generate slug from title and chomp off enough space

for the counter suffix when handling collisions.
handles pyvideo#249

src/richard/videos/utils.py

@@ -19,18 +19,18 @@
 
 
 def generate_unique_slug(obj, slug_from, slug_field='slug'):
-    text = getattr(obj, slug_from)[:49]
-    root_text = text
+    """ generate slug with trailing counts to prevent name collision """
+
+    max_length = obj._meta.get_field(slug_field).max_length
+
+    text = getattr(obj, slug_from)[:max_length]
+    base_slug = slugify(text_type(text))
+    slug = base_slug
+
     for i in range(100):
-        slug = slugify(text_type(text))
-        try:
-            d = {slug_field: slug}
-            obj.__class__.objects.get(**d)
-        except obj.__class__.DoesNotExist:
+        if not obj.__class__.objects.filter(**{slug_field: slug}).exists():
             return slug
-
-        ending = u'-%s' % i
-        text = root_text + ending
+        suffix = text_type(i)
+        slug = u'{}-{}'.format(base_slug[:max_length - len(suffix) - 1], suffix)
 
     raise ValueError('No valid slugs available.')
-

tests/test_videos/test_api.py

@@ -271,7 +271,7 @@ def test_post_video(self):
 
         vid = Video.objects.get(title=data['title'])
         assert vid.title == data['title']
-        assert vid.slug == u'creating-delicious-apis-for-django-apps-since-201'
+        assert vid.slug == u'creating-delicious-apis-for-django-apps-since-2010'
         assert list(vid.speakers.values_list('name', flat=True)) == ['Guido']
         assert (
             sorted(vid.tags.values_list('tag', flat=True)) ==

tests/test_videos/test_utils.py

@@ -16,6 +16,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from django.test import TestCase
+import pytest
 
 from . import factories
 from richard.videos.utils import generate_unique_slug
@@ -32,8 +33,10 @@ def test_slug_creation(self):
 
     def test_unique_slug(self):
         """Generate unique slug using incrementing ending."""
-        # These all have the same title, so they get increasingly
-        # lame slugs.
+        # These all have the same title, so subsequent videos get
+        # a trailing count on the slug
+
+        # This title is short! We want to check this so we don't chomp everything
         factories.VideoFactory.create_batch(title=u'Foo', size=5)
 
         v2 = factories.VideoFactory.build(title=u'Foo')
@@ -42,6 +45,19 @@ def test_unique_slug(self):
             u'foo-4'
         )
 
+    def test_max_length_slug(self):
+        # this is 51 characters long! We want to make sure we don't barf on lengthy titles
+        title = u'Creating delicious APIs for Django apps since 2010.'
+        factories.VideoFactory.create_batch(title=title, size=99)
+
+        v2 = factories.VideoFactory.create(title=title)
+        assert (
+            v2.slug == u'creating-delicious-apis-for-django-apps-since-2-98'
+        )
+        # now that we've created 100 duplicates, we've run out of slugs.
+        with pytest.raises(ValueError):
+            factories.VideoFactory.create(title=title)
+
     def test_unicode_title(self):
         v = factories.VideoFactory.build(title=u'Nebenläufige Programme mit Python')
         assert (