add fallback_languages_per_field to TranslationOptions

Author: wtayyeb

modeltranslation/translator.py

@@ -475,23 +475,26 @@ def _register_single_model(self, model, opts):
 
         # Substitute original field with descriptor
         model_fallback_languages = getattr(opts, 'fallback_languages', None)
+        model_fallback_languages_per_field = getattr(opts, 'fallback_languages_per_field', {})
         model_fallback_values = getattr(opts, 'fallback_values', NONE)
         model_fallback_undefined = getattr(opts, 'fallback_undefined', NONE)
         for field_name in opts.local_fields.keys():
             field = model._meta.get_field(field_name)
             field_fallback_value = parse_field(model_fallback_values, field_name, NONE)
             field_fallback_undefined = parse_field(model_fallback_undefined, field_name, NONE)
+            field_fallback_language = \
+                model_fallback_languages_per_field.get(field_name, model_fallback_languages)
             descriptor = TranslationFieldDescriptor(
                 field,
-                fallback_languages=model_fallback_languages,
+                fallback_languages=field_fallback_language,
                 fallback_value=field_fallback_value,
                 fallback_undefined=field_fallback_undefined)
             setattr(model, field_name, descriptor)
             if isinstance(field, ForeignKey):
                 # We need to use a special descriptor so that
                 # _id fields on translated ForeignKeys work
                 # as expected.
-                desc = TranslatedRelationIdDescriptor(field_name, model_fallback_languages)
+                desc = TranslatedRelationIdDescriptor(field_name, field_fallback_language)
                 setattr(model, field.get_attname(), desc)
 
                 # Set related field names on other model