notifications: Fix soft-deactivated users don't get push notifications.

Fixes part of zulip#10397.

It was discovered that soft-deactivated users don't get mobile push
notifications for messages on private streams that they have configured
to send push notifications.

Reason: `handle_push_notification` calls `access_message`, and that
logic assumes that a user who is a recipient of a message has an
associated UserMessage row. Those UserMessage rows are created
lazily for soft-deactivated users, so they might not exist (yet)
until the user comes back.

Solution: Removing stream_push_user_ids and stream_email_user_ids
from long_term_idle_user_ids ensures that a UserMessage row is
created in `create_user_messages`.

zerver/lib/actions.py

@@ -1058,9 +1058,21 @@ def is_service_bot(row: Dict[str, Any]) -> bool:
         lambda r: not is_service_bot(r)
     )
 
+    # Issue `#10397`: It was discovered that soft-deactivated users
+    # don't get mobile push notifications for messages on private
+    # streams that they have configured to send push notifications.
+    # Reason: `handle_push_notification` calls `access_message`, and
+    # that logic assumes that a user who is a recipient of a message
+    # has an associated UserMessage row. Those UserMessage rows are
+    # created lazily for soft-deactivated users, so they might not
+    # exist (yet) until the user comes back.
+    # Solution: Removing stream_push_user_ids and stream_email_user_ids
+    # from long_term_idle_user_ids ensures that a UserMessage row is
+    # created in `create_user_messages`.
     long_term_idle_user_ids = get_ids_for(
         lambda r: r['long_term_idle']
-    )
+    ) - stream_push_user_ids \
+      - stream_email_user_ids
 
     # These two bot data structures need to filter from the full set
     # of users who either are receiving the message or might have been

zerver/tests/test_users.py

@@ -40,6 +40,7 @@
 from zerver.lib.stream_topic import StreamTopicTarget
 from zerver.lib.users import user_ids_to_users, access_user_by_id, \
     get_accounts_for_email
+from zerver.lib.soft_deactivation import do_soft_deactivate_user
 
 from django.conf import settings
 
@@ -599,8 +600,9 @@ def test_clear_scheduled_jobs(self) -> None:
 class RecipientInfoTest(ZulipTestCase):
     def test_stream_recipient_info(self) -> None:
         hamlet = self.example_user('hamlet')
-        cordelia = self.example_user('cordelia')
         othello = self.example_user('othello')
+        cordelia = self.example_user('cordelia')
+        do_soft_deactivate_user(cordelia)
 
         realm = hamlet.realm
 
@@ -636,7 +638,7 @@ def test_stream_recipient_info(self) -> None:
             stream_push_user_ids={hamlet.id},
             stream_email_user_ids=set(),
             um_eligible_user_ids=all_user_ids,
-            long_term_idle_user_ids=set(),
+            long_term_idle_user_ids={cordelia.id},
             default_bot_user_ids=set(),
             service_bot_tuples=[],
         )
@@ -659,6 +661,21 @@ def test_stream_recipient_info(self) -> None:
 
         self.assertEqual(info['stream_push_user_ids'], set())
 
+        # Adding Cordelia to stream_push_user_ids removes her from
+        # long_term_idle_user_ids.
+        sub = get_subscription(stream_name, cordelia)
+        sub.push_notifications = True
+        sub.save()
+
+        info = get_recipient_info(
+            recipient=recipient,
+            sender_id=hamlet.id,
+            stream_topic=stream_topic,
+        )
+
+        self.assertEqual(info['stream_push_user_ids'], {cordelia.id})
+        self.assertEqual(info['long_term_idle_user_ids'], set())
+
         # Add a service bot.
         service_bot = do_create_user(
             email='service-bot@zulip.com',