AP users: ignore webmention sending failures

since webmention support is optional for web users: https://fed.brid.gy/docs#error-handling

for #512

protocol.py

@@ -277,7 +277,7 @@ class Protocol:
         follower_obj.status = 'active'
         follower_obj.put()
 
-        # send AP Accept
+        # send Accept
         followee_actor_url = g.user.ap_actor()
         accept = {
             '@context': 'https://www.w3.org/ns/activitystreams',

tests/test_activitypub.py

@@ -768,6 +768,31 @@ class ActivityPubTest(TestCase):
                            labels=['notification', 'activity'],
                            object_ids=[FOLLOW['object']])
 
+    def test_inbox_follow_accept_webmention_fails(self, mock_head, mock_get, mock_post):
+        mock_post.side_effect = [
+            requests_response(),         # AP Accept
+            requests.ConnectionError(),  # webmention
+        ]
+        self._test_inbox_follow_accept(FOLLOW_WRAPPED, ACCEPT,
+                                       mock_head, mock_get, mock_post)
+
+        follow = {
+            **FOLLOW_WITH_ACTOR,
+            'url': 'https://mas.to/users/swentel#followed-https://user.com/',
+        }
+        self.assert_object('https://mas.to/6d1a',
+                           domains=['user.com'],
+                           source_protocol='activitypub',
+                           status='complete',
+                           as2=follow,
+                           delivered=[],
+                           type='follow',
+                           labels=['notification', 'activity'],
+                           object_ids=[FOLLOW['object']])
+
+        follower = Follower.query().get()
+        self.assertEqual(follow, follower.last_follow)
+
     def _test_inbox_follow_accept(self, follow_as2, accept_as2,
                                   mock_head, mock_get, mock_post):
         mock_head.return_value = requests_response(url='https://user.com/')
@@ -776,7 +801,8 @@ class ActivityPubTest(TestCase):
             self.as2_resp(ACTOR),
             WEBMENTION_DISCOVERY,
         ]
-        mock_post.return_value = requests_response()
+        if not mock_post.return_value and not mock_post.side_effect:
+            mock_post.return_value = requests_response()
 
         got = self.post('/user.com/inbox', json=follow_as2)
         self.assertEqual(200, got.status_code)

tests/test_web.py

@@ -14,6 +14,7 @@ from oauth_dropins.webutil.appengine_info import APP_ID
 from oauth_dropins.webutil.testutil import requests_response
 from oauth_dropins.webutil.util import json_dumps, json_loads
 import requests
+from requests import HTTPError
 from werkzeug.exceptions import BadGateway, BadRequest
 
 # import first so that Fake is defined before URL routes are registered
@@ -1699,6 +1700,26 @@ class WebProtocolTest(testutil.TestCase):
         self.assert_req(mock_get, 'https://user.com/post')
         mock_post.assert_not_called()
 
+    def test_send_errors(self, mock_get, mock_post):
+        for err in [
+                requests.HTTPError(response=util.Struct(status_code='429', text='')),
+                requests.ConnectionError(),
+        ]:
+            mock_get.return_value = WEBMENTION_REL_LINK
+            mock_post.side_effect = err
+
+            obj = Object(id='http://mas.to/like#ok', as2=test_activitypub.LIKE,
+                         source_protocol='ui')
+            self.assertFalse(Web.send(obj, 'https://user.com/post'))
+
+            self.assert_req(mock_get, 'https://user.com/post')
+            args, kwargs = mock_post.call_args
+            self.assertEqual(('https://user.com/webmention',), args)
+            self.assertEqual({
+                'source': 'http://localhost/convert/ui/web/http:/mas.to/like^^ok',
+                'target': 'https://user.com/post',
+            }, kwargs['data'])
+
     def test_serve(self, _, __):
         obj = Object(id='http://orig', mf2=ACTOR_MF2)
         html, headers = Web.serve(obj)

web.py

@@ -155,14 +155,23 @@ class Web(User, Protocol):
         """Sends a webmention to a given target URL.
 
         See :meth:`Protocol.send` for details.
+
+        *Does not* propagate HTTP errors, DNS or connection failures, or other
+        exceptions, since webmention support is optional for web recipients.
+        https://fed.brid.gy/docs#error-handling
         """
         source_url = obj.proxy_url()
         logger.info(f'Sending webmention from {source_url} to {url}')
 
         endpoint = common.webmention_discover(url).endpoint
-        if endpoint:
-            webmention.send(endpoint, source_url, url)
-            return True
+        try:
+            if endpoint:
+                webmention.send(endpoint, source_url, url)
+                return True
+        except RequestException as e:
+            # log exception, then ignore it
+            util.interpret_http_exception(e)
+            return False
 
     @classmethod
     def fetch(cls, obj, gateway=False, check_backlink=None):