Put MSC4308 behind the MSC4306 feature flag

Author: reivilibre

synapse/config/experimental.py

@@ -583,5 +583,5 @@ def read_config(
         self.msc4155_enabled: bool = experimental.get("msc4155_enabled", False)
 
         # MSC4306: Thread Subscriptions
-        # (and MSC4308: sliding sync extension for thread subscriptions)
+        # (and MSC4308: Thread Subscriptions extension to Sliding Sync)
         self.msc4306_enabled: bool = experimental.get("msc4306_enabled", False)

synapse/handlers/sliding_sync/extensions.py

@@ -70,6 +70,7 @@ def __init__(self, hs: "HomeServer"):
         self.event_sources = hs.get_event_sources()
         self.device_handler = hs.get_device_handler()
         self.push_rules_handler = hs.get_push_rules_handler()
+        self._enable_thread_subscriptions = hs.config.experimental.msc4306_enabled
 
     @trace
     async def get_extensions_response(
@@ -163,7 +164,10 @@ async def get_extensions_response(
             )
 
         thread_subs_coro = None
-        if sync_config.extensions.thread_subscriptions is not None:
+        if (
+            sync_config.extensions.thread_subscriptions is not None
+            and self._enable_thread_subscriptions
+        ):
             thread_subs_coro = self.get_thread_subscriptions_extension_response(
                 sync_config=sync_config,
                 thread_subscriptions_request=sync_config.extensions.thread_subscriptions,

tests/rest/client/sliding_sync/test_extension_thread_subscriptions.py

@@ -38,6 +38,11 @@ class SlidingSyncThreadSubscriptionsExtensionTestCase(SlidingSyncBase):
         sync.register_servlets,
     ]
 
+    def default_config(self) -> JsonDict:
+        config = super().default_config()
+        config["experimental_features"] = {"msc4306_enabled": True}
+        return config
+
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.store = hs.get_datastores().main
         self.storage_controllers = hs.get_storage_controllers()