Add an admin API endpoint to support per-user feature flags (#15344)

2 files changed, 121 insertions, 0 deletions

diff --git a/synapse/rest/admin/__init__.py b/synapse/rest/admin/__init__.py
index 770df261ce..c729364839 100644
--- a/synapse/rest/admin/__init__.py
+++ b/synapse/rest/admin/__init__.py
@@ -39,6 +39,7 @@ from synapse.rest.admin.event_reports import (
     EventReportDetailRestServlet,
     EventReportsRestServlet,
 )
+from synapse.rest.admin.experimental_features import ExperimentalFeaturesRestServlet
 from synapse.rest.admin.federation import (
     DestinationMembershipRestServlet,
     DestinationResetConnectionRestServlet,
@@ -292,6 +293,7 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     BackgroundUpdateEnabledRestServlet(hs).register(http_server)
     BackgroundUpdateRestServlet(hs).register(http_server)
     BackgroundUpdateStartJobRestServlet(hs).register(http_server)
+    ExperimentalFeaturesRestServlet(hs).register(http_server)
 
 
 def register_servlets_for_client_rest_resource(
diff --git a/synapse/rest/admin/experimental_features.py b/synapse/rest/admin/experimental_features.py
new file mode 100644
index 0000000000..1d409ac2b7
--- /dev/null
+++ b/synapse/rest/admin/experimental_features.py
@@ -0,0 +1,119 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+
+from enum import Enum
+from http import HTTPStatus
+from typing import TYPE_CHECKING, Dict, Tuple
+
+from synapse.api.errors import SynapseError
+from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
+from synapse.rest.admin import admin_patterns, assert_requester_is_admin
+from synapse.types import JsonDict, UserID
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+
+class ExperimentalFeature(str, Enum):
+    """
+    Currently supported per-user features
+    """
+
+    MSC3026 = "msc3026"
+    MSC2654 = "msc2654"
+    MSC3881 = "msc3881"
+    MSC3967 = "msc3967"
+
+
+class ExperimentalFeaturesRestServlet(RestServlet):
+    """
+    Enable or disable experimental features for a user or determine which features are enabled
+    for a given user
+    """
+
+    PATTERNS = admin_patterns("/experimental_features/(?P<user_id>[^/]*)")
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastores().main
+        self.is_mine = hs.is_mine
+
+    async def on_GET(
+        self,
+        request: SynapseRequest,
+        user_id: str,
+    ) -> Tuple[int, JsonDict]:
+        """
+        List which features are enabled for a given user
+        """
+        await assert_requester_is_admin(self.auth, request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.is_mine(target_user):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "User must be local to check what experimental features are enabled.",
+            )
+
+        enabled_features = await self.store.list_enabled_features(user_id)
+
+        user_features = {}
+        for feature in ExperimentalFeature:
+            if feature in enabled_features:
+                user_features[feature] = True
+            else:
+                user_features[feature] = False
+        return HTTPStatus.OK, {"features": user_features}
+
+    async def on_PUT(
+        self, request: SynapseRequest, user_id: str
+    ) -> Tuple[HTTPStatus, Dict]:
+        """
+        Enable or disable the provided features for the requester
+        """
+        await assert_requester_is_admin(self.auth, request)
+
+        body = parse_json_object_from_request(request)
+
+        target_user = UserID.from_string(user_id)
+        if not self.is_mine(target_user):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "User must be local to enable experimental features.",
+            )
+
+        features = body.get("features")
+        if not features:
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST, "You must provide features to set."
+            )
+
+        # validate the provided features
+        validated_features = {}
+        for feature, enabled in features.items():
+            try:
+                validated_feature = ExperimentalFeature(feature)
+                validated_features[validated_feature] = enabled
+            except ValueError:
+                raise SynapseError(
+                    HTTPStatus.BAD_REQUEST,
+                    f"{feature!r} is not recognised as a valid experimental feature.",
+                )
+
+        await self.store.set_features_for_user(user_id, validated_features)
+
+        return HTTPStatus.OK, {}