Fix legacyMode/pingInterval issue (#2386)

* Add a test for legacyMode pingInterval

* Apply patch to fix legacy mode ping interval

* use this.#sendCommand instead of this.#v4

Co-authored-by: Leibale <me@leibale.com>

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

@@ -341,6 +341,19 @@ describe('Client', () => {
                 legacyMode: true
             }
         });
+
+        testUtils.testWithClient('pingInterval', async client => {
+            assert.deepEqual(
+                await once(client, 'ping-interval'),
+                ['PONG']
+            );
+        }, {
+            ...GLOBAL.SERVERS.OPEN,
+            clientOptions: {
+                legacyMode: true,
+                pingInterval: 1
+            }
+        });
     });
 
     describe('events', () => {

packages/client/lib/client/index.ts

@@ -362,7 +362,8 @@ export default class RedisClient<
         this.#pingTimer = setTimeout(() => {
             if (!this.#socket.isReady) return;
 
-            (this as unknown as RedisClientType<M, F, S>).ping()
+            // using #sendCommand to support legacy mode
+            this.#sendCommand(['PING'])
                 .then(reply => this.emit('ping-interval', reply))
                 .catch(err => this.emit('error', err))
                 .finally(() => this.#setPingTimer());