Add a new auto-slug field that is concurrency resistent

localized_fields/db_backend/base.py

@@ -5,6 +5,8 @@ from django.core.exceptions import ImproperlyConfigured
 from django.db.backends.postgresql.base import \
     DatabaseWrapper as Psycopg2DatabaseWrapper
 
+from ..fields import LocalizedField
+
 
 def _get_backend_base():
     """Gets the base class for the custom database back-end.
@@ -153,7 +155,22 @@ class SchemaEditor(_get_schema_editor_base()):
             *args, **kwargs
         )
 
-        self._update_hstore_constraints(model, old_field, new_field)
+        is_old_field_localized = isinstance(old_field, LocalizedField)
+        is_new_field_localized = isinstance(new_field, LocalizedField)
+
+        if is_old_field_localized or is_new_field_localized:
+            self._update_hstore_constraints(model, old_field, new_field)
+
+    def create_model(self, model):
+        """Ran when a new model is created."""
+
+        super().create_model(model)
+
+        for field in model._meta.local_fields:
+            if not isinstance(field, LocalizedField):
+                continue
+
+            self._update_hstore_constraints(model, field, field)
 
 
 class DatabaseWrapper(_get_backend_base()):

localized_fields/fields/localized_magicslug_field.py

@@ -59,6 +59,9 @@ class LocalizedMagicSlugField(LocalizedAutoSlugField):
                 continue
 
             slug = slugify(value, allow_unicode=True)
+            if instance.retries > 0:
+                slug += '-%d' % instance.retries
+
             slugs.set(lang_code, slug)
 
         setattr(instance, self.name, slugs)

localized_fields/models.py

@@ -1,4 +1,6 @@
 from django.db import models
+from django.db.utils import IntegrityError
+from django.db import transaction
 
 from .fields import LocalizedField
 from .localized_value import LocalizedValue
@@ -32,3 +34,30 @@ class LocalizedModel(models.Model):
                     value = LocalizedValue()
 
             setattr(self, field.name, value)
+
+    def save(self, *args, **kwargs):
+        """Saves this model instance to the database."""
+
+        if not hasattr(self, 'retries'):
+            self.retries = 0
+
+        error = None
+        with transaction.atomic():
+            try:
+                return super(LocalizedModel, self).save(*args, **kwargs)
+            except IntegrityError as ex:
+                # this is as retarded as it looks, there's no
+                # way we can put the retry logic inside the slug
+                # field class... we can also not only catch exceptions
+                # that apply to slug fields... so yea.. this is as
+                # retarded as it gets... i am sorry :(
+                if 'slug' not in str(ex):
+                    raise ex
+
+                error = ex
+
+        if self.retries >= 100:
+            raise error
+
+        self.retries += 1
+        return self.save()

settings.py

@@ -3,7 +3,7 @@ import dj_database_url
 DEBUG = True
 TEMPLATE_DEBUG = True
 
-SECRET_KEY = 'this is my secret key'
+SECRET_KEY = 'this is my secret key'  # NOQA
 
 TEST_RUNNER = 'django.test.runner.DiscoverRunner'
 
@@ -11,6 +11,8 @@ DATABASES = {
     'default': dj_database_url.config(default='postgres:///localized_fields')
 }
 
+DATABASES['default']['ENGINE'] = 'localized_fields.db_backend'
+
 LANGUAGE_CODE = 'en'
 LANGUAGES = (
     ('en', 'English'),

tests/fake_model.py

@@ -1,10 +1,7 @@
-from django.contrib.postgres.operations import HStoreExtension
 from django.db import connection, migrations
+from localized_fields import LocalizedModel
 from django.db.migrations.executor import MigrationExecutor
-import sys
-
-from localized_fields import (LocalizedAutoSlugField, LocalizedField,
-                              LocalizedModel, LocalizedMagicSlugField)
+from django.contrib.postgres.operations import HStoreExtension
 
 
 def get_fake_model(name='TestModel', fields={}):

tests/test_localized_slug_fields.py

@@ -1,10 +1,10 @@
 from django import forms
 from django.conf import settings
 from django.test import TestCase
+from localized_fields import (LocalizedField, LocalizedAutoSlugField,
+                              LocalizedMagicSlugField)
 from django.utils.text import slugify
 
-from localized_fields import LocalizedField, LocalizedAutoSlugField, LocalizedMagicSlugField
-
 from .fake_model import get_fake_model
 
 
@@ -71,7 +71,6 @@ class LocalizedSlugFieldTestCase(TestCase):
     @classmethod
     def test_deconstruct_auto(cls):
         cls._test_deconstruct(LocalizedAutoSlugField)
-        cls._test_deconstruct(LocalizedMagicSlugField)
 
     @classmethod
     def test_deconstruct_magic(cls):
@@ -93,7 +92,7 @@ class LocalizedSlugFieldTestCase(TestCase):
         obj.title.en = 'this is my title'
         obj.save()
 
-        assert obj.slug.get('en') == slugify(obj.title.en)
+        assert obj.slug.get('en') == slugify(obj.title)
 
     @staticmethod
     def _test_populate_multiple_languages(model):
@@ -117,11 +116,12 @@ class LocalizedSlugFieldTestCase(TestCase):
         obj.title.en = 'title'
         obj.save()
 
-        another_obj = model()
-        another_obj.title.en = 'title'
-        another_obj.save()
+        for i in range(1, 90):
+            another_obj = model()
+            another_obj.title.en = 'title'
+            another_obj.save()
 
-        assert another_obj.slug.en == 'title-1'
+            assert another_obj.slug.en == 'title-%d' % i
 
     @staticmethod
     def _test_unique_slug_utf(model):