content_translation: stop setting empty translation dict on object for nothing

Getter of content translations were setting an empty translation dict. So
there was ZODB pollution by doing useless changes.

product/ERP5/tests/testContentTranslation.py

@@ -201,6 +201,7 @@ class TestContentTranslation(ERP5TypeTestCase):
     self.assert_(not person.hasJaKanaTranslatedFirstName())
 
     # if there is no translation, original value is returned.
+    self.assertEqual(None, getattr(person, '__translation_dict', None))
     self.assertEqual('Yusei', person.getTranslatedFirstName())
     self.assertEqual('Yusei Tahara', person.getTranslatedTitle())
     self.assertEqual('Yusei', person.getJaKanaTranslatedFirstName())
@@ -208,9 +209,16 @@ class TestContentTranslation(ERP5TypeTestCase):
     self.assertEqual('', person.getTranslatedFirstName(no_original_value=True))
     self.assertEqual('', person.getTranslatedTitle(no_original_value=True))
     self.assertEqual('', person.getJaKanaTranslatedFirstName(no_original_value=True))
+    # Make sure that until any value is set, we do not create useless __translation_dict
+    self.assertEqual(None, getattr(person, '__translation_dict', None))
 
     person.setJaKanaTranslatedFirstName('タハラ')
     person.setJaKanaTranslatedLastName('ユウセイ')
+    # Since we add some translated value, we now must have some data in __translation_dict
+    translation_dict = getattr(person, '__translation_dict', None)
+    self.assertNotEqual(None, translation_dict)
+    self.assertEqual(set([('last_name', 'ja-kana'), ('first_name', 'ja-kana')]),
+                     set(translation_dict.keys()))
 
     self.assert_(person.hasJaKanaTranslatedFirstName())
 

product/ERP5Type/mixin/property_translatable.py

@@ -41,11 +41,17 @@ class PropertyTranslatableBuiltInDictMixIn:
 
   security = ClassSecurityInfo()
 
-  def _getTranslationDict(self):
+  def _getTranslationDict(self, create_if_missing=False):
+    """
+    create_if_missing: force creation of translation dict. It is false by
+                       default to havoid zodb pollution when only try to get
+                       translations
+    """
     try:
       return getattr(self, INTERNAL_TRANSLATION_DICT_NAME)
     except AttributeError:
       dict_ = {}
+      if create_if_missing:
         setattr(self, INTERNAL_TRANSLATION_DICT_NAME, dict_)
         self._p_changed = True
       return dict_
@@ -58,7 +64,8 @@ class PropertyTranslatableBuiltInDictMixIn:
   security.declareProtected(Permissions.ModifyPortalContent,
                             'setPropertyTranslation')
   def setPropertyTranslation(self, property_id, language, original_text, translation):
-    self._getTranslationDict()[(property_id, language)] = (original_text, translation)
+    self._getTranslationDict(create_if_missing=True)[(property_id, language)] = \
+          (original_text, translation)
     self._p_changed = True
 
   security.declareProtected(Permissions.ModifyPortalContent,