JEST_WORKER_ID starts with 0.

[dexterleng]

🐛 Bug Report

JEST_WORKER_ID starts from 0 instead of 1 specified here:

Note: Each worker has a unique id (index that starts with 1) which is available on process.env.JEST_WORKER_ID

https://github.com/facebook/jest/blob/master/packages/jest-worker/README.md

To Reproduce

Its on a private repo. I have tried reproducing it on a public repo but I couldn't get it to work.

I have two .spec.ts files with the same content:

import knex from "knex";
import { createTestConnection } from "../test-utils/createTestConnection";
import { clearDatabase } from "../test-utils/clearDatabase";

var testConnection: knex;
beforeAll(async (done) => {
  console.log(process.env.JEST_WORKER_ID);
  const connection = await createTestConnection(process.env.JEST_WORKER_ID);
  testConnection = connection;
  done();
});

afterEach(async (done) => {
  await clearDatabase(testConnection);
  done();
});

afterAll((done) => {
  testConnection.destroy(() => {
    done();
  });
});

test("quick maffs", async done => {
  expect(1 + 1).toEqual(2);
  done();
});

0 and 1 is printed.

Expected behavior

1 and 2 to be printed.

[dexterleng]

Ok turns out I couldn't not reproduce because I was using CRA and react-scripts jest just is a bit behind ("23.6.0",). To reproduce just console.log(JEST_WORKER_ID) in any jest project.

[jeysal]

Thanks for reporting, I'll take a look.

[natealcedo]

The way we instantiate workers now is different.

The original implementation assigned workers in a for loop and assigning id as i + 1.
https://github.com/facebook/jest/pull/5494/files#diff-61ba9f2c3304466545bec864a68f863d

Where as here we now have.
https://github.com/facebook/jest/blob/master/packages/jest-worker/src/base/BaseWorkerPool.ts#L41

I've tested this locally and this only occurs when the tests are ran in parallel.
Running tests in band correctly assigns the id to 1

Small regression that happened during the migration to typescript

[jeysal]

Yes, I noticed that. This used to work (and still does for runInBand).
I first wanted to convert workerIds everywhere to 1-indexed, but that touches many places and is quite unintuitive. TBH I don't really understand why it was ever 1-indexed (especially given that the 0 is not used for in band runs as suggested in the original PR). I'll now just make process.env.JEST_WORKER_ID be workerId + 1 I guess.

[github-actions]

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