atom.activities_to_atom: handle image attachments without url field

fixes https://console.cloud.google.com/errors/detail/CNXAnpyGjOeL8gE;time=P30D?project=bridgy-federated

README.md

@@ -283,6 +283,8 @@ Changelog
 
 ### 6.3 - unreleased
 
+* `atom`:
+  * `activities_to_atom`: handle image attachments without `url` field.
 * `bluesky`:
   * `to_as1`:
     * Support `app.bsky.feed.defs#notFoundPost` records.

granary/atom.py

@@ -442,12 +442,14 @@ def _prepare_activity(a, reader=True):
     if not image:
       continue
     url = image.get('url') or image.get('id')
+    if not url:
+      continue
     parsed = urllib.parse.urlparse(url)
     rest = urllib.parse.urlunparse(('', '') + parsed[2:])
     img_src_re = re.compile(r"""src *= *['"] *((https?:)?//%s)?%s *['"]""" %
                             (re.escape(parsed.netloc),
                              _encode_ampersands(re.escape(rest))))
-    if (url and url not in image_urls_seen and
+    if (url not in image_urls_seen and
         not img_src_re.search(obj['rendered_content'])):
       children.append(microformats2.img(url))
       image_urls_seen.add(url)

granary/tests/test_atom.py

@@ -413,6 +413,14 @@ def test_render_untitled_image(self):
       atom.activities_to_atom([activity], test_instagram.ACTOR,
                               title='my title'))
 
+  def test_render_image_without_url(self):
+    activity = copy.deepcopy(test_instagram.ACTIVITY)
+    activity['object']['attachments'].append(
+      {'objectType': 'image', 'image': {'href': 'http://image/2'}})
+
+    # just check that we don't crash
+    atom.activities_to_atom([activity], test_instagram.ACTOR)
+
   def test_render_share(self):
     activity = {
       'verb': 'share',