Block read marker and read receipt from advancing into pending events

This changes the methods that update the read marker and read receipts to
prevent advancing into pending events.

Part of https://github.com/vector-im/riot-web/issues/9952

src/client.js

@@ -2148,7 +2148,12 @@ MatrixClient.prototype.sendReceipt = function(event, receiptType, callback) {
  * @return {module:client.Promise} Resolves: TODO
  * @return {module:http-api.MatrixError} Rejects: with an error response.
  */
-MatrixClient.prototype.sendReadReceipt = function(event, callback) {
+MatrixClient.prototype.sendReadReceipt = async function(event, callback) {
+    const eventId = event.getId();
+    const room = this.getRoom(event.getRoomId());
+    if (room && room.hasPendingEvent(eventId)) {
+        throw new Error(`Cannot set read receipt to a pending event (${eventId})`);
+    }
     return this.sendReceipt(event, "m.read", callback);
 };
 
@@ -2158,20 +2163,25 @@ MatrixClient.prototype.sendReadReceipt = function(event, callback) {
  * and displayed as a horizontal line in the timeline that is visually distinct to the
  * position of the user's own read receipt.
  * @param {string} roomId ID of the room that has been read
- * @param {string} eventId ID of the event that has been read
+ * @param {string} rmEventId ID of the event that has been read
  * @param {string} rrEvent the event tracked by the read receipt. This is here for
  * convenience because the RR and the RM are commonly updated at the same time as each
  * other. The local echo of this receipt will be done if set. Optional.
  * @return {module:client.Promise} Resolves: the empty object, {}.
  */
-MatrixClient.prototype.setRoomReadMarkers = function(roomId, eventId, rrEvent) {
-    const rmEventId = eventId;
-    let rrEventId;
+MatrixClient.prototype.setRoomReadMarkers = async function(roomId, rmEventId, rrEvent) {
+    const room = this.getRoom(roomId);
+    if (room && room.hasPendingEvent(rmEventId)) {
+        throw new Error(`Cannot set read marker to a pending event (${rmEventId})`);
+    }
 
     // Add the optional RR update, do local echo like `sendReceipt`
+    let rrEventId;
     if (rrEvent) {
         rrEventId = rrEvent.getId();
-        const room = this.getRoom(roomId);
+        if (room && room.hasPendingEvent(rrEventId)) {
+            throw new Error(`Cannot set read receipt to a pending event (${rrEventId})`);
+        }
         if (room) {
             room._addLocalEchoReceipt(this.credentials.userId, rrEvent, "m.read");
         }