Allow overriding language_code field in translation models. Closes KristianOellegaard#332.

Author: spectras

docs/public/models.rst

@@ -23,8 +23,8 @@ regular Django, with the following additional features:
 - Translatable fields can be used in the model options. For options that take
   groupings of fields (``unique_together`` and ``index_together``), each grouping
   may have either translatable or non-translatable fields, but not both.
-- Special field ``language_code`` may be used for defining ``unique_together``
-  constraints that are only unique per language.
+- Special field ``language_code`` is automatically created by hvad, and may be used
+  for defining ``unique_together`` constraints that are only unique per language.
 
 A full example of a model with translations::
 
@@ -44,6 +44,10 @@ A full example of a model with translations::
 
 .. note:: The :djterm:`Meta <meta-options>` class of the model may not use the
           translatable fields in :attr:`~django.db.models.Options.order_with_respect_to`.
+.. note:: TranslatedFields cannot contain a field named ``master``, as this name
+          is reserved by hvad to refer to the :term:`Shared Model`. Also, special
+          field ``language_code`` can be overriden in order to set it to be a
+          different type of field, or change its options.
 
 ***********************
 New and Changed Methods

docs/public/release_notes.rst

@@ -27,6 +27,8 @@ New features:
   See the section about
   :ref:`overriding the default queryset <override-default-queryset>`
   for advantages and caveats of doing so.
+- Field declaration for internal ``language_code`` attribute can be overriden.
+  — :issue:`332`.
 
 Compatibility warnings:
 
@@ -53,6 +55,9 @@ Fixes:
 
 - Increase speed of translated attribute access by ~30%, by avoiding a method call
   when a translation is loaded.
+- Attempting to use a reserved name for a translated field now raises an
+  :exc:`~django.core.exceptions.ImproperlyConfigured` exception instead of silently
+  ignoring the field.
 
 *****************************
 1.7.0 - current release

hvad/models.py

@@ -18,12 +18,18 @@
 
 __all__ = ('TranslatableModel', 'TranslatedFields', 'NoTranslation')
 
+forbidden_translated_fields = frozenset({'Meta', 'objects', 'master', 'master_id'})
+
 #===============================================================================
 
 class TranslatedFields(object):
     """ Wrapper class to define translated fields on a model. """
 
     def __init__(self, meta=None, base_class=None, **fields):
+        forbidden = forbidden_translated_fields.intersection(fields)
+        if forbidden:
+            raise ImproperlyConfigured(
+                'Invalid translated field: %s' % ', '.join(sorted(forbidden)))
         self.meta = meta or {}
         self.base_class = base_class
         self.fields = fields
@@ -76,14 +82,12 @@ def create_translations_model(self, model, related_name):
         })
 
         if not model._meta.abstract:
-            attrs.update({
-                # If this class is abstract, we must not contribute management fields
-                'objects': TranslationsModelManager(),
-                'language_code': models.CharField(max_length=15, db_index=True),
-                # Nullable so we can prevent cascade deletion
-                'master': models.ForeignKey(model, related_name=related_name, editable=False,
-                                            on_delete=models.CASCADE),
-            })
+            # If this class is abstract, we must not contribute management fields
+            attrs['objects'] = TranslationsModelManager()
+            attrs['master'] = models.ForeignKey(model, related_name=related_name,
+                                                editable=False, on_delete=models.CASCADE)
+            if 'language_code' not in attrs:    # allow overriding
+                attrs['language_code'] = models.CharField(max_length=15, db_index=True)
 
         # Create the new model
         if self.base_class:

hvad/tests/basic.py

@@ -262,6 +262,16 @@ def test_manager_properties(self):
         manager = Normal.objects
         self.assertEqual(manager.translations_model, Normal._meta.translations_model)
 
+    def test_language_code_override(self):
+        class LanguageCodeOverrideModel(TranslatableModel):
+            translations = TranslatedFields(
+                tfield=models.CharField(max_length=250),
+                language_code=models.UUIDField(editable=False, db_index=True),
+            )
+        tmodel = LanguageCodeOverrideModel._meta.translations_model
+        self.assertIsInstance(tmodel._meta.get_field('language_code'), models.UUIDField)
+
+
 class OptionsTest(HvadTestCase):
     def test_options(self):
         self.assertEqual(Normal._meta.translations_model.__name__, 'NormalTranslation')