label, schema_editor, from_state, to_state):
+        pass
+
+    def state_backwards(self, app_label, state):
+        pass
+
+    def database_backwards(self, app_label, schema_editor, from_state, to_state):
+        pass
diff --git a/tests/custom_migration_operations/operations.py b/tests/custom_migration_operations/operations.py
new file mode 100644
index 0000000000..fc084f8412
--- /dev/null
+++ b/tests/custom_migration_operations/operations.py
@@ -0,0 +1,26 @@
+from django.db.migrations.operations.base import Operation
+
+
+class TestOperation(Operation):
+    def __init__(self):
+        pass
+
+    @property
+    def reversible(self):
+        return True
+
+    def state_forwards(self, app_label, state):
+        pass
+
+    def database_forwards(self, app_label, schema_editor, from_state, to_state):
+        pass
+
+    def state_backwards(self, app_label, state):
+        pass
+
+    def database_backwards(self, app_label, schema_editor, from_state, to_state):
+        pass
+
+
+class CreateModel(TestOperation):
+    pass
diff --git a/tests/migrations/test_writer.py b/tests/migrations/test_writer.py
index 925a9d6538..cd59938314 100644
--- a/tests/migrations/test_writer.py
+++ b/tests/migrations/test_writer.py
@@ -16,6 +16,9 @@ from django.utils.deconstruct import deconstructible
 from django.utils.translation import ugettext_lazy as _
 from django.utils.timezone import get_default_timezone
 
+import custom_migration_operations.operations
+import custom_migration_operations.more_operations
+
 
 class TestModel1(object):
     def upload_to(self):
@@ -222,3 +225,22 @@ class WriterTests(TestCase):
                 expected_path = os.path.join(base_dir, *(app.split('.') + ['migrations', '0001_initial.py']))
                 writer = MigrationWriter(migration)
                 self.assertEqual(writer.path, expected_path)
+
+    def test_custom_operation(self):
+        migration = type(str("Migration"), (migrations.Migration,), {
+            "operations": [
+                custom_migration_operations.operations.TestOperation(),
+                custom_migration_operations.operations.CreateModel(),
+                migrations.CreateModel("MyModel", (), {}, (models.Model,)),
+                custom_migration_operations.more_operations.TestOperation()
+            ],
+            "dependencies": []
+        })
+        writer = MigrationWriter(migration)
+        output = writer.as_string()
+        result = self.safe_exec(output)
+        self.assertIn("custom_migration_operations", result)
+        self.assertNotEqual(
+            result['custom_migration_operations'].operations.TestOperation,
+            result['custom_migration_operations'].more_operations.TestOperation
+        )