push_notifs: Set APNs topic individually on each notification.

This makes it possible to send notifications to more than one app ID
from the same server: for example, the main Zulip mobile app and the
new Flutter-based app, which has a separate app ID for use through its
beta period so that it can be installed alongside the existing app.

docs/production/mobile-push-notifications.md

@@ -226,9 +226,6 @@ push notifications through the new app is quite straightforward:
     `APNS_TOKEN_KEY_ID` to the corresponding 10-character key ID, and
     `APNS_TEAM_ID` to your 10-character Apple team ID.
 
-- Set the `APNS_TOPIC` setting to the ID for
-  your app (for the official Zulip apps, it's `org.zulip.Zulip`).
-
 - Restart the Zulip server.
 
 [apple-doc-cert]: https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/establishing_a_certificate-based_connection_to_apns

zerver/lib/push_notifications.py

@@ -178,10 +178,14 @@ def get_apns_context() -> Optional[APNsContext]:
             key=settings.APNS_TOKEN_KEY_FILE,
             key_id=settings.APNS_TOKEN_KEY_ID,
             team_id=settings.APNS_TEAM_ID,
-            topic=settings.APNS_TOPIC,
             max_connection_attempts=APNS_MAX_RETRIES,
             use_sandbox=settings.APNS_SANDBOX,
             err_func=err_func,
+            # The actual APNs topic will vary between notifications,
+            # so we set it there, overriding any value we put here.
+            # We can't just leave this out, though, because then
+            # the constructor attempts to guess.
+            topic="invalid.nonsense",
         )
 
     apns = loop.run_until_complete(make_apns())
@@ -262,6 +266,7 @@ def send_apple_push_notification(
     payload_data = dict(modernize_apns_payload(payload_data))
     message = {**payload_data.pop("custom", {}), "aps": payload_data}
 
+    have_missing_app_id = False
     for device in devices:
         if device.ios_app_id is None:
             # This should be present for all APNs tokens, as an invariant maintained
@@ -269,13 +274,19 @@ def send_apple_push_notification(
             logger.error(
                 "APNs: Missing ios_app_id for user %s device %s", user_identity, device.token
             )
+            have_missing_app_id = True
+    if have_missing_app_id:
+        devices = [device for device in devices if device.ios_app_id is not None]
 
     async def send_all_notifications() -> Iterable[
         Tuple[DeviceToken, Union[aioapns.common.NotificationResult, BaseException]]
     ]:
         requests = [
             aioapns.NotificationRequest(
-                device_token=device.token, message=message, time_to_live=24 * 3600
+                apns_topic=device.ios_app_id,
+                device_token=device.token,
+                message=message,
+                time_to_live=24 * 3600,
             )
             for device in devices
         ]

zerver/tests/test_push_notifications.py

@@ -1491,17 +1491,20 @@ class PushNotificationTest(BouncerTestCase):
             apns_context.loop.close()
 
     def setup_apns_tokens(self) -> None:
-        self.tokens = ["aaaa", "bbbb"]
-        for token in self.tokens:
+        self.tokens = [("aaaa", "org.zulip.Zulip"), ("bbbb", "com.zulip.flutter")]
+        for token, appid in self.tokens:
             PushDeviceToken.objects.create(
                 kind=PushDeviceToken.APNS,
                 token=hex_to_b64(token),
                 user=self.user_profile,
-                ios_app_id="org.zulip.Zulip",
+                ios_app_id=appid,
             )
 
-        self.remote_tokens = [("cccc", "ffff")]
-        for id_token, uuid_token in self.remote_tokens:
+        self.remote_tokens = [
+            ("cccc", "dddd", "org.zulip.Zulip"),
+            ("eeee", "ffff", "com.zulip.flutter"),
+        ]
+        for id_token, uuid_token, appid in self.remote_tokens:
             # We want to set up both types of RemotePushDeviceToken here:
             # the legacy one with user_id and the new with user_uuid.
             # This allows tests to work with either, without needing to
@@ -1509,12 +1512,14 @@ class PushNotificationTest(BouncerTestCase):
             RemotePushDeviceToken.objects.create(
                 kind=RemotePushDeviceToken.APNS,
                 token=hex_to_b64(id_token),
+                ios_app_id=appid,
                 user_id=self.user_profile.id,
                 server=RemoteZulipServer.objects.get(uuid=self.server_uuid),
             )
             RemotePushDeviceToken.objects.create(
                 kind=RemotePushDeviceToken.APNS,
                 token=hex_to_b64(uuid_token),
+                ios_app_id=appid,
                 user_uuid=self.user_profile.uuid,
                 server=RemoteZulipServer.objects.get(uuid=self.server_uuid),
             )
@@ -1607,6 +1612,16 @@ class HandlePushNotificationTest(PushNotificationTest):
             }
             send_notification.return_value.is_successful = True
             handle_push_notification(self.user_profile.id, missed_message)
+            self.assertEqual(
+                {
+                    (args[0][0].device_token, args[0][0].apns_topic)
+                    for args in send_notification.call_args_list
+                },
+                {
+                    (device.token, device.ios_app_id)
+                    for device in RemotePushDeviceToken.objects.filter(kind=PushDeviceToken.APNS)
+                },
+            )
             self.assertEqual(
                 views_logger.output,
                 [

zproject/default_settings.py

@@ -405,8 +405,8 @@ APNS_TOKEN_KEY_FILE: Optional[str] = None
 APNS_TOKEN_KEY_ID = get_secret("apns_token_key_id", development_only=True)
 APNS_TEAM_ID = get_secret("apns_team_id", development_only=True)
 APNS_SANDBOX = True
-APNS_TOPIC = "org.zulip.Zulip"
-# ZULIP_IOS_APP_ID is obsolete
+# APNS_TOPIC is obsolete. Clients now pass the APNs topic to use.
+# ZULIP_IOS_APP_ID is obsolete. Clients now pass the iOS app ID to use for APNs.
 
 # Limits related to the size of file uploads; last few in MB.
 DATA_UPLOAD_MAX_MEMORY_SIZE = 25 * 1024 * 1024