Flatten array arguments in legacyMode multi commands (#2064)

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

@@ -294,6 +294,20 @@ describe('Client', () => {
                 }
             }
         });
+
+        testUtils.testWithClient('client.multi.{command}.exec should flatten array arguments', async client => {
+            assert.deepEqual(
+                await client.multi()
+                    .sAdd('a', ['b', 'c'])
+                    .v4.exec(),
+                [2])
+        }, {
+            ...GLOBAL.SERVERS.OPEN,
+            clientOptions: {
+                legacyMode: true
+            }
+        });
+
     });
 
     describe('events', () => {

packages/client/lib/client/multi-command.ts

@@ -87,7 +87,7 @@ export default class RedisClientMultiCommand {
     #defineLegacyCommand(name: string): void {
         this.v4[name] = (this as any)[name].bind(this.v4);
         (this as any)[name] =
-            (...args: Array<unknown>): void => (this as any).addCommand(name, args);
+            (...args: Array<unknown>): void => (this as any).addCommand(name, ...args);
     }
 
     commandsExecutor(command: RedisCommand, args: Array<unknown>): this {