Fixed #19088 -- Always escape % inside blocktrans tag

Thanks vlinhart for the report and Łukasz Rekucki for the patch.

django/templatetags/i18n.py

@@ -110,13 +110,13 @@ class BlockTranslateNode(Node):
         vars = []
         for token in tokens:
             if token.token_type == TOKEN_TEXT:
-                result.append(token.contents)
+                result.append(token.contents.replace('%', '%%'))
             elif token.token_type == TOKEN_VAR:
                 result.append('%%(%s)s' % token.contents)
                 vars.append(token.contents)
         return ''.join(result), vars
 
-    def render(self, context):
+    def render(self, context, nested=False):
         if self.message_context:
             message_context = self.message_context.resolve(context)
         else:
@@ -128,13 +128,10 @@ class BlockTranslateNode(Node):
         # the end of function
         context.update(tmp_context)
         singular, vars = self.render_token_list(self.singular)
-        # Escape all isolated '%'
-        singular = re.sub('%(?!\()', '%%', singular)
         if self.plural and self.countervar and self.counter:
             count = self.counter.resolve(context)
             context[self.countervar] = count
             plural, plural_vars = self.render_token_list(self.plural)
-            plural = re.sub('%(?!\()', '%%', plural)
             if message_context:
                 result = translation.npgettext(message_context, singular,
                                                plural, count)
@@ -151,8 +148,12 @@ class BlockTranslateNode(Node):
         try:
             result = result % data
         except (KeyError, ValueError):
+            if nested:
+                # Either string is malformed, or it's a bug
+                raise TemplateSyntaxError("'blocktrans' is unable to format "
+                    "string returned by gettext: %r using %r" % (result, data))
             with translation.override(None):
-                result = self.render(context)
+                result = self.render(context, nested=True)
         return result
 
 

tests/regressiontests/i18n/tests.py

@@ -269,7 +269,6 @@ class TranslationTests(TestCase):
         (%(person)s is translated as %(personne)s in fr.po)
         Refs #16516.
         """
-        from django.template import Template, Context
         with translation.override('fr'):
             t = Template('{% load i18n %}{% blocktrans %}My name is {{ person }}.{% endblocktrans %}')
             rendered = t.render(Context({'person': 'James'}))
@@ -282,7 +281,6 @@ class TranslationTests(TestCase):
         (%(person) misses a 's' in fr.po, causing the string formatting to fail)
         Refs #18393.
         """
-        from django.template import Template, Context
         with translation.override('fr'):
             t = Template('{% load i18n %}{% blocktrans %}My other name is {{ person }}.{% endblocktrans %}')
             rendered = t.render(Context({'person': 'James'}))
@@ -821,6 +819,20 @@ class MiscTests(TestCase):
             self.assertEqual(t_plur.render(Context({'percent': 42, 'num': 1})), '42% stellt 1 Objekt dar')
             self.assertEqual(t_plur.render(Context({'percent': 42, 'num': 4})), '42% stellt 4 Objekte dar')
 
+    @override_settings(LOCALE_PATHS=extended_locale_paths)
+    def test_percent_formatting_in_blocktrans(self):
+        """
+        Test that using Python's %-formatting is properly escaped in blocktrans,
+        singular or plural
+        """
+        t_sing = Template("{% load i18n %}{% blocktrans %}There are %(num_comments)s comments{% endblocktrans %}")
+        t_plur = Template("{% load i18n %}{% blocktrans count num as number %}%(percent)s% represents {{ num }} object{% plural %}%(percent)s% represents {{ num }} objects{% endblocktrans %}")
+        with translation.override('de'):
+            # Strings won't get translated as they don't match after escaping %
+            self.assertEqual(t_sing.render(Context({'num_comments': 42})), 'There are %(num_comments)s comments')
+            self.assertEqual(t_plur.render(Context({'percent': 42, 'num': 1})), '%(percent)s% represents 1 object')
+            self.assertEqual(t_plur.render(Context({'percent': 42, 'num': 4})), '%(percent)s% represents 4 objects')
+
 
 class ResolutionOrderI18NTests(TestCase):