validate slugs on model save

- prevent generation of tag with non-unique slug
- prevent generation of tag with name containing
  only invalid characters

Author: chris48s

project/resources/migrations/0006_auto_20200303_1257.py

@@ -8,7 +8,7 @@ class Migration(migrations.Migration):
 
     dependencies = [
         ('resources', '0005_auto_20200118_1036'),
-        ('tagging', '__latest__')
+        ('tagging', '0001_initial')
     ]
 
     operations = [

project/tagging/migrations/0002_auto_20200405_0312.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.4 on 2020-04-05 10:12
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tagging', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='customtag',
+            name='slug',
+            field=models.SlugField(allow_unicode=True, max_length=100, unique=True, verbose_name='Slug'),
+        ),
+    ]

project/tagging/models.py

@@ -8,7 +8,12 @@
 
 class CustomTag(TagBase):
     guid = models.UUIDField(default=uuid.uuid1, editable=False)
-    slug = models.SlugField(verbose_name=_("Slug"), unique=True, max_length=100)
+    slug = models.SlugField(
+        verbose_name=_("Slug"),
+        unique=True,
+        max_length=100,
+        allow_unicode=True
+    )
     name = models.CharField(verbose_name=_("Name"), unique=True, max_length=100)
 
     class Meta:
@@ -17,15 +22,13 @@ class Meta:
         verbose_name_plural = _("Tags")
         app_label = 'tagging'
 
+    def save(self, *args, **kwargs):
+        self.slug = self.slugify(self.name)
+        self.full_clean()
+        return super().save(*args, **kwargs)
 
     def slugify(self, tag, i=None):
-        slug = slugify(tag, allow_unicode=True)
-
-        if i is not None:
-            slug += "_%d" % i
-
-        return slug
-
+        return slugify(tag, allow_unicode=True)
 
 class TaggedItems(GenericTaggedItemBase, TaggedItemBase):
     tag = models.ForeignKey(CustomTag,

project/tagging/tests.py

@@ -1,9 +1,10 @@
+from django.core.exceptions import ValidationError
 from django.test import TestCase
 from .models import CustomTag
 
 
 class CustomTagTests(TestCase):
-    def test_slugging(self):
+    def test_valid_slugs(self):
         test_tags = [
             {"name": "programming", "expected_slug": "programming"},
             {"name": "PyCon", "expected_slug": "pycon"},
@@ -33,12 +34,34 @@ def test_slugging(self):
             {"name": "प्रयास है", "expected_slug": "परयस-ह"},
             {"name": "stòran-dàta", "expected_slug": "stòran-dàta"},
             {"name": "స్వయంచాలక", "expected_slug": "సవయచలక"},
-
-            {"name": "❤", "expected_slug": ""},
-            {"name": "🐸", "expected_slug": "_1"},
         ]
 
         for entry in test_tags:
             tag = CustomTag(name=entry["name"])
             tag.save()
             self.assertEqual(tag.slug, entry["expected_slug"])
+
+    def test_invalid_slugs(self):
+        invalid_tag_names = [
+            "❤🐸",
+            "🐸",
+            "  %",
+            "//",
+        ]
+        for name in invalid_tag_names:
+            with self.assertRaises(ValidationError):
+                tag = CustomTag(name=name)
+                tag.save()
+
+    def test_duplicates(self):
+        tag1 = CustomTag(name='javascript')
+        tag1.save()
+
+        # fail if we try to generate more tags with the same slug
+        with self.assertRaises(ValidationError):
+            tag2 = CustomTag(name='Javascript')
+            tag2.save()
+
+        with self.assertRaises(ValidationError):
+            tag3 = CustomTag(name='JaVascripT%/')
+            tag3.save()