mentions: Fix subject line and sender for missed-message mentions.

This fixes 2 issues:
* The term "@-mentioned" is simplified to "mentioned".
* We would incorrectly list other people who sent context messages as
  among the people who mentioned you.

zerver/lib/notifications.py

@@ -274,14 +274,7 @@ def do_send_missedmessage_events_reply_in_zulip(user_profile, missed_messages, m
     from zerver.lib.email_mirror import create_missed_message_address
     address = create_missed_message_address(user_profile, missed_messages[0])
 
-    # TODO: For the mention case, senders should just be the people
+    senders = list(set(m.sender for m in missed_messages))
-    # who mentioned you, not the other senders.
-    senders = set(m.sender.full_name for m in missed_messages)
-    sender_str = ", ".join(senders)
-    context.update({
-        'sender_str': sender_str,
-        'realm_str': user_profile.realm.name,
-    })
     if (missed_messages[0].recipient.type == Recipient.HUDDLE):
         display_recipient = get_display_recipient(missed_messages[0].recipient)
         # Make sure that this is a list of strings, not a string.
@@ -301,7 +294,20 @@ def do_send_missedmessage_events_reply_in_zulip(user_profile, missed_messages, m
     elif (missed_messages[0].recipient.type == Recipient.PERSONAL):
         context.update({'private_message': True})
     else:
+        # Keep only the senders who actually mentioned the user
+        #
+        # TODO: When we add wildcard mentions that send emails, add
+        # them to the filter here.
+        senders = list(set(m.sender for m in missed_messages if
+                           UserMessage.objects.filter(message=m, user_profile=user_profile,
+                                                      flags=UserMessage.flags.mentioned).exists()))
         context.update({'at_mention': True})
+
+    context.update({
+        'sender_str': ", ".join(sender.full_name for sender in senders),
+        'realm_str': user_profile.realm.name,
+    })
+
     from_email = None
 
     if len(senders) == 1 and settings.SEND_MISSED_MESSAGE_EMAILS_AS_USER:
@@ -310,8 +316,8 @@ def do_send_missedmessage_events_reply_in_zulip(user_profile, missed_messages, m
         # However, one must ensure the Zulip server is in the SPF
         # record for the domain, or there will be spam/deliverability
         # problems.
-        sender = missed_messages[0].sender
+        sender = senders[0]
-        from_email = '"%s" <%s>' % (sender_str, sender.email)
+        from_email = '"%s" <%s>' % (sender.full_name, sender.email)
         context.update({
             'reply_warning': False,
             'reply_to_zulip': False,

zerver/tests/test_notifications.py

@@ -55,7 +55,7 @@ class TestMissedMessages(ZulipTestCase):
         self.assertIn(body, self.normalize_string(msg.body))
 
     @patch('zerver.lib.email_mirror.generate_random_token')
-    def _extra_context_in_missed_stream_messages(self, send_as_user, mock_random_token):
+    def _extra_context_in_missed_stream_messages_mention(self, send_as_user, mock_random_token):
         # type: (bool, MagicMock) -> None
         tokens = self._get_tokens()
         mock_random_token.side_effect = tokens
@@ -68,6 +68,19 @@ class TestMissedMessages(ZulipTestCase):
         subject = 'Othello, the Moor of Venice mentioned you in Zulip Dev'
         self._test_cases(tokens, msg_id, body, subject, send_as_user)
 
+    @patch('zerver.lib.email_mirror.generate_random_token')
+    def _extra_context_in_missed_stream_messages_mention_two_senders(self, send_as_user, mock_random_token):
+        # type: (bool, MagicMock) -> None
+        tokens = self._get_tokens()
+        mock_random_token.side_effect = tokens
+
+        for i in range(0, 3):
+            self.send_message("cordelia@zulip.com", "Denmark", Recipient.STREAM, str(i))
+        msg_id = self.send_message("othello@zulip.com", "Denmark", Recipient.STREAM, '@**hamlet**')
+        body = 'Denmark > test Cordelia Lear 0 1 2 Othello, the Moor of Venice @**hamlet**'
+        subject = 'Othello, the Moor of Venice mentioned you in Zulip Dev'
+        self._test_cases(tokens, msg_id, body, subject, send_as_user)
+
     @patch('zerver.lib.email_mirror.generate_random_token')
     def _extra_context_in_personal_missed_stream_messages(self, send_as_user, mock_random_token):
         # type: (bool, MagicMock) -> None
@@ -212,11 +225,20 @@ class TestMissedMessages(ZulipTestCase):
     @override_settings(SEND_MISSED_MESSAGE_EMAILS_AS_USER=True)
     def test_extra_context_in_missed_stream_messages_as_user(self):
         # type: () -> None
-        self._extra_context_in_missed_stream_messages(True)
+        self._extra_context_in_missed_stream_messages_mention(True)
 
     def test_extra_context_in_missed_stream_messages(self):
         # type: () -> None
-        self._extra_context_in_missed_stream_messages(False)
+        self._extra_context_in_missed_stream_messages_mention(False)
+
+    @override_settings(SEND_MISSED_MESSAGE_EMAILS_AS_USER=True)
+    def test_extra_context_in_missed_stream_messages_as_user_two_senders(self):
+        # type: () -> None
+        self._extra_context_in_missed_stream_messages_mention_two_senders(True)
+
+    def test_extra_context_in_missed_stream_messages_two_senders(self):
+        # type: () -> None
+        self._extra_context_in_missed_stream_messages_mention_two_senders(False)
 
     def test_reply_to_email_in_personal_missed_stream_messages(self):
         # type: () -> None