fix: exclude queueMicrotask from default fake timers to not break node fetch (#7505)

Author: hi-ogawa

docs/api/vi.md

@@ -818,8 +818,8 @@ Mocking `nextTick` is not supported when running Vitest inside `node:child_proce
 The implementation is based internally on [`@sinonjs/fake-timers`](https://github.com/sinonjs/fake-timers).
 
 ::: tip
-`vi.useFakeTimers()` does not automatically mock `process.nextTick`.
-But you can enable it by specifying the option in `toFake` argument: `vi.useFakeTimers({ toFake: ['nextTick'] })`.
+`vi.useFakeTimers()` does not automatically mock `process.nextTick` and `queueMicrotask`.
+But you can enable it by specifying the option in `toFake` argument: `vi.useFakeTimers({ toFake: ['nextTick', 'queueMicrotask'] })`.
 :::
 
 ### vi.isFakeTimers {#vi-isfaketimers}

docs/config/index.md

@@ -2345,7 +2345,7 @@ Installs fake timers with the specified Unix epoch.
 #### fakeTimers.toFake
 
 - **Type:** `('setTimeout' | 'clearTimeout' | 'setImmediate' | 'clearImmediate' | 'setInterval' | 'clearInterval' | 'Date' | 'nextTick' | 'hrtime' | 'requestAnimationFrame' | 'cancelAnimationFrame' | 'requestIdleCallback' | 'cancelIdleCallback' | 'performance' | 'queueMicrotask')[]`
-- **Default:** everything available globally except `nextTick`
+- **Default:** everything available globally except `nextTick` and `queueMicrotask`
 
 An array with names of global methods and APIs to fake.
 

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

@@ -153,9 +153,9 @@ export class FakeTimers {
 
     if (!this._fakingTime) {
       const toFake = Object.keys(this._fakeTimers.timers)
-        // Do not mock nextTick by default. It can still be mocked through userConfig.
+        // Do not mock timers internally used by node by default. It can still be mocked through userConfig.
         .filter(
-          timer => timer !== 'nextTick',
+          timer => timer !== 'nextTick' && timer !== 'queueMicrotask',
         ) as (keyof FakeTimerWithContext['timers'])[]
 
       if (this._userConfig?.toFake?.includes('nextTick') && isChildProcess()) {

test/core/test/timers-queueMicrotask.test.ts

@@ -0,0 +1,27 @@
+import { expect, onTestFinished, test, vi } from 'vitest'
+
+test(`node fetch works without fake timers`, async () => {
+  expect(await Response.json('ok').json()).toBe('ok')
+})
+
+test(`node fetch works with fake timers`, async () => {
+  vi.useFakeTimers()
+  onTestFinished(() => {
+    vi.useRealTimers()
+  })
+  expect(await Response.json('ok').json()).toBe('ok')
+})
+
+// skipped since this might cause a weird OOM on CI
+test.skip(`node fetch timeouts with fake queueMicrotask`, async () => {
+  vi.useFakeTimers({ toFake: ['queueMicrotask'] })
+  onTestFinished(() => {
+    vi.useRealTimers()
+  })
+  expect(
+    await Promise.race([
+      new Promise(r => setTimeout(() => r('timeout'), 200)),
+      Response.json('ok').json(),
+    ]),
+  ).toBe('timeout')
+})