feat: add client events to import.meta.hot.on

docs/guide/api-hmr.md

@@ -112,4 +112,13 @@ For now, calling `import.meta.hot.invalidate()` simply reloads the page.
 
 ## `hot.on(event, cb)`
 
-Listen to a custom HMR event. Custom HMR events can be sent from plugins. See [handleHotUpdate](./api-plugin#handlehotupdate) for more details.
+Listen to an HMR event.
+
+The following HMR events are dispatched by Vite automatically:
+- `'vite:beforeUpdate'` when an update is about to be applied (e.g. a module will be replaced)
+- `'vite:beforeFullReload'` when a full reload is about to occur
+- `'vite:beforePrune'` when modules that are no longer needed are about to be pruned
+- `'vite:error'` when an error occurs (e.g. syntax error)
+
+Custom HMR events can also be sent from plugins. See [handleHotUpdate](./api-plugin#handlehotupdate) for more details.
+

packages/playground/hmr/__tests__/hmr.spec.ts

@@ -20,6 +20,7 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), '2')
 
     expect(browserLogs).toMatchObject([
+      '>>> vite:beforeUpdate -- update',
       'foo was: 1',
       '(self-accepting 1) foo is now: 2',
       '(self-accepting 2) foo is now: 2',
@@ -31,6 +32,7 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), '3')
 
     expect(browserLogs).toMatchObject([
+      '>>> vite:beforeUpdate -- update',
       'foo was: 2',
       '(self-accepting 1) foo is now: 3',
       '(self-accepting 2) foo is now: 3',
@@ -48,6 +50,7 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), '2')
 
     expect(browserLogs).toMatchObject([
+      '>>> vite:beforeUpdate -- update',
       '(dep) foo was: 1',
       '(dep) foo from dispose: 1',
       '(single dep) foo is now: 2',
@@ -64,6 +67,7 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), '3')
 
     expect(browserLogs).toMatchObject([
+      '>>> vite:beforeUpdate -- update',
       '(dep) foo was: 2',
       '(dep) foo from dispose: 2',
       '(single dep) foo is now: 3',
@@ -84,6 +88,7 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), '2')
 
     expect(browserLogs).toMatchObject([
+      '>>> vite:beforeUpdate -- update',
       '(dep) foo was: 3',
       '(dep) foo from dispose: 3',
       '(single dep) foo is now: 3',
@@ -100,6 +105,7 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), '3')
 
     expect(browserLogs).toMatchObject([
+      '>>> vite:beforeUpdate -- update',
       '(dep) foo was: 3',
       '(dep) foo from dispose: 3',
       '(single dep) foo is now: 3',

packages/playground/hmr/hmr.js

@@ -33,6 +33,14 @@ if (import.meta.hot) {
     console.log(`foo was:`, foo)
   })
 
+  import.meta.hot.on('vite:beforeUpdate', (event) => {
+    console.log(`>>> vite:beforeUpdate -- ${event.type}`)
+  })
+
+  import.meta.hot.on('vite:error', (event) => {
+    console.log(`>>> vite:error -- ${event.type}`)
+  })
+
   import.meta.hot.on('foo', ({ msg }) => {
     text('.custom', msg)
   })

packages/vite/client.d.ts

@@ -1,5 +1,13 @@
 /// <reference lib="dom" />
 
+import {
+  ConnectedPayload,
+  ErrorPayload,
+  FullReloadPayload,
+  PrunePayload,
+  UpdatePayload
+} from 'types/hmrPayload'
+
 interface ImportMeta {
   url: string
 
@@ -20,7 +28,19 @@ interface ImportMeta {
     decline(): void
     invalidate(): void
 
-    on(event: string, cb: (...args: any[]) => void): void
+    on: {
+      (event: 'vite:beforeUpdate', cb: (payload: UpdatePayload) => void): void
+      (event: 'vite:beforePrune', cb: (payload: PrunePayload) => void): void
+      (
+        event: 'vite:beforeFullReload',
+        cb: (payload: FullReloadPayload) => void
+      ): void
+      (event: 'vite:error', cb: (payload: ErrorPayload) => void): void
+      <T extends string>(
+        event: CustomEventName<T>,
+        cb: (data: any) => void
+      ): void
+    }
   }
 
   readonly env: ImportMetaEnv
@@ -47,6 +67,10 @@ interface ImportMetaEnv {
   PROD: boolean
 }
 
