Fully URL-encode the URL for webmentions

models.py

@@ -1,6 +1,7 @@
 """Datastore model classes."""
 import logging
-import urllib.parse
+import urllib.parse as urlparse
+from urllib.parse import urlencode
 
 from Crypto.PublicKey import RSA
 from django_salmon import magicsigs
@@ -108,10 +109,20 @@ def proxy_url(self):
         """Returns the Bridgy Fed proxy URL to render this response as HTML."""
         if self.source_mf2 or self.source_as2 or self.source_atom:
             source, target = self.key.id().split(' ')
-            return f'{request.host_url}render?' + urllib.parse.urlencode({
-                'source': source,
-                'target': target,
-            })
+            # via https://stackoverflow.com/questions/2506379/add-params-to-given-url-in-python
+            url = f'{request.host_url}render'
+            params = {
+                    'source': source,
+                    'target': target,
+                    }
+
+            url_parts = list(urlparse.urlparse(url))
+            query = dict(urlparse.parse_qsl(url_parts[4]))
+            query.update(params)
+
+            url_parts[4] = urlencode(query)
+
+            return urlparse.urlunparse(url_parts)
 
     @classmethod
     def _id(cls, source, target):

tests/test_models.py

@@ -58,5 +58,5 @@ def test_proxy_url(self):
             self.assertIsNone(resp.proxy_url())
 
             resp.source_as2 = 'as2'
-            self.assertEqual('http://localhost/render?source=abc&target=xyz',
+            self.assertEqual('http://localhost/render?source=abc%26target=xyz',
                              resp.proxy_url())