fix: rpoplpush should rotate the list when source and destintation ar…

…e the same (#1321)

src/commands/rpoplpush.js

@@ -22,11 +22,18 @@ export function rpoplpush(source, destination) {
   const newSource = this.data.get(source)
   const item = newSource.pop()
 
-  const newDest = this.data.get(destination)
+  let newDest = newSource // Operate on the same list
+  if (source !== destination) {
+    // Operate on two different lists
+    newDest = this.data.get(destination)
+  }
+
   newDest.unshift(item)
 
   this.data.set(source, newSource)
-  this.data.set(destination, newDest)
+  if (newSource !== newDest) {
+    this.data.set(destination, newDest)
+  }
 
   return item
 }

test/integration/commands/rpoplpush.js

@@ -128,5 +128,23 @@ runTwinSuite('rpoplpush', (command, equals) => {
         )
       }
     )
+
+    // @TODO Rewrite test so it runs on a real Redis instance
+    ;(process.env.IS_E2E ? it.skip : it)(
+      'should rotate the list if the source and destination are the same',
+      async () => {
+        const redis = new Redis({
+          data: {
+            foo: ['1', '2'],
+          },
+        })
+
+        const result = await redis[command]('foo', 'foo', 'LEFT', 'RIGHT');
+        expect(result).toBe('2');
+
+        const list = await redis.lrange('foo', 0, -1)
+        expect(list).toEqual(['2', '1'])
+      }
+    )
   })
 })