also decrypt all matching timeline entries when new key

src/matrix/room/Room.js

@@ -176,8 +176,20 @@ export class Room extends EventEmitter {
             let events = roomResponse?.timeline?.events || [];
             // when new keys arrive, also see if any events that can now be retried to decrypt
             if (newKeys) {
-                const nestedEntries = await Promise.all(newKeys.map(key => this._getRetryDecryptEntriesForKey(key, txn)));
+                const entriesPerKey = await Promise.all(newKeys.map(key => this._getRetryDecryptEntriesForKey(key, txn)));
-                retryEntries = nestedEntries.reduce((allEntries, entries) => allEntries.concat(entries), []);
+                retryEntries = entriesPerKey.reduce((allEntries, entries) => allEntries.concat(entries), []);
+                // If we have the timeline open, see if there are more entries for the new keys
+                // as we only store missing session for synced and not backfilled events.
+                // We want to decrypt all events we can though if the user is looking
+                // at them given the timeline is open
+                if (this._timeline) {
+                    let retryTimelineEntries = this._roomEncryption.filterEventEntriesForKeys(this._timeline.remoteEntries, newKeys);
+                    // filter out any entries already in retryEntries so we don't decrypt them twice
+                    const existingIds = new Set(retryEntries.map(e => e.id));
+                    retryTimelineEntries = retryTimelineEntries.filter(e => !existingIds.has(e.id))
+                    // make copies so we don't modify the original entry before the afterSync stage
+                    retryEntries = retryTimelineEntries.map(e => e.clone());
+                }
                 if (retryEntries.length) {
                     log.set("retry", retryEntries.length);
                     events = events.concat(retryEntries.map(entry => entry.event));

src/matrix/room/timeline/entries/EventEntry.js

@@ -25,6 +25,13 @@ export class EventEntry extends BaseEntry {
         this._decryptionResult = null;
     }
 
+    clone() {
+        const clone = new EventEntry(this._eventEntry, this._fragmentIdComparer);
+        clone._decryptionResult = this._decryptionResult;
+        clone._decryptionError = this._decryptionError;
+        return clone;
+    }
+
     get event() {
         return this._eventEntry.event;
     }