fix(pool): capture workers stdio to logger (#8809)

AriPerkkio · web-flow · commit fb95fc7360de · 2025-10-27T10:20:52.000+01:00
diff --git a/packages/vitest/src/node/pools/workers/forksWorker.ts b/packages/vitest/src/node/pools/workers/forksWorker.ts
@@ -1,4 +1,5 @@
 import type { ChildProcess } from 'node:child_process'
+import type { Writable } from 'node:stream'
 import type { SerializedConfig } from '../../types/config'
 import type { PoolOptions, PoolWorker, WorkerRequest } from '../types'
 import { fork } from 'node:child_process'
@@ -17,10 +18,15 @@ export class ForksPoolWorker implements PoolWorker {
   protected env: Partial<NodeJS.ProcessEnv>
 
   private _fork?: ChildProcess
+  private stdout: NodeJS.WriteStream | Writable
+  private stderr: NodeJS.WriteStream | Writable
 
   constructor(options: PoolOptions) {
     this.execArgv = options.execArgv
     this.env = options.env
+    this.stdout = options.project.vitest.logger.outputStream
+    this.stderr = options.project.vitest.logger.errorStream
+
     /** Loads {@link file://./../../../runtime/workers/forks.ts} */
     this.entrypoint = resolve(options.distPath, 'workers/forks.js')
   }
@@ -51,7 +57,18 @@ export class ForksPoolWorker implements PoolWorker {
     this._fork ||= fork(this.entrypoint, [], {
       env: this.env,
       execArgv: this.execArgv,
+      stdio: 'pipe',
     })
+
+    if (this._fork.stdout) {
+      this.stdout.setMaxListeners(1 + this.stdout.getMaxListeners())
+      this._fork.stdout.pipe(this.stdout)
+    }
+
+    if (this._fork.stderr) {
+      this.stderr.setMaxListeners(1 + this.stderr.getMaxListeners())
+      this._fork.stderr.pipe(this.stderr)
+    }
   }
 
   async stop(): Promise<void> {
@@ -80,6 +97,16 @@ export class ForksPoolWorker implements PoolWorker {
     await waitForExit
     clearTimeout(sigkillTimeout)
 
+    if (fork.stdout) {
+      fork.stdout?.unpipe(this.stdout)
+      this.stdout.setMaxListeners(this.stdout.getMaxListeners() - 1)
+    }
+
+    if (fork.stderr) {
+      fork.stderr?.unpipe(this.stderr)
+      this.stderr.setMaxListeners(this.stderr.getMaxListeners() - 1)
+    }
+
     this._fork = undefined
   }
 
diff --git a/packages/vitest/src/node/pools/workers/threadsWorker.ts b/packages/vitest/src/node/pools/workers/threadsWorker.ts
@@ -1,3 +1,4 @@
+import type { Writable } from 'node:stream'
 import type { PoolOptions, PoolWorker, WorkerRequest } from '../types'
 import { resolve } from 'node:path'
 import { Worker } from 'node:worker_threads'
@@ -11,10 +12,15 @@ export class ThreadsPoolWorker implements PoolWorker {
   protected env: Partial<NodeJS.ProcessEnv>
 
   private _thread?: Worker
+  private stdout: NodeJS.WriteStream | Writable
+  private stderr: NodeJS.WriteStream | Writable
 
   constructor(options: PoolOptions) {
     this.execArgv = options.execArgv
     this.env = options.env
+    this.stdout = options.project.vitest.logger.outputStream
+    this.stderr = options.project.vitest.logger.errorStream
+
     /** Loads {@link file://./../../../runtime/workers/threads.ts} */
     this.entrypoint = resolve(options.distPath, 'workers/threads.js')
   }
@@ -36,13 +42,27 @@ export class ThreadsPoolWorker implements PoolWorker {
     this._thread ||= new Worker(this.entrypoint, {
       env: this.env,
       execArgv: this.execArgv,
+      stdout: true,
+      stderr: true,
     })
+
+    this.stdout.setMaxListeners(1 + this.stdout.getMaxListeners())
+    this._thread.stdout.pipe(this.stdout)
+
+    this.stderr.setMaxListeners(1 + this.stderr.getMaxListeners())
+    this._thread.stderr.pipe(this.stderr)
   }
 
   async stop(): Promise<void> {
-    await this.thread.terminate().then(() => {
-      this._thread = undefined
-    })
+    await this.thread.terminate()
+
+    this._thread?.stdout?.unpipe(this.stdout)
+    this.stdout.setMaxListeners(this.stdout.getMaxListeners() - 1)
+
+    this._thread?.stderr?.unpipe(this.stderr)
+    this.stderr.setMaxListeners(this.stderr.getMaxListeners() - 1)
+
+    this._thread = undefined
   }
 
