From 1584ab42c27cb95e1b142d811c47233348c8db0e Mon Sep 17 00:00:00 2001
From: Travis Ralston <travpc@gmail.com>
Date: Mon, 13 May 2019 14:12:58 -0600
Subject: [PATCH] Support a backup room ID in PermalinkCreator

In the case of room upgrades, it is possible the client is trying to render the room create event, but the user has never been in the old room. This results in an error because the PermalinkCreator cannot possibly figure out a room ID.

Instead, we'll feed the creator an alternate room ID to try if the room object can't be provided.

Fixes https://github.com/vector-im/riot-web/issues/9636
---
 src/components/views/messages/RoomCreate.js |  2 +-
 src/matrix-to.js                            | 15 +++++++++++----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/components/views/messages/RoomCreate.js b/src/components/views/messages/RoomCreate.js
index f9dc3df2dc..95254323fa 100644
--- a/src/components/views/messages/RoomCreate.js
+++ b/src/components/views/messages/RoomCreate.js
@@ -49,7 +49,7 @@ module.exports = React.createClass({
             return <div />; // We should never have been instaniated in this case
         }
         const prevRoom = MatrixClientPeg.get().getRoom(predecessor['room_id']);
-        const permalinkCreator = new RoomPermalinkCreator(prevRoom);
+        const permalinkCreator = new RoomPermalinkCreator(prevRoom, predecessor['room_id']);
         permalinkCreator.load();
         const predecessorPermalink = permalinkCreator.forEvent(predecessor['event_id']);
         return <div className="mx_CreateEvent">
diff --git a/src/matrix-to.js b/src/matrix-to.js
index a198bb422e..14467cb4c5 100644
--- a/src/matrix-to.js
+++ b/src/matrix-to.js
@@ -70,8 +70,12 @@ const MAX_SERVER_CANDIDATES = 3;
 // the list and magically have the link work.
 
 export class RoomPermalinkCreator {
-    constructor(room) {
+    // We support being given a roomId as a fallback in the event the `room` object
+    // doesn't exist or is not healthy for us to rely on. For example, loading a
+    // permalink to a room which the MatrixClient doesn't know about.
+    constructor(room, roomId=null) {
         this._room = room;
+        this._roomId = room ? room.roomId : roomId;
         this._highestPlUserId = null;
         this._populationMap = null;
         this._bannedHostsRegexps = null;
@@ -79,6 +83,10 @@ export class RoomPermalinkCreator {
         this._serverCandidates = null;
         this._started = false;
 
+        if (!this._roomId) {
+            throw new Error("Failed to resolve a roomId for the permalink creator to use");
+        }
+
         this.onMembership = this.onMembership.bind(this);
         this.onRoomState = this.onRoomState.bind(this);
     }
@@ -116,13 +124,13 @@ export class RoomPermalinkCreator {
     }
 
     forEvent(eventId) {
-        const roomId = this._room.roomId;
+        const roomId = this._roomId;
         const permalinkBase = `${baseUrl}/#/${roomId}/${eventId}`;
         return `${permalinkBase}${encodeServerCandidates(this._serverCandidates)}`;
     }
 
     forRoom() {
-        const roomId = this._room.roomId;
+        const roomId = this._roomId;
         const permalinkBase = `${baseUrl}/#/${roomId}`;
         return `${permalinkBase}${encodeServerCandidates(this._serverCandidates)}`;
     }
@@ -246,7 +254,6 @@ export class RoomPermalinkCreator {
     }
 }
 
-
 export function makeUserPermalink(userId) {
     return `${baseUrl}/#/${userId}`;
 }