tornado: Stop collapsing "restart" events via virtual events.

Collapsing was done incorrectly, as 65c400e06d added `zulip_version`
and `zulip_feature_level`, but did not update the virtual event logic
to copy those new values into the virtual event.

However, it is unlikely that a server will be upgraded multiple times
in quick enough succession for this to ever be relevant.  Remove the
logic, which is additional complication for little or no gain.

zerver/tests/test_event_queue.py

@@ -1312,9 +1312,7 @@ class EventQueueTest(ZulipTestCase):
             umfe(timestamp=1, messages=[101]),
             umfe(timestamp=2, messages=[201, 202]),
             dict(type="unknown"),
-            dict(type="restart", server_generation="1"),
             umfe(timestamp=3, messages=[301, 302, 303]),
-            dict(type="restart", server_generation="2"),
             umfe(timestamp=4, messages=[401, 402, 403, 404]),
         ]
 
@@ -1327,9 +1325,8 @@ class EventQueueTest(ZulipTestCase):
             queue.contents(),
             [
                 dict(id=2, type="unknown"),
-                dict(id=5, type="restart", server_generation="2"),
                 dict(
-                    id=6,
+                    id=4,
                     type="update_message_flags",
                     operation="add",
                     flag="read",
@@ -1353,9 +1350,8 @@ class EventQueueTest(ZulipTestCase):
             queue.contents(),
             [
                 dict(id=2, type="unknown"),
-                dict(id=5, type="restart", server_generation="2"),
                 dict(
-                    id=6,
+                    id=4,
                     type="update_message_flags",
                     operation="add",
                     flag="read",
@@ -1364,7 +1360,7 @@ class EventQueueTest(ZulipTestCase):
                     messages=[101, 201, 202, 301, 302, 303, 401, 402, 403, 404],
                 ),
                 dict(
-                    id=7,
+                    id=5,
                     type="update_message_flags",
                     operation="add",
                     flag="read",
@@ -1465,23 +1461,28 @@ class EventQueueTest(ZulipTestCase):
         of the same form.  See the code in
         EventQueue.push for more context.
         """
+
+        event = dict(
+            id=0,
+            type="update_message_flags",
+            operation="add",
+            flag="read",
+            all=False,
+            timestamp=1,
+            messages=[101],
+        )
+
         client = self.get_client_descriptor()
         queue = client.event_queue
-        queue.push({"type": "restart", "server_generation": 1, "timestamp": "1"})
-        # Verify the server_generation event is stored as a virtual event
-        self.assertEqual(
-            queue.virtual_events,
-            {"restart": {"id": 0, "type": "restart", "server_generation": 1, "timestamp": "1"}},
-        )
+        queue.push(event)
+        # Verify the event is stored as a virtual event
+        self.assertEqual(queue.virtual_events, {"flags/add/read": event})
         # And we can reconstruct newest_pruned_id etc.
         self.verify_to_dict_end_to_end(client)
 
         queue.push({"type": "unknown", "timestamp": "1"})
         self.assertEqual(list(queue.queue), [{"id": 1, "type": "unknown", "timestamp": "1"}])
-        self.assertEqual(
-            queue.virtual_events,
-            {"restart": {"id": 0, "type": "restart", "server_generation": 1, "timestamp": "1"}},
-        )
+        self.assertEqual(queue.virtual_events, {"flags/add/read": event})
         # And we can still reconstruct newest_pruned_id etc. correctly
         self.verify_to_dict_end_to_end(client)
 
@@ -1489,7 +1490,7 @@ class EventQueueTest(ZulipTestCase):
         self.assertEqual(
             queue.contents(),
             [
-                {"id": 0, "type": "restart", "server_generation": 1, "timestamp": "1"},
+                event,
                 {"id": 1, "type": "unknown", "timestamp": "1"},
             ],
         )

zerver/tests/test_event_system.py

@@ -1143,13 +1143,8 @@ class RestartEventsTest(ZulipTestCase):
 
         send_restart_events(immediate=True)
 
-        # For now we only verify that a virtual event
-        # gets added to the client's event_queue.  We
-        # may decide to write a deeper test in the future
-        # that exercises the finish_handler.
-        virtual_events = client.event_queue.virtual_events
-        self.assert_length(virtual_events, 1)
-        restart_event = virtual_events["restart"]
+        self.assert_length(client.event_queue.queue, 1)
+        restart_event = client.event_queue.queue[0]
 
         check_restart_event("restart_event", restart_event)
         self.assertEqual(

zerver/tornado/event_queue.py

@@ -359,9 +359,8 @@ class EventQueue:
         event["id"] = self.next_event_id
         self.next_event_id += 1
         full_event_type = compute_full_event_type(event)
-        if full_event_type == "restart" or (
-            full_event_type.startswith("flags/")
-            and not full_event_type.startswith("flags/remove/read")
+        if full_event_type.startswith("flags/") and not full_event_type.startswith(
+            "flags/remove/read"
         ):
             # virtual_events are an optimization that allows certain
             # simple events, such as update_message_flags events that
@@ -384,13 +383,10 @@ class EventQueue:
             # Update the virtual event with the values from the event
             virtual_event = self.virtual_events[full_event_type]
             virtual_event["id"] = event["id"]
+            virtual_event["messages"] += event["messages"]
             if "timestamp" in event:
                 virtual_event["timestamp"] = event["timestamp"]
 
-            if full_event_type == "restart":
-                virtual_event["server_generation"] = event["server_generation"]
-            elif full_event_type.startswith("flags/"):
-                virtual_event["messages"] += event["messages"]
         else:
             self.queue.append(event)