make datamigration for non-unique slugs, test the migration

categories/migrations/0004_unique_category_slug.py

@@ -3,13 +3,29 @@
 from django.db import migrations, models
 
 
+def make_slugs_unique(apps, schema_editor):
+    Category = apps.get_model('categories', 'Category')
+    duplicates = Category.tree.values('slug').annotate(slug_count=models.Count('slug')).filter(slug_count__gt=1)
+    for duplicate in duplicates:
+        slug = duplicate['slug']
+        categories = Category.tree.filter(slug=slug)
+        count = categories.count()
+        i = 0
+        for category in categories.all():
+            if i != 0:
+                category.slug = "%s_%s" % (slug, str(i).zfill(len(str(count))))
+                category.save()
+            i += 1
+
+
 class Migration(migrations.Migration):
 
     dependencies = [
         ('categories', '0003_auto_20200306_1050'),
     ]
 
     operations = [
+        migrations.RunPython(make_slugs_unique, reverse_code=migrations.RunPython.noop),
         migrations.AlterField(
             model_name='category',
             name='slug',

categories/tests/test_migrations.py

@@ -0,0 +1,44 @@
+import sys
+
+
+if (sys.version_info >= (3, 0)):
+    from django_test_migrations.contrib.unittest_case import MigratorTestCase
+
+    class TestMigrations(MigratorTestCase):
+
+        migrate_from = ('categories', '0003_auto_20200306_1050')
+        migrate_to = ('categories', '0004_unique_category_slug')
+
+        def prepare(self):
+            Category = self.old_state.apps.get_model('categories', 'Category')
+            Category.tree.create(slug='foo', lft=0, rght=0, tree_id=0, level=0)
+            Category.tree.create(slug='foo', lft=0, rght=0, tree_id=0, level=0)
+            Category.tree.create(slug='foo', lft=0, rght=0, tree_id=0, level=0)
+            for i in range(1, 12):
+                Category.tree.create(slug='bar', lft=0, rght=0, tree_id=0, level=0)
+            Category.tree.create(slug='baz', lft=0, rght=0, tree_id=0, level=0)
+            assert Category.tree.count() == 15
+
+        def test_unique_slug_migration(self):
+            Category = self.new_state.apps.get_model('categories', 'Category')
+
+            self.assertListEqual(
+                list(Category.tree.values_list('slug', flat=True)),
+                [
+                    'foo',
+                    'foo_1',
+                    'foo_2',
+                    'bar',
+                    'bar_01',
+                    'bar_02',
+                    'bar_03',
+                    'bar_04',
+                    'bar_05',
+                    'bar_06',
+                    'bar_07',
+                    'bar_08',
+                    'bar_09',
+                    'bar_10',
+                    'baz',
+                ],
+            )

tox.ini

@@ -16,6 +16,7 @@ deps=
     coverage
     pillow
     ipdb
+    !py27: django-test-migrations
     -r{toxinidir}/requirements.txt
 
 commands=