Merge pull request #152 from wrwrwr/feature/fallbacks-toggle

Fallbacks toggle

docs/modeltranslation/usage.rst

@@ -246,6 +246,11 @@ What is more, fallback languages order can be overridden per model, using ``Tran
 
 Dict syntax is only allowed there.
 
+Even more, all fallbacks may be switched on or off for just some exceptional block of code using::
+
+    with fallbacks(False):
+        # Work with values for the active language only
+
 Fallback values
 ***************
 

modeltranslation/fields.py

@@ -156,7 +156,7 @@ class TranslationFieldDescriptor(object):
             # Here we check only for None and '', because e.g. 0 should not fall back.
             if val is not None and val != '':
                 return val
-        if self.fallback_value is None:
+        if self.fallback_value is None or not mt_settings.ENABLE_FALLBACKS:
             return self.field.get_default()
         else:
             return self.fallback_value

modeltranslation/settings.py

@@ -51,3 +51,4 @@ for key, value in FALLBACK_LANGUAGES.iteritems():
         if lang not in AVAILABLE_LANGUAGES:
             raise ImproperlyConfigured(
                 'MODELTRANSLATION_FALLBACK_LANGUAGES: "%s" not in LANGUAGES setting.' % lang)
+ENABLE_FALLBACKS = getattr(settings, 'MODELTRANSLATION_ENABLE_FALLBACKS', True)

modeltranslation/tests/__init__.py

@@ -28,7 +28,7 @@ from modeltranslation.tests.translation import (FallbackModel2TranslationOptions
                                                 FieldInheritanceETranslationOptions)
 from modeltranslation.tests.test_settings import TEST_SETTINGS
 from modeltranslation.utils import (build_css_class, build_localized_fieldname,
-                                    auto_populate)
+                                    auto_populate, fallbacks)
 
 try:
     from django.test.utils import override_settings
@@ -512,6 +512,22 @@ class FallbackTests(ModeltranslationTestBase):
             n.title_en = None
             self.assertEqual(n.title, '')  # if all fallbacks fail, return field.get_default()
 
+    def test_fallbacks_toggle(self):
+        with reload_override_settings(MODELTRANSLATION_FALLBACK_LANGUAGES=self.test_fallback):
+            m = models.TestModel(title='foo')
+            with fallbacks(True):
+                self.assertEqual(m.title_de, 'foo')
+                self.assertEqual(m.title_en, None)
+                self.assertEqual(m.title, 'foo')
+                with override('en'):
+                    self.assertEqual(m.title, 'foo')
+            with fallbacks(False):
+                self.assertEqual(m.title_de, 'foo')
+                self.assertEqual(m.title_en, None)
+                self.assertEqual(m.title, 'foo')
+                with override('en'):
+                    self.assertEqual(m.title, '')  # '' is the default
+
 
 class FileFieldsTest(ModeltranslationTestBase):
 

modeltranslation/utils.py

@@ -90,6 +90,8 @@ def resolution_order(lang, override=None):
     First is always the parameter language, later are fallback languages.
     Override parameter has priority over FALLBACK_LANGUAGES.
     """
+    if not settings.ENABLE_FALLBACKS:
+        return (lang,)
     if override is None:
         override = {}
     fallback_for_lang = override.get(lang, settings.FALLBACK_LANGUAGES.get(lang, ()))
@@ -123,3 +125,25 @@ def auto_populate(mode='all'):
         yield
     finally:
         settings.AUTO_POPULATE = current_population_mode
+
+
+@contextmanager
+def fallbacks(enable=True):
+    """
+    Temporarily switch all language fallbacks on or off.
+
+    Example:
+
+        with fallbacks(False):
+            lang_has_slug = bool(self.slug)
+
+    May be used to enable fallbacks just when they're needed saving on some
+    processing or check if there is a value for the current language (not
+    knowing the language)
+    """
+    current_enable_fallbacks = settings.ENABLE_FALLBACKS
+    settings.ENABLE_FALLBACKS = enable
+    try:
+        yield
+    finally:
+        settings.ENABLE_FALLBACKS = current_enable_fallbacks