[1.8.x] Fixed #24278 -- Fixed serialization of migration operations.

Fixed MigrationWriter.serialize() to correctly handle migration
operations by utilizing OperationWriter.

Thanks Piotr Maliński for the report.

Backport of e8e4f978dd4b7a3d0c689c6e3301e3c6f9e50003 from master

1 files changed, 44 insertions, 0 deletions

diff --git a/tests/migrations/test_writer.py b/tests/migrations/test_writer.py
index b60d6e79da..a6527caea4 100644
--- a/tests/migrations/test_writer.py
+++ b/tests/migrations/test_writer.py
@@ -81,6 +81,27 @@ class OperationWriterTests(SimpleTestCase):
             '),'
         )
 
+    def test_nested_args_signature(self):
+        operation = custom_migration_operations.operations.ArgsOperation(
+            custom_migration_operations.operations.ArgsOperation(1, 2),
+            custom_migration_operations.operations.KwargsOperation(kwarg1=3, kwarg2=4)
+        )
+        buff, imports = OperationWriter(operation, indentation=0).serialize()
+        self.assertEqual(imports, {'import custom_migration_operations.operations'})
+        self.assertEqual(
+            buff,
+            'custom_migration_operations.operations.ArgsOperation(\n'
+            '    arg1=custom_migration_operations.operations.ArgsOperation(\n'
+            '        arg1=1,\n'
+            '        arg2=2,\n'
+            '    ),\n'
+            '    arg2=custom_migration_operations.operations.KwargsOperation(\n'
+            '        kwarg1=3,\n'
+            '        kwarg2=4,\n'
+            '    ),\n'
+            '),'
+        )
+
     def test_multiline_args_signature(self):
         operation = custom_migration_operations.operations.ArgsOperation("test\n    arg1", "test\narg2")
         buff, imports = OperationWriter(operation, indentation=0).serialize()
@@ -107,6 +128,29 @@ class OperationWriterTests(SimpleTestCase):
             '),'
         )
 
+    def test_nested_operation_expand_args_signature(self):
+        operation = custom_migration_operations.operations.ExpandArgsOperation(
+            arg=[
+                custom_migration_operations.operations.KwargsOperation(
+                    kwarg1=1,
+                    kwarg2=2,
+                ),
+            ]
+        )
+        buff, imports = OperationWriter(operation, indentation=0).serialize()
+        self.assertEqual(imports, {'import custom_migration_operations.operations'})
+        self.assertEqual(
+            buff,
+            'custom_migration_operations.operations.ExpandArgsOperation(\n'
+            '    arg=[\n'
+            '        custom_migration_operations.operations.KwargsOperation(\n'
+            '            kwarg1=1,\n'
+            '            kwarg2=2,\n'
+            '        ),\n'
+            '    ],\n'
+            '),'
+        )
+
 
 class WriterTests(TestCase):
     """