[IMP] translate: export empty translations for empty ones

Instead of use the original string by default.

Currently odoo export a PO translation file using the logic:
"If there is not a translation then use the source."

This generate a false 100% of file translated for tools based on PO
files.

This commit change this logic to:
"If there is not a translation then use empty string."

Odoo import a PO translation file supporting empty string because
if a item is empty string odoo use the original source.

Closes #17925

odoo/addons/base/ir/ir_translation.py

@@ -55,9 +55,6 @@ class IrTranslationImport(object):
 
     def push(self, trans_dict):
         """ Feed a translation, as a dictionary, into the cursor """
-        if not trans_dict['value']:
-            return
-
         params = dict(trans_dict, state="translated")
 
         if params['type'] == 'view':

odoo/tests/addons/test_translation_import/tests/test_term_count.py

@@ -1,8 +1,16 @@
 # -*- coding: utf-8 -*-
 
+from contextlib import closing
+
 import odoo
 from odoo.tests import common
 
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO
+
+
 class TestTermCount(common.TransactionCase):
 
     def test_count_term(self):
@@ -30,3 +38,30 @@ class TestTermCount(common.TransactionCase):
         menu.refresh()
         self.assertEqual(menu.name, "New Name")
         self.assertEqual(menu.with_context(lang='fr_FR').name, "Nouveau nom")
+
+    def test_export_empty_string(self):
+        """When the string and the translation is equal the translation is empty"""
+        # Export the translations
+        def update_translations():
+            with closing(StringIO()) as bufferobj:
+                odoo.tools.trans_export('fr_FR', ['test_translation_import'], bufferobj, 'po', self.cr)
+                bufferobj.name = 'test_translation_import/i18n/fr.po'
+                odoo.tools.trans_load_data(self.cr, bufferobj, 'po', 'fr_FR', verbose=False, context={'overwrite': True})
+
+        # Check if the not translated key is empty string
+        update_translations()
+        translation = self.env['ir.translation'].search_count([('src', '=', 'Efgh'), ('value', '=', '')])
+        self.assertTrue(translation, 'The translation of "Efgh" should be empty')
+
+        # Modify the value translated for the equal value of the key
+        menu = self.env.ref('test_translation_import.menu_test_translation_import')
+        menu.name = "New Name"
+        menu.with_context(lang='fr_FR').name = "New Name"
+        update_translations()
+        self.assertEqual(menu.with_context(lang='fr_FR').name, "New Name", 'The translation of "New Name" should be "New Name"')
+
+        # Modify the value translated for another different value
+        menu.name = "New Name"
+        menu.with_context(lang='fr_FR').name = "Nouveau nom"
+        update_translations()
+        self.assertEqual(menu.with_context(lang='fr_FR').name, "Nouveau nom", 'The translation of "New Name" should be "Nouveau nom"')

odoo/tools/translate.py

@@ -683,7 +683,7 @@ def trans_export(lang, modules, buffer, format, cr):
                     # translation template, so no translation value
                     row['translation'] = ''
                 elif not row.get('translation'):
-                    row['translation'] = src
+                    row['translation'] = ''
                 writer.write(row['modules'], row['tnrs'], src, row['translation'], row['comments'])
 
         elif format == 'tgz':