[jest-worker] Don't pass explicit env to new Worker when using worker_threads

packages/jest-worker/src/workers/NodeThreadsWorker.ts

@@ -60,10 +60,6 @@ export default class ExperimentalWorker implements WorkerInterface {
 
   initialize(): void {
     this._worker = new Worker(path.resolve(__dirname, './threadChild.js'), {
-      env: {
-        ...process.env,
-        JEST_WORKER_ID: String(this._options.workerId + 1), // 0-indexed workerId, 1-indexed JEST_WORKER_ID
-      },
       eval: false,
       // @ts-expect-error: added in newer versions
       resourceLimits: this._options.resourceLimits,
@@ -101,6 +97,7 @@ export default class ExperimentalWorker implements WorkerInterface {
       false,
       this._options.workerPath,
       this._options.setupArgs,
+      String(this._options.workerId + 1), // 0-indexed workerId, 1-indexed JEST_WORKER_ID
     ]);
 
     this._retries++;

packages/jest-worker/src/workers/__tests__/NodeThreadsWorker.test.js

@@ -70,7 +70,6 @@ it('passes fork options down to worker_threads.Worker, adding the defaults', ()
 
   expect(workerThreads.mock.calls[0][0]).toBe(thread.replace(/\.ts$/, '.js'));
   expect(workerThreads.mock.calls[0][1]).toEqual({
-    env: process.env, // Default option.
     eval: false,
     execArgv: ['--inspect', '-p'],
     execPath: 'hello', // Added option.
@@ -84,31 +83,21 @@ it('passes fork options down to worker_threads.Worker, adding the defaults', ()
   });
 });
 
-it('passes workerId to the thread and assign it to env.JEST_WORKER_ID', () => {
-  // eslint-disable-next-line no-new
-  new Worker({
-    forkOptions: {},
-    maxRetries: 3,
-    workerId: 2,
-    workerPath: '/tmp/foo',
-  });
-
-  expect(workerThreads.mock.calls[0][1].env.JEST_WORKER_ID).toEqual('3');
-});
-
-it('initializes the thread with the given workerPath', () => {
+it('initializes the thread with the given workerPath and workerId', () => {
   const worker = new Worker({
     forkOptions: {},
     maxRetries: 3,
     setupArgs: ['foo', 'bar'],
     workerPath: '/tmp/foo/bar/baz.js',
+    workerId: 2,
   });
 
   expect(worker._worker.postMessage.mock.calls[0][0]).toEqual([
     CHILD_MESSAGE_INITIALIZE,
     false,
     '/tmp/foo/bar/baz.js',
     ['foo', 'bar'],
+    '3'
   ]);
 });
 

packages/jest-worker/src/workers/__tests__/threadChild.test.js

@@ -128,6 +128,18 @@ afterEach(() => {
   thread.removeAllListeners('message');
 });
 
+it('sets env.JEST_WORKER_ID', () => {
+  thread.emit('message', [
+    CHILD_MESSAGE_INITIALIZE,
+    true, // Not really used here, but for flow type purity.
+    './my-fancy-worker',
+    [],
+    '3'
+  ]);
+
+  expect(process.env.JEST_WORKER_ID).toBe('3');
+})
+
 it('lazily requires the file', () => {
   expect(mockCount).toBe(0);
 

packages/jest-worker/src/workers/threadChild.ts

@@ -41,6 +41,7 @@ const messageListener = (request: any) => {
       const init: ChildMessageInitialize = request;
       file = init[2];
       setupArgs = request[3];
+      process.env.JEST_WORKER_ID = request[4];
       break;
 
     case CHILD_MESSAGE_CALL: