Don't regenerate slug if not needed

localized_fields/fields/localized_uniqueslug_field.py

@@ -1,3 +1,5 @@
+from datetime import datetime
+
 from django.conf import settings
 from django.utils.text import slugify
 from django.core.exceptions import ImproperlyConfigured
@@ -7,8 +9,6 @@ from ..mixins import AtomicSlugRetryMixin
 from ..localized_value import LocalizedValue
 from .localized_autoslug_field import LocalizedAutoSlugField
 
-from datetime import datetime
-
 
 class LocalizedUniqueSlugField(LocalizedAutoSlugField):
     """Automatically provides slugs for a localized
@@ -47,8 +47,6 @@ class LocalizedUniqueSlugField(LocalizedAutoSlugField):
 
         kwargs['populate_from'] = self.populate_from
         kwargs['include_time'] = self.include_time
-        # if not kwargs['include_time']:
-        #     raise RuntimeError()
         return name, path, args, kwargs
 
     def pre_save(self, instance, add: bool):
@@ -86,11 +84,25 @@ class LocalizedUniqueSlugField(LocalizedAutoSlugField):
                 continue
 
             slug = slugify(value, allow_unicode=True)
+
+            # verify whether it's needed to re-generate a slug,
+            # if not, re-use the same slug
+            if instance.pk is not None:
+                current_slug = getattr(instance, self.name).get(lang_code)
+                if current_slug is not None:
+                    stripped_slug = current_slug[0:current_slug.rfind('-')]
+                    if slug == stripped_slug:
+                        slugs.set(lang_code, current_slug)
+                        continue
+
             if self.include_time:
                 slug += '-%d' % datetime.now().microsecond
 
             if instance.retries > 0:
-                slug += '-%d' % instance.retries
+                # do not add another - if we already added time
+                if not self.include_time:
+                    slug += '-'
+                slug += '%d' % instance.retries
 
             slugs.set(lang_code, slug)
 

tests/test_localized_slug_fields.py

@@ -1,11 +1,12 @@
+import copy
+
 from django import forms
 from django.conf import settings
 from django.test import TestCase
 from django.db.utils import IntegrityError
-from django.utils.text import slugify
-
 from localized_fields import (LocalizedField, LocalizedAutoSlugField,
                               LocalizedUniqueSlugField)
+from django.utils.text import slugify
 
 from .fake_model import get_fake_model
 
@@ -83,6 +84,33 @@ class LocalizedSlugFieldTestCase(TestCase):
 
         assert obj.slug.en.startswith('%s-' % title)
 
+    @classmethod
+    def test_uniue_slug_no_change(cls):
+        """Tests whether slugs are not re-generated if not needed."""
+
+        NoChangeSlugModel = get_fake_model(
+            'NoChangeSlugModel',
+            {
+                'title': LocalizedField(),
+                'slug': LocalizedUniqueSlugField(populate_from='title', include_time=True)
+            }
+        )
+
+        title = 'myuniquetitle'
+
+        obj = NoChangeSlugModel()
+        obj.title.en = title
+        obj.title.nl = title
+        obj.save()
+
+        old_slug_en = copy.deepcopy(obj.slug.en)
+        old_slug_nl = copy.deepcopy(obj.slug.nl)
+        obj.title.nl += 'beer'
+        obj.save()
+
+        assert old_slug_en == obj.slug.en
+        assert old_slug_nl != obj.slug.nl
+
     def test_unique_slug_unique_max_retries(self):
         """Tests whether the unique slug implementation doesn't
         try to find a slug forever and gives up after a while."""