vitest-dev
diff --git a/‎packages/vitest/src/node/core.ts‎
Lines changed: 24 additions & 1 deletion b/‎packages/vitest/src/node/core.ts‎
Lines changed: 24 additions & 1 deletion
diff --git a/‎test/e2e/fixtures/pool/write-to-stdout-and-stderr.test.ts‎
Lines changed: 8 additions & 2 deletions b/‎test/e2e/fixtures/pool/write-to-stdout-and-stderr.test.ts‎
Lines changed: 8 additions & 2 deletions
diff --git a/‎test/e2e/test/watch/restart-coalescing.test.ts‎
Lines changed: 24 additions & 0 deletions b/‎test/e2e/test/watch/restart-coalescing.test.ts‎
Lines changed: 24 additions & 0 deletions
@@ -261,7 +261,30 @@ export class Vitest {
     )
   }
 
-  private async _restart(reason?: string) {
+  private _restartPromise?: Promise<void>
+  private _restartQueued = false
+
+  // Restarts must not overlap: chokidar regularly delivers several change
+  // events for one edit, and a restart that starts while another is still
+  // re-creating the servers reports `onServerRestart` to reporters that were
+  // re-instantiated but not yet initialized.
+  private _restart(reason?: string): Promise<void> {
+    if (this._restartPromise) {
+      this._restartQueued = true
+      return this._restartPromise
+    }
+    this._restartPromise = (async () => {
+      do {
+        this._restartQueued = false
+        await this._restartNow(reason)
+      } while (this._restartQueued)
+    })().finally(() => {
+      this._restartPromise = undefined
+    })
+    return this._restartPromise
+  }
+
+  private async _restartNow(reason?: string) {
     await Promise.all(this._onRestartListeners.map(fn => fn(reason)))
     this.report('onServerRestart', reason)
     await this.close()
 
@@ -1,11 +1,17 @@
 import { test } from 'vitest'
 import EventEmitter from 'node:events'
 
-test('write to streams', () => {
+test('write to streams', async () => {
   process.stdout.write('Worker writing to stdout')
   process.stderr.write('Worker writing to stderr')
 
+  // `emitWarning` prints to stderr asynchronously: without waiting for the
+  // event (plus one tick for the default handler's write), a fast worker
+  // teardown can exit before the warning reaches the captured stderr
+  const warning = new Promise<void>(resolve => process.once('warning', () => resolve()))
   triggerNodeWarning()
+  await warning
+  await new Promise(resolve => setImmediate(resolve))
 })
 
 function triggerNodeWarning() {
@@ -16,4 +22,4 @@ function triggerNodeWarning() {
   emitter.addListener('message', () => {})
 }
 
-class TestFixturesCustomEmitter extends EventEmitter {}
+class TestFixturesCustomEmitter extends EventEmitter {}
@@ -0,0 +1,24 @@
+import { runVitest } from '#test-utils'
+import { expect, test } from 'vitest'
+
+// chokidar regularly delivers several change events for one config edit, each
+// triggering a restart. A restart that begins while another is still
+// re-creating the servers used to report `onServerRestart` to reporters that
+// were re-instantiated but not yet initialized, crashing the run with
+// "Cannot read properties of undefined (reading 'logger')".
+test('concurrent restarts are coalesced instead of overlapping', async () => {
+  const { ctx, vitest } = await runVitest({
+    root: 'fixtures/watch',
+    watch: true,
+  })
+
+  const restart = (ctx as any)._restart.bind(ctx)
+  await Promise.all([restart('config'), restart('config'), restart('config')])
+
+  expect(vitest.stdout).toContain('Restarting due to config changes')
+  expect(vitest.stderr).not.toContain('Cannot read properties')
+
+  // the restarted instance is functional: a rerun still works
+  await ctx!.rerunFiles()
+  expect(vitest.stdout).toContain('RERUN')
+})