events: Fix applying stream creation events in apply_event.

There was a bug in apply_event code where only a stream which
is not private is added to the "never_subscribed" data after
a stream creation event. Instead, it should be added to the
"never_subscribed" data irrespective of permission policy of
the stream as we already send stream creation events only to
those users who can access the stream. Due to the current
bug, private streams were not being added to "never_subscribed"
data in apply_event for admins as well. This commit fixes it
and also makes sure the "never_subscribed" list is sorted
which was not done before and was also a bug.

The bugs mentioned above were unnoticed as the tests did not
cover these cases and this commit also adds tests for those
cases.

zerver/lib/events.py

@@ -997,7 +997,6 @@ def apply_event(
     elif event["type"] == "stream":
         if event["op"] == "create":
             for stream in event["streams"]:
-                if not stream["invite_only"]:
                 stream_data = copy.deepcopy(stream)
                 if include_subscribers:
                     stream_data["subscribers"] = []
@@ -1013,6 +1012,7 @@ def apply_event(
                 if "streams" in state:
                     state["streams"].append(stream)
 
+            state["never_subscribed"].sort(key=lambda elt: elt["name"])
             if "streams" in state:
                 state["streams"].sort(key=lambda elt: elt["name"])
 

zerver/lib/test_classes.py

@@ -1347,12 +1347,16 @@ Output:
         return stream.id
 
     # Subscribe to a stream directly
-    def subscribe(self, user_profile: UserProfile, stream_name: str) -> Stream:
+    def subscribe(
+        self, user_profile: UserProfile, stream_name: str, invite_only: bool = False
+    ) -> Stream:
         realm = user_profile.realm
         try:
             stream = get_stream(stream_name, user_profile.realm)
         except Stream.DoesNotExist:
-            stream, from_stream_creation = create_stream_if_needed(realm, stream_name)
+            stream, from_stream_creation = create_stream_if_needed(
+                realm, stream_name, invite_only=invite_only
+            )
         bulk_add_subscriptions(realm, [stream], [user_profile], acting_user=None)
         return stream
 

zerver/tests/test_events.py

@@ -3044,6 +3044,44 @@ class UserDisplayActionTest(BaseAction):
         check_realm_user_update("events[0]", events[0], "delivery_email")
         self.assertEqual(events[0]["person"]["delivery_email"], cordelia.delivery_email)
 
+    def test_stream_creation_events(self) -> None:
+        action = lambda: self.subscribe(self.example_user("hamlet"), "Test stream")
+        events = self.verify_action(action, num_events=2)
+        check_stream_create("events[0]", events[0])
+        check_subscription_add("events[1]", events[1])
+
+        # Check that guest user does not receive stream creation itself of public
+        # stream.
+        self.user_profile = self.example_user("polonius")
+        action = lambda: self.subscribe(self.example_user("hamlet"), "Test stream 2")
+        events = self.verify_action(action, num_events=0, state_change_expected=False)
+
+        self.user_profile = self.example_user("hamlet")
+        action = lambda: self.subscribe(
+            self.example_user("hamlet"), "Private test stream", invite_only=True
+        )
+        events = self.verify_action(action, num_events=2)
+        check_stream_create("events[0]", events[0])
+        check_subscription_add("events[1]", events[1])
+
+        # A non-admin user who is not subscribed to the private stream does not
+        # receive stream creation event.
+        self.user_profile = self.example_user("othello")
+        action = lambda: self.subscribe(
+            self.example_user("hamlet"), "Private test stream 2", invite_only=True
+        )
+        events = self.verify_action(action, num_events=0, state_change_expected=False)
+
+        # An admin user who is not subscribed to the private stream also
+        # receives stream creation event.
+        action = lambda: self.subscribe(
+            self.example_user("hamlet"), "Private test stream 3", invite_only=True
+        )
+        self.user_profile = self.example_user("iago")
+        events = self.verify_action(action, num_events=2)
+        check_stream_create("events[0]", events[0])
+        check_subscription_peer_add("events[1]", events[1])
+
 
 class SubscribeActionTest(BaseAction):
     def test_subscribe_events(self) -> None: