feat!: support multiple parallel child_process

.github/workflows/ci.yml

@@ -81,8 +81,8 @@ jobs:
       - name: Test
         run: pnpm run test:ci
 
-      - name: Test Single Thread
-        run: pnpm run test:ci:single-thread
+      - name: Test No Threads
+        run: pnpm run test:ci:no-threads
 
       - name: Test Vm Threads
         run: pnpm run test:ci:vm-threads

docs/api/vi.md

@@ -704,8 +704,15 @@ unmockedIncrement(30) === 31
 
   To enable mocking timers, you need to call this method. It will wrap all further calls to timers (such as `setTimeout`, `setInterval`, `clearTimeout`, `clearInterval`, `nextTick`, `setImmediate`, `clearImmediate`, and `Date`), until [`vi.useRealTimers()`](#vi-userealtimers) is called.
 
+  Mocking `nextTick` is not supported when running Vitest inside `node:child_process` by using `--no-threads`. NodeJS uses `process.nextTick` internally in `node:child_process` and hangs when it is mocked. Mocking `nextTick` is supported when running Vitest with `--threads`.
+
   The implementation is based internally on [`@sinonjs/fake-timers`](https://github.com/sinonjs/fake-timers).
 
+  ::: tip
+  Since version `0.35.0` `vi.useFakeTimers()` no longer automatically mocks `process.nextTick`.
+  It can still be mocked by specyfing the option in `toFake` argument: `vi.useFakeTimers({ toFake: ['nextTick'] })`.
+  :::
+
 ## vi.isFakeTimers
 
 - **Type:** `() => boolean`

docs/config/index.md

@@ -692,7 +692,7 @@ Percentage based memory limit [does not work on Linux CircleCI](https://github.c
 
 Enable multi-threading using [tinypool](https://github.com/tinylibs/tinypool) (a lightweight fork of [Piscina](https://github.com/piscinajs/piscina)). Prior to Vitest 0.29.0, Vitest was still running tests inside worker thread, even if this option was disabled. Since 0.29.0, if this option is disabled, Vitest uses `child_process` to spawn a process to run tests inside, meaning you can use `process.chdir` and other API that was not available inside workers. If you want to revert to the previous behaviour, use `--single-thread` option instead.
 
-Disabling this option also disables module isolation, meaning all tests with the same environment are running inside a single child process.
+Disabling this option makes all tests run inside multiple child processes.
 
 ### singleThread
 

docs/guide/debugging.md

@@ -59,7 +59,7 @@ Vitest also supports debugging tests without IDEs. However this requires that te
 vitest --inspect-brk --single-thread
 
