Add a flag to make LocalizedUniqueSlugField immutable

localized_fields/fields/uniqueslug_field.py

@@ -21,13 +21,19 @@ class LocalizedUniqueSlugField(LocalizedAutoSlugField):
     When in doubt, use this over :see:LocalizedAutoSlugField.
     Inherit from :see:AtomicSlugRetryMixin in your model to
     make this field work properly.
+
+    By default, this creates a new slug if the field(s) specified
+    in `populate_from` are changed. Set `immutable=True` to get
+    immutable slugs.
     """
 
     def __init__(self, *args, **kwargs):
         """Initializes a new instance of :see:LocalizedUniqueSlugField."""
 
         kwargs["uniqueness"] = kwargs.pop("uniqueness", get_language_codes())
 
+        self.immutable = kwargs.pop("immutable", False)
+
         super(LocalizedUniqueSlugField, self).__init__(*args, **kwargs)
 
         self.populate_from = kwargs.pop("populate_from")
@@ -42,6 +48,10 @@ def deconstruct(self):
 
         kwargs["populate_from"] = self.populate_from
         kwargs["include_time"] = self.include_time
+
+        if self.immutable is True:
+            kwargs["immutable"] = self.immutable
+
         return name, path, args, kwargs
 
     def pre_save(self, instance, add: bool):
@@ -76,10 +86,14 @@ def pre_save(self, instance, add: bool):
 
             slug = slugify(value, allow_unicode=True)
 
+            current_slug = getattr(instance, self.name).get(lang_code)
+            if current_slug and self.immutable:
+                slugs.set(lang_code, current_slug)
+                continue
+
             # 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:
                     current_slug_end_index = current_slug.rfind("-")
                     stripped_slug = current_slug[0:current_slug_end_index]

tests/test_slug_fields.py

@@ -215,6 +215,32 @@ def test_populate_multiple_languages(cls):
         for lang_code, lang_name in settings.LANGUAGES:
             assert obj.slug.get(lang_code) == "title-%s" % lang_name.lower()
 
+    @classmethod
+    def test_allows_override_when_immutable(cls):
+        """Tests whether setting a value manually works and does not get
+        overriden."""
+
+        Model = get_fake_model(
+            {
+                "title": LocalizedField(),
+                "name": models.CharField(max_length=255),
+                "slug": LocalizedUniqueSlugField(
+                    populate_from="title", immutable=True
+                ),
+            }
+        )
+
+        obj = Model()
+
+        for lang_code, lang_name in settings.LANGUAGES:
+            obj.slug.set(lang_code, "my value %s" % lang_code)
+            obj.title.set(lang_code, "my title %s" % lang_code)
+
+        obj.save()
+
+        for lang_code, lang_name in settings.LANGUAGES:
+            assert obj.slug.get(lang_code) == "my value %s" % lang_code
+
     @classmethod
     def test_unique_slug(cls):
         """Tests whether unique slugs are properly generated."""