Re-add creation of room by visiting the URL

Creates an unencrypted room if you land on an old-style simple URL
forn a room that doesn't exist.

src/room/useLoadGroupCall.ts

@@ -20,10 +20,12 @@ import { ClientEvent, MatrixClient } from "matrix-js-sdk/src/client";
 import { SyncState } from "matrix-js-sdk/src/sync";
 import { useTranslation } from "react-i18next";
 import { MatrixRTCSession } from "matrix-js-sdk/src/matrixrtc/MatrixRTCSession";
+import { MatrixError } from "matrix-js-sdk";
 
 import type { Room } from "matrix-js-sdk/src/models/room";
 import type { GroupCall } from "matrix-js-sdk/src/webrtc/groupCall";
 import { useEnableE2EE } from "../settings/useSetting";
+import { createRoom, isLocalRoomId, roomNameFromRoomId } from "../matrix-utils";
 
 export type GroupCallLoaded = {
   kind: "loaded";
@@ -69,6 +71,7 @@ export const useLoadGroupCall = (
         // Also, we explicitly look up the room alias here. We previously just tried to
         // join anyway but the js-sdk recreates the room if you pass the alias for a
         // room you're already joined to (which it probably ought not to).
+        try {
           const lookupResult = await client.getRoomIdForAlias(
             roomIdOrAlias.toLowerCase()
           );
@@ -84,6 +87,25 @@ export const useLoadGroupCall = (
               `Already in room ${lookupResult.room_id}, not rejoining.`
             );
           }
+        } catch (e) {
+          if (
+            isLocalRoomId(roomIdOrAlias, client) &&
+            (e as MatrixError).errcode === "M_NOT_FOUND"
+          ) {
+            // legacy path: create an unencrypted room if the user lands on a URL for a room that
+            // doesn't exist
+            const result = await createRoom(
+              client,
+              roomNameFromRoomId(roomIdOrAlias),
+              false
+            );
+
+            await client.waitUntilRoomReadyForGroupCalls(result.roomId);
+            return client.getRoom(result.roomId)!;
+          }
+
+          throw e;
+        }
       } else {
         // room IDs we just try to join by their ID, which will not work in the
         // general case without providing some servers to join via. We could provide