 # To run in a child process
-vitest --inspect-brk --no-threads
+vitest --inspect-brk  --single-thread --no-threads
 ```
 
 Once Vitest starts it will stop execution and waits for you to open developer tools that can connect to [NodeJS inspector](https://nodejs.org/en/docs/guides/debugging-getting-started/). You can use Chrome DevTools for this by opening `chrome://inspect` on browser.

package.json

@@ -24,7 +24,7 @@
     "test:all": "CI=true pnpm -r --stream run test --allowOnly",
     "test:ci": "CI=true pnpm -r --stream --filter !test-fails --filter !test-browser --filter !test-esm --filter !test-browser run test --allowOnly",
     "test:ci:vm-threads": "CI=true pnpm -r --stream --filter !test-fails --filter !test-single-thread --filter !test-browser --filter !test-esm --filter !test-browser run test --allowOnly --experimental-vm-threads",
-    "test:ci:single-thread": "CI=true pnpm -r --stream --filter !test-fails --filter !test-coverage --filter !test-watch --filter !test-bail --filter !test-esm --filter !test-browser run test --allowOnly --no-threads",
+    "test:ci:no-threads": "CI=true pnpm -r --stream --filter !test-fails --filter !test-coverage --filter !test-watch --filter !test-bail --filter !test-esm --filter !test-browser run test --allowOnly --no-threads",
     "typecheck": "tsc --noEmit",
     "typecheck:why": "tsc --noEmit --explainFiles > explainTypes.txt",
     "ui:build": "vite build packages/ui",

packages/ui/package.json

@@ -69,7 +69,7 @@
     "@vitest/ws-client": "workspace:*",
     "@vueuse/core": "^10.2.1",
     "ansi-to-html": "^0.7.2",
-    "birpc": "0.2.12",
+    "birpc": "0.2.14",
     "codemirror": "^5.65.13",
     "codemirror-theme-vars": "^0.1.2",
     "cypress": "^12.16.0",

packages/vitest/package.json

@@ -162,7 +162,7 @@
     "std-env": "^3.3.3",
     "strip-literal": "^1.0.1",
     "tinybench": "^2.5.0",
-    "tinypool": "^0.7.0",
+    "tinypool": "^0.8.1",
     "vite": "^3.1.0 || ^4.0.0 || ^5.0.0-0",
     "vite-node": "workspace:*",
     "why-is-node-running": "^2.2.2"
@@ -180,7 +180,7 @@
     "@types/micromatch": "^4.0.2",
     "@types/prompts": "^2.4.4",
     "@types/sinonjs__fake-timers": "^8.1.2",
-    "birpc": "0.2.12",
+    "birpc": "0.2.14",
     "chai-subset": "^1.6.0",
     "cli-truncate": "^3.1.0",
     "event-target-polyfill": "^0.0.3",

packages/vitest/src/api/setup.ts

@@ -21,7 +21,7 @@ export function setup(vitestOrWorkspace: Vitest | WorkspaceProject, server?: Vit
 
   const wss = new WebSocketServer({ noServer: true })
 
-  const clients = new Map<WebSocket, BirpcReturn<WebSocketEvents>>()
+  const clients = new Map<WebSocket, BirpcReturn<WebSocketEvents, WebSocketHandlers>>()
 
   ;(server || ctx.server).httpServer?.on('upgrade', (request, socket, head) => {
     if (!request.url)
@@ -154,7 +154,7 @@ class WebSocketReporter implements Reporter {
   constructor(
     public ctx: Vitest,
     public wss: WebSocketServer,
-    public clients: Map<WebSocket, BirpcReturn<WebSocketEvents>>,
+    public clients: Map<WebSocket, BirpcReturn<WebSocketEvents, WebSocketHandlers>>,
   ) {}
 
   onCollected(files?: File[]) {

packages/vitest/src/integrations/mock/timers.ts

@@ -130,7 +130,13 @@ export class FakeTimers {
     }
 
     if (!this._fakingTime) {
-      const toFake = Object.keys(this._fakeTimers.timers) as Array<keyof FakeTimerWithContext['timers']>
+      const toFake = Object.keys(this._fakeTimers.timers)
+        // Do not mock nextTick by default. It can still be mocked through userConfig.
+        .filter(timer => timer !== 'nextTick') as (keyof FakeTimerWithContext['timers'])[]
+
+      // @ts-expect-error -- untyped internal
+      if (this._userConfig?.toFake?.includes('nextTick') && globalThis.__vitest_worker__.isChildProcess)
+        throw new Error('process.nextTick cannot be mocked inside child_process')
 
       this._clock = this._fakeTimers.install({
         now: Date.now(),

packages/vitest/src/integrations/vi.ts

@@ -205,13 +205,21 @@ function createVitest(): VitestUtils {
 
   const utils: VitestUtils = {
     useFakeTimers(config?: FakeTimerInstallOpts) {
-      if (config) {
-        _timers.configure(config)
+      const workerState = getWorkerState()
+
+      if (workerState.isChildProcess) {
+        if (config?.toFake?.includes('nextTick') || workerState.config?.fakeTimers?.toFake?.includes('nextTick')) {
+          throw new Error(
+            'vi.useFakeTimers({ toFake: ["nextTick"] }) is not supported in node:child_process. Use --threads if mocking nextTick is required.',
+          )
+        }
       }
-      else {
-        const workerState = getWorkerState()
+
+      if (config)
+        _timers.configure(config)
+      else
         _timers.configure(workerState.config.fakeTimers)
-      }
+
       _timers.useFakeTimers()
       return utils
     },