Jest: Different behaviour when using util.promisify

[Dreamacro]

Do you want to request a feature or report a bug?

bug

What is the current behavior?

test('should return 1', async () => {
  const fd = await open('src', 'r')

  const buffer = Buffer.alloc(1)

  const { bytesRead } = await read(fd, buffer, 0, 1, 0)

  expect(bytesRead).toEqual(1)
})

Received: undefined

If the current behavior is a bug, please provide the steps to reproduce and either a repl.it demo through https://repl.it/languages/jest or a minimal repository on GitHub that we can yarn install and yarn test.

https://repl.it/KR7e

What is the expected behavior?

Receive 1 instead of undefined

node.js doc

If this method is invoked as its util.promisify()ed version, it returns a Promise for an object with bytesRead and buffer properties.

Please provide your exact Jest configuration and mention your Jest, node, yarn/npm version and operating system.

Jest is 20.0.4. Node: 8.4.0, Npm: 5.3.0, OS: macOS Sierra

[zsxsoft]

Node 8.1.3, Windows 10 x64, Jest 20.0.4, reproduced.

[aikoven]

Caused by https://github.com/isaacs/node-graceful-fs/issues/125

[evantahler]

For now, it would be helpful to throw a warning that util.promisify may not function properly in jest tests...

[Rokt33r]

Similar issue here. https://github.com/sindresorhus/got/issues/811

[SimenB]

The reproduction in the repl.it in the OP does not reproduce the wrong behavior on the latest version of Jest. The test now fails with this error, which seems expected?:

The linked issue from got works fine if I remove micro, which I've never heard of and have no idea what does. And it just times out if I do not remove it, it doesn't fail like the linked issue says it does

Can someone put together a reproduction that fails with Jest 24.8.0?

[Rokt33r]

Deleting micro doesn't work for me. I'm using [email protected] and [email protected].

[Rokt33r]

And I don't think micro causes the problem. It just handles several cases that its request handler is returning or throwing something without calling res.end. https://github.com/zeit/micro/blob/master/packages/micro/lib/index.js#L25

[SimenB]

Can you put together a reproduction I can pull down and run?

[SimenB]

Oh, make sure you are using the node environment, and not the jsdom one: https://jestjs.io/docs/en/configuration#testenvironment-string

[Rokt33r]

I'm using node env.

{
    "preset": "ts-jest",
    "testEnvironment": "node",
    "testPathIgnorePatterns": [
      "/node_modules/",
      "/dist/"
    ]
}

I'll make a repo soon.

[Rokt33r]

@SimenB https://github.com/Rokt33r/jest-repro-promisify Sorry for being late.

[Rokt33r]

@SimenB Ping.

[SimenB]

@Rokt33r your issue is #2549. In particular this line is false meaning the callback passed as options is not assigned to cb.

I opened up https://github.com/salesforce/tough-cookie/pull/158 which fixes the issue and makes your test work correctly in Jest.

---

util.promisify works correctly, so I'll close this issue