feat(dev): expose APIs for client-server communication

docs/guide/api-hmr.md

@@ -123,3 +123,11 @@ The following HMR events are dispatched by Vite automatically:
 - `'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.
+
+## `hot.send(event, data)`
+
+Send custom events back to Vite's dev server.
+
+If called before connected, the data will be buffered and sent once the connection is established.
+
+See [Client-server Communication](/guide/api-plugin.html#client-server-communication) for more details.

docs/guide/api-plugin.md

@@ -480,7 +480,7 @@ export default defineConfig({
 
 Check out [Vite Rollup Plugins](https://vite-rollup-plugins.patak.dev) for a list of compatible official Rollup plugins with usage instructions.
 
-## Path normalization
+## Path Normalization
 
 Vite normalizes paths while resolving ids to use POSIX separators ( / ) while preserving the volume in Windows. On the other hand, Rollup keeps resolved paths untouched by default, so resolved ids have win32 separators ( \\ ) in Windows. However, Rollup plugins use a [`normalizePath` utility function](https://github.com/rollup/plugins/tree/master/packages/pluginutils#normalizepath) from `@rollup/pluginutils` internally, which converts separators to POSIX before performing comparisons. This means that when these plugins are used in Vite, the `include` and `exclude` config pattern and other similar paths against resolved ids comparisons work correctly.
 