+// See https://stackoverflow.com/a/63549561.
+type CustomEventName<T extends string> = (T extends `vite:${T}` ? never : T) &
+  (`vite:${T}` extends T ? never : T)
+
 // CSS modules
 type CSSModuleClasses = { readonly [key: string]: string }
 

packages/vite/src/client/client.ts

@@ -1,6 +1,15 @@
-import { ErrorPayload, HMRPayload, Update } from 'types/hmrPayload'
+import {
+  ConnectedPayload,
+  ErrorPayload,
+  FullReloadPayload,
+  HMRPayload,
+  PrunePayload,
+  Update,
+  UpdatePayload
+} from 'types/hmrPayload'
 import { ErrorOverlay, overlayId } from './overlay'
 import './env'
+
 // injected by the hmr plugin when served
 declare const __ROOT__: string
 declare const __BASE__: string
@@ -46,6 +55,7 @@ async function handleMessage(payload: HMRPayload) {
       setInterval(() => socket.send('ping'), __HMR_TIMEOUT__)
       break
     case 'update':
+      notifyListeners('vite:beforeUpdate', payload)
       // if this is the first update and there's already an error overlay, it
       // means the page opened with existing server compile error and the whole
       // module script failed to load (since one of the nested imports is 500).
@@ -84,13 +94,11 @@ async function handleMessage(payload: HMRPayload) {
       })
       break
     case 'custom': {
-      const cbs = customListenersMap.get(payload.event)
-      if (cbs) {
-        cbs.forEach((cb) => cb(payload.data))
-      }
+      notifyListeners(payload.event as CustomEventName<any>, payload.data)
       break
     }
     case 'full-reload':
+      notifyListeners('vite:beforeFullReload', payload)
       if (payload.path && payload.path.endsWith('.html')) {
         // if html file is edited, only reload the page if the browser is
         // currently on that page.
@@ -108,6 +116,7 @@ async function handleMessage(payload: HMRPayload) {
       }
       break
     case 'prune':
+      notifyListeners('vite:beforePrune', payload)
       // After an HMR update, some modules are no longer imported on the page
       // but they may have left behind side effects that need to be cleaned up
       // (.e.g style injections)
@@ -120,6 +129,7 @@ async function handleMessage(payload: HMRPayload) {
       })
       break
     case 'error': {
+      notifyListeners('vite:error', payload)
       const err = payload.err
       if (enableOverlay) {
         createErrorOverlay(err)
@@ -135,6 +145,31 @@ async function handleMessage(payload: HMRPayload) {
   }
 }
 
+function notifyListeners(
+  event: 'vite:beforeUpdate',
+  payload: UpdatePayload
+): void
+function notifyListeners(event: 'vite:beforePrune', payload: PrunePayload): void
+function notifyListeners(
+  event: 'vite:beforeFullReload',
+  payload: FullReloadPayload
+): void
+function notifyListeners(event: 'vite:error', payload: ErrorPayload): void
+function notifyListeners<T extends string>(
+  event: CustomEventName<T>,
+  data: any
+): void
+function notifyListeners(event: string, data: any): void {
+  const cbs = customListenersMap.get(event)
+  if (cbs) {
+    cbs.forEach((cb) => cb(data))
+  }
+}
+
+// See https://stackoverflow.com/a/63549561.
+type CustomEventName<T extends string> = (T extends `vite:${T}` ? never : T) &
+  (`vite:${T}` extends T ? never : T)
+
 const enableOverlay = __HMR_ENABLE_OVERLAY__
 
 function createErrorOverlay(err: ErrorPayload['err']) {
@@ -331,10 +366,10 @@ const hotModulesMap = new Map<string, HotModule>()
 const disposeMap = new Map<string, (data: any) => void | Promise<void>>()
 const pruneMap = new Map<string, (data: any) => void | Promise<void>>()
 const dataMap = new Map<string, any>()
-const customListenersMap = new Map<string, ((customData: any) => void)[]>()
+const customListenersMap = new Map<string, ((data: any) => void)[]>()
 const ctxToListenersMap = new Map<
   string,
-  Map<string, ((customData: any) => void)[]>
+  Map<string, ((data: any) => void)[]>
 >()
 
 // Just infer the return type for now
@@ -425,7 +460,7 @@ export const createHotContext = (ownerPath: string) => {
     },
 
     // custom events
-    on(event: string, cb: () => void) {
+    on: (event: string, cb: (data: any) => void) => {
       const addToMap = (map: Map<string, any[]>) => {
         const existing = map.get(event) || []
         existing.push(cb)