rpoplpush should rotate the list when source and destination are the same

[mgrunberg]

When same source and destination are provided rpoplpush should rotate the list. Instead, it is prepending the last element.

Code example:

const Redis = require("ioredis");
const RedisMock = require("ioredis-mock");
const assert = require("assert");

const redis = new Redis();
const redisMock = new RedisMock();

const testEquality = async () => {
  await redis.rpush("list", 1);
  await redis.rpush("list", 2);
  await redis.rpush("list", 3);
  await redisMock.rpush("list", 1);
  await redisMock.rpush("list", 2);
  await redisMock.rpush("list", 3);

  const pop = await redis.rpoplpush("list", "list");
  const popMock = await redisMock.rpoplpush("list", "list");

  const list = await redis.lrange("list", 0, -1);
  const listMock = await redisMock.lrange("list", 0, -1);

  await redis.flushall();
  await redisMock.flushall();
  await redis.quit();
  await redisMock.quit();

  assert(
    pop === popMock,
    `expected <${popMock.constructor.name}>(${popMock}) to equal <${pop.constructor.name}>(${pop})`
  );
  assert(
    list === listMock,
    `expected <${listMock.constructor.name}>(${listMock}) to equal <${list.constructor.name}>(${list})`
  );
  return "Success";
};

testEquality().then(console.log).catch(console.error);

Output:

AssertionError [ERR_ASSERTION]: expected <Array>(3,1,2,3) to equal <Array>(3,1,2)
    at testEquality (/home/matias/dev/workspace/ioredis-mock-example/index.js:31:3)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
  generatedMessage: false,
  code: 'ERR_ASSERTION',
  actual: false,
  expected: true,
  operator: '=='
}