Add MSC2716 to room capabilities

Spawned from https://github.com/matrix-org/matrix-js-sdk/pull/2299#discussion_r852893524

2 files changed, 36 insertions, 1 deletions

diff --git a/synapse/api/room_versions.py b/synapse/api/room_versions.py
index a747a40814..12f00d0a18 100644
--- a/synapse/api/room_versions.py
+++ b/synapse/api/room_versions.py
@@ -313,3 +313,28 @@ MSC3244_CAPABILITIES = {
         ),
     )
 }
+
+MSC2716_CAPABILITIES = {
+    cap.identifier: {
+        "preferred": cap.preferred_version.identifier
+        if cap.preferred_version is not None
+        else None,
+        "support": [
+            v.identifier
+            for v in KNOWN_ROOM_VERSIONS.values()
+            if cap.support_check_lambda(v)
+        ],
+    }
+    for cap in (
+        RoomVersionCapability(
+            "historical",
+            RoomVersions.MSC2716v3,
+            lambda room_version: room_version.msc2716_historical,
+        ),
+        RoomVersionCapability(
+            "redactions",
+            RoomVersions.MSC2716v3,
+            lambda room_version: room_version.msc2716_redactions,
+        ),
+    )
+}
diff --git a/synapse/rest/client/capabilities.py b/synapse/rest/client/capabilities.py
index 4237071c61..526335a172 100644
--- a/synapse/rest/client/capabilities.py
+++ b/synapse/rest/client/capabilities.py
@@ -15,7 +15,11 @@ import logging
 from http import HTTPStatus
 from typing import TYPE_CHECKING, Tuple
 
-from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, MSC3244_CAPABILITIES
+from synapse.api.room_versions import (
+    KNOWN_ROOM_VERSIONS,
+    MSC3244_CAPABILITIES,
+    MSC2716_CAPABILITIES,
+)
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet
 from synapse.http.site import SynapseRequest
@@ -72,6 +76,12 @@ class CapabilitiesRestServlet(RestServlet):
                 "org.matrix.msc3244.room_capabilities"
             ] = MSC3244_CAPABILITIES
 
+        logger.info("ewffewaafewafew")
+        if self.config.experimental.msc2716_enabled:
+            response["capabilities"]["m.room_versions"][
+                "org.matrix.msc2716.room_capabilities"
+            ] = MSC2716_CAPABILITIES
+
         if self.config.experimental.msc3720_enabled:
             response["capabilities"]["org.matrix.msc3720.account_status"] = {
                 "enabled": True,