Fix #1870: TypeError in PubSub (#2016)

* Fix #1870: TypeError in PubSub

* Add test

This test is for a race condition; it should reliably pass now,
but is not guaranteed to fail with the previous version.

Author: jhiesey

packages/client/lib/client/commands-queue.ts

@@ -369,7 +369,8 @@ export default class RedisCommandsQueue {
     #setReturnBuffers() {
         this.#parser.setReturnBuffers(
             !!this.#waitingForReply.head?.value.returnBuffers ||
-            !!this.#pubSubState?.subscribed
+            !!this.#pubSubState?.subscribed ||
+            !!this.#pubSubState?.subscribing
         );
     }
 

packages/client/lib/client/index.spec.ts

@@ -683,6 +683,21 @@ describe('Client', () => {
             }
         }, GLOBAL.SERVERS.OPEN);
 
+        testUtils.testWithClient('should not fail when message arrives right after subscribe', async publisher => {
+            const subscriber = publisher.duplicate();
+
+            await subscriber.connect();
+
+            try {
+                await assert.doesNotReject(Promise.all([
+                    subscriber.subscribe('channel', () => {}),
+                    publisher.publish('channel', 'message')
+                ]));
+            } finally {
+                await subscriber.disconnect();
+            }
+        }, GLOBAL.SERVERS.OPEN);
+
         testUtils.testWithClient('should be able to quit in PubSub mode', async client => {
             await client.subscribe('channel', () => {
                 // noop