   deserialize(data: unknown): unknown {
diff --git a/test/config/fixtures/pool/write-to-stdout-and-stderr.test.ts b/test/config/fixtures/pool/write-to-stdout-and-stderr.test.ts
@@ -0,0 +1,19 @@
+import { test } from 'vitest'
+import EventEmitter from 'node:events'
+
+test('write to streams', () => {
+  process.stdout.write('Worker writing to stdout')
+  process.stderr.write('Worker writing to stderr')
+
+  triggerNodeWarning()
+})
+
+function triggerNodeWarning() {
+  const emitter = new TestFixturesCustomEmitter()
+  emitter.setMaxListeners(2)
+  emitter.addListener('message', () => {})
+  emitter.addListener('message', () => {})
+  emitter.addListener('message', () => {})
+}
+
+class TestFixturesCustomEmitter extends EventEmitter {}
diff --git a/test/config/test/console.test.ts b/test/config/test/console.test.ts
@@ -1,4 +1,4 @@
-import { expect, test, vi } from 'vitest'
+import { expect, test } from 'vitest'
 import { runVitest } from '../../test-utils'
 
 test('default intercept', async () => {
@@ -9,17 +9,13 @@ test('default intercept', async () => {
 })
 
 test.each(['threads', 'vmThreads'] as const)(`disable intercept pool=%s`, async (pool) => {
-  // `disableConsoleIntercept: true` forwards workers console.error to main thread's stderr
-  const spy = vi.spyOn(process.stderr, 'write').mockImplementation(() => true)
-
-  await runVitest({
+  const { stderr } = await runVitest({
     root: './fixtures/console',
     disableConsoleIntercept: true,
     pool,
   })
 
-  const call = spy.mock.lastCall![0]
-  expect(call.toString()).toBe('__test_console__\n')
+  expect(stderr).toBe('__test_console__\n')
 })
 
 test('group synchronous console logs', async () => {
diff --git a/test/config/test/node-sqlite.test.ts b/test/config/test/node-sqlite.test.ts
@@ -8,7 +8,7 @@ test.runIf(nodeMajor >= 22)('import node:sqlite', async () => {
     'vitest.config.ts': {
       test: {
         pool: 'forks',
-        execArgv: ['--experimental-sqlite'],
+        execArgv: ['--experimental-sqlite', '--no-warnings=ExperimentalWarning'],
       },
     },
     'basic.test.ts': ts`
diff --git a/test/config/test/pool.test.ts b/test/config/test/pool.test.ts
@@ -9,6 +9,18 @@ describe.each(['forks', 'threads', 'vmThreads', 'vmForks'])('%s', async (pool) =
 
     expect(config.pool).toBe(pool)
   })
+
+  test('can capture worker\'s stdout and stderr', async () => {
+    const { stdout, stderr } = await runVitest({
+      root: './fixtures/pool',
+      include: ['write-to-stdout-and-stderr.test.ts'],
+      pool,
+    })
+
+    expect(stderr).toContain('Worker writing to stderr')
+    expect(stdout).toContain('Worker writing to stdout')
+    expect(stderr).toContain('MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 3 message listeners added to [TestFixturesCustomEmitter]')
+  })
 })
 
 test('extended project inherits top-level pool related options', async () => {
diff --git a/test/coverage-test/vitest.config.ts b/test/coverage-test/vitest.config.ts
@@ -8,22 +8,16 @@ const UNIT_TESTS = 'test/**.unit.test.ts'
 const BROWSER_TESTS = 'test/**.browser.test.ts'
 const FIXTURES = '**/fixtures/**'
 
-const config = defineConfig({
-  test: {
-    pool: 'threads',
-    setupFiles: ['./setup.ts'],
-  },
-})
-
 export default defineConfig({
   test: {
     reporters: 'verbose',
     isolate: false,
+    setupFiles: ['./setup.ts'],
     projects: [
       // Test cases for v8-provider
       {
+        extends: true,
         test: {
-          ...config.test,
           name: { label: 'v8', color: 'green' },
           env: { COVERAGE_PROVIDER: 'v8' },
           include: [GENERIC_TESTS, V8_TESTS],
@@ -39,8 +33,8 @@ export default defineConfig({
 
       // Test cases for istanbul-provider
       {
+        extends: true,
         test: {
-          ...config.test,
           name: { label: 'istanbul', color: 'magenta' },
           env: { COVERAGE_PROVIDER: 'istanbul' },
           include: [GENERIC_TESTS, ISTANBUL_TESTS],
@@ -56,8 +50,8 @@ export default defineConfig({
 
       // Test cases for custom-provider
       {
+        extends: true,
         test: {
-          ...config.test,
           name: { label: 'custom', color: 'yellow' },
           env: { COVERAGE_PROVIDER: 'custom' },
           include: [CUSTOM_TESTS],
@@ -67,8 +61,8 @@ export default defineConfig({
 
       // Test cases for browser. Browser mode itself is activated by COVERAGE_BROWSER env var.
       {
+        extends: true,
         test: {
-          ...config.test,
           name: { label: 'istanbul-browser', color: 'blue' },
           env: { COVERAGE_PROVIDER: 'istanbul', COVERAGE_BROWSER: 'true' },
           testTimeout: 15_000,
@@ -98,8 +92,8 @@ export default defineConfig({
         },
       },
       {
+        extends: true,
         test: {
-          ...config.test,
           name: { label: 'v8-browser', color: 'red' },
           env: { COVERAGE_PROVIDER: 'v8', COVERAGE_BROWSER: 'true' },
           testTimeout: 15_000,
@@ -131,8 +125,8 @@ export default defineConfig({
 
       // Test cases that aren't provider specific
       {
+        extends: true,
         test: {
-          ...config.test,
           name: { label: 'unit', color: 'cyan' },
           include: [UNIT_TESTS],
           typecheck: {
