Set current language

tests/native/core/test_cache.py

@@ -37,3 +37,12 @@ def test_returns_entry_if_exists(self):
         assert cache.get('chair', 'el') == u'Μια καρέκλα'
         assert cache.get('invalid', 'en') is None
         assert cache.get('invalid', 'el') is None
+
+    def test_contains(self):
+        cache = MemoryCache()
+        cache.update({
+            'lang1': (True, {'source1': {'string': "translation1"},
+                             'source2': {'string': "translation2"}}),
+        })
+        assert 'lang1' in cache
+        assert 'lang2' not in cache

tests/native/core/test_core.py

@@ -212,3 +212,13 @@ def test_plural(self, cache_mock):
                                    u"fr_FR",
                                    params={'cnt': 2})
         assert translation == u'OTHER'
+
+    @patch('transifex.native.core.CDSHandler.fetch_translations')
+    def test_set_current_language(self, mock_cds):
+        mock_cds.return_value = {'el': (True, {})}
+        tx = self._get_tx()
+        tx.remote_languages = [{'code': "el"}]
+        tx.set_current_language('el')
+
+        assert tx.current_language_code == 'el'
+        mock_cds.assert_called_once_with('el')

transifex/native/cache.py

@@ -51,6 +51,12 @@ def update(self, data):
         """
         pass
 
+    def __contains__(self, language_code):
+        """ Check whether language_code has already been added to the cache.
+        """
+
+        pass
+
 
 class MemoryCache(AbstractCache):
     """A cache that stores translations in memory."""
@@ -81,3 +87,6 @@ def get(self, key, language_code):
         except (ValueError, AttributeError):
             pass
         return retrieved_translation
+
+    def __contains__(self, language_code):
+        return language_code in self._translations_by_lang

transifex/native/core.py

@@ -49,8 +49,6 @@ def setup(self,
         """
         if source_language is not None:
             self.source_language_code = source_language
-        if current_language is not None:
-            self.current_language_code = current_language
         if languages is not None:
             self.hardcoded_language_codes = languages
         if missing_policy is not None:
@@ -62,6 +60,9 @@ def setup(self,
                                 secret=secret,
                                 host=cds_host)
 
+        if current_language is not None:
+            self.set_current_language(current_language)
+
     def fetch_languages(self, force=False):
         if self.remote_languages is None or force:
             self.remote_languages = self._cds_handler.fetch_languages()
@@ -73,17 +74,34 @@ def fetch_languages(self, force=False):
         else:
             return self.remote_languages
 
+    def set_current_language(self, language_code, force=False):
+        if language_code not in (language['code']
+                                 for language in self.fetch_languages()):
+            raise ValueError("Language {} is not supported by the application".
+                             format(language_code))
+        if language_code not in self._cache or force:
+            self.fetch_translations(language_code=language_code, force=True)
+        self.current_language_code = language_code
+
     def fetch_translations(self, language_code=None, force=False):
         """Fetch fresh content from the CDS."""
         if language_code is None:
             for language in self.fetch_languages():
                 self.fetch_translations(language['code'], force=force)
         else:
-            translations = self._cds_handler.fetch_translations(language_code)
-            self._cache.update(translations)
+            if language_code not in [language['code']
+                                     for language in self.fetch_languages()]:
+                raise ValueError(
+                    "Language {} is not supported by the application".
+                    format(language_code)
+                )
+            if language_code not in self._cache or force:
+                translations = self._cds_handler.\
+                    fetch_translations(language_code)
+                self._cache.update(translations)
 
     def translate(
-        self, source_string, language_code, is_source=False,
+        self, source_string, language_code=None, is_source=False,
         _context=None, escape=True, params=None
     ):
         """Translate the given string to the provided language.
@@ -106,6 +124,9 @@ def translate(
         if params is None:
             params = {}
 
+        if language_code is None:
+            language_code = self.current_language_code
+
         translation_template = self.get_translation(source_string,
                                                     language_code,
                                                     _context,