@@ -492,3 +492,71 @@ import { normalizePath } from 'vite'
 normalizePath('foo\\bar') // 'foo/bar'
 normalizePath('foo/bar') // 'foo/bar'
 ```
+
+## Client-server Communication
+
+Since Vite 2.9, we provide some utilities for plugins to help handle the communication with clients.
+
+### Server to Client
+
+On the plugin side, we could use `server.ws.send` to boardcast events to all the clients:
+
+```js
+// vite.config.js
+export default defineConfig({
+  plugins: [
+    {
+      // ...
+      configureServer(server) {
+        server.ws.send('my:greetings', { msg: 'hello' })
+      }
+    }
+  ]
+})
+```
+
+::: tip NOTE
+We recommend **alway prefixing** your event names to avoid collisions with other plugins.
+:::
+
+On the client side, use [`hot.on`](/guide/api-hmr.html#hot-on-event-cb) to listen to the events:
+
+```ts
+// client side
+if (import.meta.hot) {
+  import.meta.hot.on('my:greetings', (data) => {
+    console.log(data.msg) // hello
+  })
+}
+```
+
+### Client to Server
+
+To send events from the client to the server, we can use [`hot.send`](/guide/api-hmr.html#hot-send-event-payload):
+
+```ts
+// client side
+if (import.meta.hot) {
+  import.meta.hot.send('my:from-client', { msg: 'Hey!' })
+}
+```
+
+Then use `server.ws.on` and listen to the events on the server side:
+
+```js
+// vite.config.js
+export default defineConfig({
+  plugins: [
+    {
+      // ...
+      configureServer(server) {
+        server.ws.on('my:from-client', (data, client) => {
+          console.log('Message from client:', data.msg) // Hey!
+          // reply only to the client (if needed)
+          client.send('my:ack', { msg: 'Hi! I got your message!' })
+        })
+      }
+    }
+  ]
+})
+```

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

@@ -123,11 +123,16 @@ if (!isBuild) {
     await untilUpdated(() => el.textContent(), 'edited')
   })
 
+  test('plugin client-server communication', async () => {
+    const el = await page.$('.custom-communication')
+    await untilUpdated(() => el.textContent(), '3')
+  })
+
   test('full-reload encodeURI path', async () => {
     await page.goto(
       viteTestUrl + '/unicode-path/中文-にほんご-한글-🌕🌖🌗/index.html'
     )
-    let el = await page.$('#app')
+    const el = await page.$('#app')
     expect(await el.textContent()).toBe('title')
     await editFile(
       'unicode-path/中文-にほんご-한글-🌕🌖🌗/index.html',

packages/playground/hmr/hmr.js

@@ -57,6 +57,12 @@ if (import.meta.hot) {
   import.meta.hot.on('foo', ({ msg }) => {
     text('.custom', msg)
   })
+
+  // send custom event to server to calculate 1 + 2
+  import.meta.hot.send('remote-add', { a: 1, b: 2 })
+  import.meta.hot.on('remote-add-result', ({ result }) => {
+    text('.custom-communication', result)
+  })
 }
 
 function text(el, text) {

packages/playground/hmr/index.html

@@ -5,5 +5,6 @@
 <div class="dep"></div>
 <div class="nested"></div>
 <div class="custom"></div>
+<div class="custom-communication"></div>
 <div class="css-prev"></div>
 <div class="css-post"></div>

packages/playground/hmr/vite.config.js

@@ -9,14 +9,13 @@ module.exports = {
         if (file.endsWith('customFile.js')) {
           const content = await read()
           const msg = content.match(/export const msg = '(\w+)'/)[1]
-          server.ws.send({
-            type: 'custom',
-            event: 'foo',
-            data: {
-              msg
-            }
-          })
+          server.ws.send('foo', { msg })
         }
+      },
+      configureServer(server) {
+        server.ws.on('remote-add', ({ a, b }, client) => {
+          client.send('remote-add-result', { result: a + b })
+        })
       }
     }
   ]

packages/vite/src/client/client.ts

@@ -30,6 +30,7 @@ const socketHost = __HMR_PORT__
 
 const socket = new WebSocket(`${socketProtocol}://${socketHost}`, 'vite-hmr')
 const base = __BASE__ || '/'
+const messageBuffer: string[] = []
 
 function warnFailedFetch(err: Error, path: string | string[]) {
   if (!err.message.match('fetch')) {
@@ -59,9 +60,10 @@ async function handleMessage(payload: HMRPayload) {
   switch (payload.type) {
     case 'connected':
       console.log(`[vite] connected.`)
+      sendMessageBuffer()
       // proxy(nginx, docker) hmr ws maybe caused timeout,
       // so send ping package let ws keep alive.
-      setInterval(() => socket.send('ping'), __HMR_TIMEOUT__)
+      setInterval(() => socket.send('{"type":"ping"}'), __HMR_TIMEOUT__)
       break
     case 'update':
       notifyListeners('vite:beforeUpdate', payload)
@@ -361,6 +363,13 @@ async function fetchUpdate({ path, acceptedPath, timestamp }: Update) {
   }
 }
 
+function sendMessageBuffer() {
+  if (socket.readyState === 1) {
+    messageBuffer.forEach((msg) => socket.send(msg))
+    messageBuffer.length = 0
+  }
+}
+
 interface HotModule {
   id: string
   callbacks: HotCallback[]
@@ -478,6 +487,11 @@ export const createHotContext = (ownerPath: string) => {
       }
       addToMap(customListenersMap)
       addToMap(newListeners)
+    },
+
+    send: (event: string, data?: any) => {
+      messageBuffer.push(JSON.stringify({ type: 'custom', event, data }))
+      sendMessageBuffer()
     }
   }
 

packages/vite/src/node/index.ts

@@ -73,7 +73,11 @@ export type { TransformOptions as EsbuildTransformOptions } from 'esbuild'
 export type { ESBuildOptions, ESBuildTransformResult } from './plugins/esbuild'
 export type { Manifest, ManifestChunk } from './plugins/manifest'
 export type { ResolveOptions, InternalResolveOptions } from './plugins/resolve'
-export type { WebSocketServer } from './server/ws'
+export type {
+  WebSocketServer,
+  WebSocketClient,
+  WebSocketCustomListener
+} from './server/ws'
 export type { PluginContainer } from './server/pluginContainer'
 export type { ModuleGraph, ModuleNode, ResolvedUrl } from './server/moduleGraph'
 export type { SendOptions } from './server/send'