Started work on LocalizedMagicSlugField

This will be a superior version of LocalizedAutoSlugField, but one
that doesn't have concurrency issues and takes advantage of the
new UNIQUE CONSTRAINTs.

localized_fields/__init__.py

@@ -1,7 +1,7 @@
 from .util import get_language_codes
 from .forms import LocalizedFieldForm, LocalizedFieldWidget
 from .fields import (LocalizedField, LocalizedBleachField,
-                     LocalizedAutoSlugField)
+                     LocalizedAutoSlugField, LocalizedMagicSlugField)
 from .localized_value import LocalizedValue
 from .models import LocalizedModel
 
@@ -10,6 +10,7 @@ __all__ = [
     'LocalizedField',
     'LocalizedValue',
     'LocalizedAutoSlugField',
+    'LocalizedMagicSlugField',
     'LocalizedBleachField',
     'LocalizedFieldWidget',
     'LocalizedFieldForm',

localized_fields/fields/__init__.py

@@ -1,10 +1,12 @@
 from .localized_field import LocalizedField
 from .localized_autoslug_field import LocalizedAutoSlugField
+from .localized_magicslug_field import LocalizedMagicSlugField
 from .localized_bleach_field import LocalizedBleachField
 
 
 __all__ = [
     'LocalizedField',
     'LocalizedAutoSlugField',
-    'LocalizedBleachField'
+    'LocalizedMagicSlugField',
+    'LocalizedBleachField',
 ]

localized_fields/fields/localized_autoslug_field.py

@@ -9,9 +9,8 @@ from ..localized_value import LocalizedValue
 
 
 class LocalizedAutoSlugField(LocalizedField):
-    """Custom version of :see:AutoSlugField that
-    can operate on :see:LocalizedField and provides
-    unique slugs for every language."""
+    """Automatically provides slugs for a localized
+    field upon saving."""
 
     def __init__(self, *args, **kwargs):
         """Initializes a new instance of :see:LocalizedAutoSlugField."""
@@ -29,8 +28,8 @@ class LocalizedAutoSlugField(LocalizedField):
 
         name, path, args, kwargs = super(
             LocalizedAutoSlugField, self).deconstruct()
-        kwargs['populate_from'] = self.populate_from
 
+        kwargs['populate_from'] = self.populate_from
         return name, path, args, kwargs
 
     def formfield(self, **kwargs):

localized_fields/fields/localized_magicslug_field.py

@@ -0,0 +1,65 @@
+from django.conf import settings
+from django.utils.text import slugify
+
+from ..localized_value import LocalizedValue
+from .localized_autoslug_field import LocalizedAutoSlugField
+from ..util import get_language_codes
+
+
+class LocalizedMagicSlugField(LocalizedAutoSlugField):
+    """Automatically provides slugs for a localized
+    field upon saving."
+
+    An improved version of :see:LocalizedAutoSlugField,
+    which adds:
+
+        - Concurrency safety
+        - Improved performance
+
+    When in doubt, use this over :see:LocalizedAutoSlugField.
+    """
+
+    def __init__(self, *args, **kwargs):
+        """Initializes a new instance of :see:LocalizedMagicSlugField."""
+
+        self.populate_from = kwargs.pop('populate_from')
+        kwargs['uniqueness'] = kwargs.pop('uniqueness', get_language_codes())
+
+        super(LocalizedAutoSlugField, self).__init__(
+            *args,
+            **kwargs
+        )
+
+    def pre_save(self, instance, add: bool):
+        """Ran just before the model is saved, allows us to built
+        the slug.
+
+        Arguments:
+            instance:
+                The model that is being saved.
+
+            add:
+                Indicates whether this is a new entry
+                to the database or an update.
+
+        Returns:
+            The localized slug that was generated.
+        """
+
+        slugs = LocalizedValue()
+
+        for lang_code, _ in settings.LANGUAGES:
+            value = self._get_populate_from_value(
+                instance,
+                self.populate_from,
+                lang_code
+            )
+
+            if not value:
+                continue
+
+            slug = slugify(value, allow_unicode=True)
+            slugs.set(lang_code, slug)
+
+        setattr(instance, self.name, slugs)
+        return slugs