MSC4319: Room member events for invite and knock rooms in the /sync response

proposals/4319-non-stripped-member-in-stripped-state.md

@@ -0,0 +1,69 @@
+# MSC4139: Non-stripped room member event in stripped state
+
+In the Client-Server API, the response of the [`GET /sync`](https://spec.matrix.org/v1.15/client-server-api/#get_matrixclientv3sync)
+endpoint, the `events` array in the `invite_state` for rooms under `invite` and in the `knock_state`
+for rooms under `knock` are defined as containing the stripped state of the room.
+
+This stripped state comes over federation, via the
+[`PUT /invite`](https://spec.matrix.org/v1.15/server-server-api/#put_matrixfederationv2inviteroomideventid)
+and [`PUT /send_knock`](https://spec.matrix.org/v1.15/server-server-api/#put_matrixfederationv1send_knockroomideventid)
+endpoints in the Server-Server API.
+
+In the definition of the [stripped state](https://spec.matrix.org/v1.15/client-server-api/#stripped-state)
+it is recommended to contain the following state events:
+
+- `m.room.create`
+- `m.room.name`
+- `m.room.avatar`
+- `m.room.topic`
+- `m.room.join_rules`
+- `m.room.canonical_alias`
+- `m.room.encryption`
+
+Although these events are useful to be able to present information about the room, they don't
+contain information about the event itself, like the sender of the invite, or when it occurred.
+
+_Note that this specifies behavior that has been implemented for a long time in homeserver
+implementations and that clients already rely on._
+
+## Proposal
+
+The `m.room.member` event that was created during the invite or knock process MUST be present in
+the `events` of the `invite_state` or `knock_state`. Since servers have access to the whole event,
+and for clients to be able to access the time of the event via the `origin_server_ts` field, it
+MUST use the same format as can be found in the `events` of `timeline` and `state` for rooms under
+`join`. This is the format currently defined as
+[`ClientEventWithoutRoomID`](https://spec.matrix.org/v1.15/client-server-api/#get_matrixclientv3sync_response-200_clienteventwithoutroomid).
+
+_Note that the example for the response of `GET /sync` already include the stripped `m.room.member`
+event although it is not specified._
+
+Furthermore, clients need to be able to display information about the sender of an invite, like
+their display name or avatar. The list of events that should be included in the stripped state is
+extended with the stripped `m.room.member` event of the `sender` of the invite.
+
+## Potential issues
+
+By showing more information about the sender of an invite, users might be subject to undesirable
+content like abusive language or images. Mitigating this is out of scope of this MSC, and other MSCs
+exist for this, like [MSC4278](https://github.com/matrix-org/matrix-spec-proposals/pull/4278).
+
+
+## Alternatives
+
+No relevant alternatives.
+
+
+## Security considerations
+
+No potential security issues are known to the author.
+
+
+## Unstable prefix
+
+None necessary, this is adding existing event types into existing arrays.
+
+
+## Dependencies
+
+None.