Modify /state/{eventType}/{stateKey} to return the event at the time the user left

Or live, depending on their current state. Hopefully fixes some sytests!

clientapi/routing/routing.go

@@ -216,7 +216,7 @@ func Setup(
 			eventType = eventType[:len(eventType)-1]
 		}
 		eventFormat := req.URL.Query().Get("format") == "event"
-		return OnIncomingStateTypeRequest(req.Context(), rsAPI, vars["roomID"], eventType, "", eventFormat)
+		return OnIncomingStateTypeRequest(req.Context(), device, rsAPI, vars["roomID"], eventType, "", eventFormat)
 	})).Methods(http.MethodGet, http.MethodOptions)
 
 	r0mux.Handle("/rooms/{roomID}/state/{type}/{stateKey}", httputil.MakeAuthAPI("room_state", userAPI, func(req *http.Request, device *userapi.Device) util.JSONResponse {
@@ -225,7 +225,7 @@ func Setup(
 			return util.ErrorResponse(err)
 		}
 		eventFormat := req.URL.Query().Get("format") == "event"
-		return OnIncomingStateTypeRequest(req.Context(), rsAPI, vars["roomID"], vars["type"], vars["stateKey"], eventFormat)
+		return OnIncomingStateTypeRequest(req.Context(), device, rsAPI, vars["roomID"], vars["type"], vars["stateKey"], eventFormat)
 	})).Methods(http.MethodGet, http.MethodOptions)
 
 	r0mux.Handle("/rooms/{roomID}/state/{eventType:[^/]+/?}",

clientapi/routing/state.go

@@ -22,6 +22,7 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/syncapi/types"
+	userapi "github.com/matrix-org/dendrite/userapi/api"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 	log "github.com/sirupsen/logrus"
@@ -99,16 +100,40 @@ func OnIncomingStateRequest(ctx context.Context, rsAPI api.RoomserverInternalAPI
 // state to see if there is an event with that type and state key, if there
 // is then (by default) we return the content, otherwise a 404.
 // If eventFormat=true, sends the whole event else just the content.
-func OnIncomingStateTypeRequest(ctx context.Context, rsAPI api.RoomserverInternalAPI, roomID, evType, stateKey string, eventFormat bool) util.JSONResponse {
+func OnIncomingStateTypeRequest(
+	ctx context.Context, device *userapi.Device, rsAPI api.RoomserverInternalAPI,
+	roomID, evType, stateKey string, eventFormat bool,
+) util.JSONResponse {
 	// TODO(#287): Auth request and handle the case where the user has left (where
 	// we should return the state at the poin they left)
+
+	var membershipRes api.QueryMembershipForUserResponse
+	err := rsAPI.QueryMembershipForUser(ctx, &api.QueryMembershipForUserRequest{
+		RoomID: roomID,
+		UserID: device.UserID,
+	}, &membershipRes)
+	if err != nil {
+		util.GetLogger(ctx).WithError(err).Error("Failed to QueryMembershipForUser")
+		return jsonerror.InternalServerError()
+	}
+	if !membershipRes.HasBeenInRoom {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("Unknown room or user is not in room"),
+		}
+	}
+
 	util.GetLogger(ctx).WithFields(log.Fields{
 		"roomID":         roomID,
 		"evType":         evType,
 		"stateKey":       stateKey,
+		"state_at_event": !membershipRes.IsInRoom,
 	}).Info("Fetching state")
 
-	stateReq := api.QueryLatestEventsAndStateRequest{
+	var event *gomatrixserverlib.HeaderedEvent
+	if membershipRes.IsInRoom {
+		stateRes := api.QueryLatestEventsAndStateResponse{}
+		if err := rsAPI.QueryLatestEventsAndState(ctx, &api.QueryLatestEventsAndStateRequest{
 			RoomID: roomID,
 			StateToFetch: []gomatrixserverlib.StateKeyTuple{
 				gomatrixserverlib.StateKeyTuple{
@@ -116,15 +141,36 @@ func OnIncomingStateTypeRequest(ctx context.Context, rsAPI api.RoomserverInterna
 					StateKey:  stateKey,
 				},
 			},
-	}
+		}, &stateRes); err != nil {
-	stateRes := api.QueryLatestEventsAndStateResponse{}
-
-	if err := rsAPI.QueryLatestEventsAndState(ctx, &stateReq, &stateRes); err != nil {
 			util.GetLogger(ctx).WithError(err).Error("queryAPI.QueryLatestEventsAndState failed")
 			return jsonerror.InternalServerError()
 		}
+		if len(stateRes.StateEvents) > 0 {
+			event = &stateRes.StateEvents[0]
+		}
+	} else {
+		// fetch the state at the time they left
+		var stateAfterRes api.QueryStateAfterEventsResponse
+		err = rsAPI.QueryStateAfterEvents(ctx, &api.QueryStateAfterEventsRequest{
+			RoomID:       roomID,
+			PrevEventIDs: []string{membershipRes.EventID},
+			StateToFetch: []gomatrixserverlib.StateKeyTuple{
+				{
+					EventType: evType,
+					StateKey:  stateKey,
+				},
+			},
+		}, &stateAfterRes)
+		if err != nil {
+			util.GetLogger(ctx).WithError(err).Error("Failed to QueryMembershipForUser")
+			return jsonerror.InternalServerError()
+		}
+		if len(stateAfterRes.StateEvents) > 0 {
+			event = &stateAfterRes.StateEvents[0]
+		}
+	}
 
-	if len(stateRes.StateEvents) == 0 {
+	if event == nil {
 		return util.JSONResponse{
 			Code: http.StatusNotFound,
 			JSON: jsonerror.NotFound("cannot find state"),
@@ -132,7 +178,7 @@ func OnIncomingStateTypeRequest(ctx context.Context, rsAPI api.RoomserverInterna
 	}
 
 	stateEvent := stateEventInStateResp{
-		ClientEvent: gomatrixserverlib.HeaderedToClientEvent(stateRes.StateEvents[0], gomatrixserverlib.FormatAll),
+		ClientEvent: gomatrixserverlib.HeaderedToClientEvent(*event, gomatrixserverlib.FormatAll),
 	}
 
 	var res interface{}