MessageReceiver: Don't wait for app logic to start next decrypt

libtextsecure/message_receiver.js

@@ -224,7 +224,11 @@ MessageReceiver.prototype.extend({
     window.log.error('websocket error');
   },
   dispatchAndWait(event) {
-    return Promise.all(this.dispatchEvent(event));
+    const promise = this.appPromise || Promise.resolve();
+    const appJobPromise = Promise.all(this.dispatchEvent(event));
+    const job = () => appJobPromise;
+
+    this.appPromise = promise.then(job, job);
   },
   onclose(ev) {
     window.log.info(
@@ -354,23 +358,34 @@ MessageReceiver.prototype.extend({
     const { incoming } = this;
     this.incoming = [];
 
-    const dispatchEmpty = () => {
+    const emitEmpty = () => {
       window.log.info("MessageReceiver: emitting 'empty' event");
       const ev = new Event('empty');
-      return this.dispatchAndWait(ev);
+      this.dispatchAndWait(ev);
+    };
+
+    const waitForApplication = async () => {
+      window.log.info(
+        "MessageReceiver: finished processing messages after 'empty', now waiting for application"
+      );
+      const promise = this.appPromise || Promise.resolve();
+      this.appPromise = Promise.resolve();
+
+      // We don't await here because we don't this to gate future message processing
+      promise.then(emitEmpty, emitEmpty);
     };
 
-    const queueDispatch = () => {
+    const waitForEmptyQueue = () => {
       // resetting count to zero so everything queued after this starts over again
       this.count = 0;
 
-      this.addToQueue(dispatchEmpty);
+      this.addToQueue(waitForApplication);
     };
 
     // We first wait for all recently-received messages (this.incoming) to be queued,
-    //   then we add a task to emit the 'empty' event to the queue, so all message
-    //   processing is complete by the time it runs.
-    Promise.all(incoming).then(queueDispatch, queueDispatch);
+    //   then we queue a task to wait for the application to finish its processing, then
+    //   finally we emit the 'empty' event to the queue.
+    Promise.all(incoming).then(waitForEmptyQueue, waitForEmptyQueue);
   },
   drain() {
     const { incoming } = this;