From 2e67b2b6b8ae1d82609369702df624bc1a8ec589 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Mon, 31 Aug 2020 14:21:18 +0200
Subject: [PATCH] handle prev_content location ambiguity

---
 src/matrix/room/common.js                     | 21 +++++++++++++++++++
 src/matrix/room/members/RoomMember.js         |  9 ++++----
 .../room/timeline/entries/EventEntry.js       |  3 ++-
 3 files changed, 28 insertions(+), 5 deletions(-)
 create mode 100644 src/matrix/room/common.js

diff --git a/src/matrix/room/common.js b/src/matrix/room/common.js
new file mode 100644
index 00000000..922ca115
--- /dev/null
+++ b/src/matrix/room/common.js
@@ -0,0 +1,21 @@
+/*
+Copyright 2020 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.
+*/
+
+export function getPrevContentFromStateEvent(event) {
+    // where to look for prev_content is a bit of a mess,
+    // see https://matrix.to/#/!NasysSDfxKxZBzJJoE:matrix.org/$DvrAbZJiILkOmOIuRsNoHmh2v7UO5CWp_rYhlGk34fQ?via=matrix.org&via=pixie.town&via=amorgan.xyz
+    return event.unsigned?.prev_content || event.prev_content;
+}
diff --git a/src/matrix/room/members/RoomMember.js b/src/matrix/room/members/RoomMember.js
index 0c05b4cb..c1c9f93b 100644
--- a/src/matrix/room/members/RoomMember.js
+++ b/src/matrix/room/members/RoomMember.js
@@ -1,5 +1,4 @@
 /*
-Copyright 2020 Bruno Windels <bruno@windels.cloud>
 Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
@@ -15,6 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import {getPrevContentFromStateEvent} from "../common.js";
+
 export const EVENT_TYPE = "m.room.member";
 
 export class RoomMember {
@@ -28,7 +29,7 @@ export class RoomMember {
             return;
         }
         const content = memberEvent.content;
-        const prevContent = memberEvent.unsigned?.prev_content;
+        const prevContent = getPrevContentFromStateEvent(memberEvent);
         const membership = content?.membership;
         // fall back to prev_content for these as synapse doesn't (always?)
         // put them on content for "leave" memberships
@@ -45,7 +46,7 @@ export class RoomMember {
         if (typeof userId !== "string") {
             return;
         }
-        const content = memberEvent.unsigned?.prev_content
+        const content = getPrevContentFromStateEvent(memberEvent);
         return this._validateAndCreateMember(roomId, userId,
             content?.membership,
             content?.displayname,
@@ -123,7 +124,7 @@ export class MemberChange {
     }
 
     previousMembership() {
-        return this._memberEvent.unsigned?.prev_content?.membership;
+        return getPrevContentFromStateEvent(this._memberEvent)?.membership;
     }
 
     membership() {
diff --git a/src/matrix/room/timeline/entries/EventEntry.js b/src/matrix/room/timeline/entries/EventEntry.js
index d1d5b64c..4dce9834 100644
--- a/src/matrix/room/timeline/entries/EventEntry.js
+++ b/src/matrix/room/timeline/entries/EventEntry.js
@@ -15,6 +15,7 @@ limitations under the License.
 */
 
 import {BaseEntry} from "./BaseEntry.js";
+import {getPrevContentFromStateEvent} from "../../common.js";
 
 export class EventEntry extends BaseEntry {
     constructor(eventEntry, fragmentIdComparer) {
@@ -35,7 +36,7 @@ export class EventEntry extends BaseEntry {
     }
 
     get prevContent() {
-        return this._eventEntry.event.unsigned?.prev_content;
+        return getPrevContentFromStateEvent(this._eventEntry.event);
     }
 
     get eventType() {