Support custom python object serialization

chevron/renderer.py

@@ -130,7 +130,7 @@ def _get_partial(name, partials_dict, partials_path, partials_ext):
 
 def render(template='', data={}, partials_path='.', partials_ext='mustache',
            partials_dict={}, padding='', def_ldel='{{', def_rdel='}}',
-           scopes=None, warn=False, keep=False):
+           scopes=None, warn=False, keep=False, serializer=str):
     """Render a mustache template.
 
     Renders a mustache template with a data scope and partial capability.
@@ -179,6 +179,8 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
 
     keep          -- Keep unreplaced tags when a template substitution isn't found in the data
 
+    serializer    -- Python data serializer (str by default)
+
 
     Returns:
 
@@ -237,15 +239,15 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
                 # then get the un-coerced object (next in the stack)
                 thing = scopes[1]
             if not isinstance(thing, unicode_type):
-                thing = unicode(str(thing), 'utf-8')
+                thing = unicode(serializer(thing), 'utf-8')
             output += _html_escape(thing)
 
         # If we're a no html escape tag
         elif tag == 'no escape':
             # Just lookup the key and add it
             thing = _get_key(key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel)
             if not isinstance(thing, unicode_type):
-                thing = unicode(str(thing), 'utf-8')
+                thing = unicode(serializer(thing), 'utf-8')
             output += thing
 
         # If we're a section tag

test_spec.py

@@ -552,6 +552,21 @@ def test_keep_from_partials(self):
         expected = '1st {{ missing_key }} 3rd'
         self.assertEqual(result, expected)
 
+    def test_custom_serializer(self):
+        args = {
+            'template': '{{ value }}',
+            'data': {
+                'value': {
+                    'key': None,
+                },
+            },
+            'serializer': json.dumps,
+        }
+
+        result = chevron.render(**args)
+        expected = '{"key": null}'
+        self.assertEqual(result, expected)
+
 
 # Run unit tests from command line
 if __name__ == "__main__":