Use 'unkown' as fallback name if the verbose_name exclusively contains unslugifiable chars.

Author: gregmuellegger

readthedocs/builds/version_slug.py

@@ -41,8 +41,10 @@ class VersionSlugField(models.CharField):
     Implementation inspired by ``django_extensions.db.fields.AutoSlugField``.
     """
 
-    allowed_chars = string.lowercase + string.digits + '-._'
+    allowed_punctuation = '-._'
+    allowed_chars = string.lowercase + string.digits + allowed_punctuation
     placeholder = '-'
+    fallback_slug = 'unkown'
 
     def __init__(self, *args, **kwargs):
         kwargs.setdefault('db_index', True)
@@ -70,6 +72,18 @@ def slugify(self, content):
                 slugified += self.placeholder
             else:
                 slugified += char
+
+        # Do not start and end in punctuation.
+        slug_length = len(slugified)
+        diff = 1
+        while diff > 0:
+            for char in self.allowed_punctuation:
+                slugified = slugified.strip(char)
+            diff = slug_length - len(slugified)
+            slug_length = len(slugified)
+
+        if not slugified:
+            return self.fallback_slug
         return slugified
 
     def uniquifying_suffix(self, iteration):

readthedocs/rtd_tests/tests/test_version_slug.py

@@ -35,6 +35,23 @@ def test_uppercase(self):
             project=self.pip)
         self.assertEqual(version.slug, 'somestring-charclass')
 
+    def test_placeholder_as_name(self):
+        version = Version.objects.create(
+            verbose_name='-',
+            project=self.pip)
+        self.assertEqual(version.slug, 'unkown')
+
+    def test_multiple_empty_names(self):
+        version = Version.objects.create(
+            verbose_name='-',
+            project=self.pip)
+        self.assertEqual(version.slug, 'unkown')
+
+        version = Version.objects.create(
+            verbose_name='-./.-',
+            project=self.pip)
+        self.assertEqual(version.slug, 'unkown_a')
+
     def test_uniqueness(self):
         version = Version.objects.create(
             verbose_name='1!0',