fix(hmr): better fix for #610

Previous fix introduced a 100ms minimum delay for all HMR updates which
is very inefficient.

src/node/server/index.ts

@@ -66,11 +66,7 @@ export function createServer(config: ServerConfig): Server {
  const server = resolveServer(config, app.callback())
  const watcher = chokidar.watch(root, {
  ignored: ['**/node_modules/**', '**/.git/**'],
- // #610
- awaitWriteFinish: {
- stabilityThreshold: 100,
- pollInterval: 10
- },
+ ignoreInitial: true,
  ...chokidarWatchOptions
  }) as HMRWatcher
  const resolver = createResolver(root, resolvers, alias, assetsInclude)

src/node/server/serverPluginVue.ts

@@ -399,7 +399,7 @@ async function parseSFC(
 
  if (!content) {
  try {
- content = await cachedRead(null, filePath)
+ content = await cachedRead(null, filePath, true /* poll */)
  } catch (e) {
  return
  }

src/node/utils/fsUtils.ts

@@ -29,7 +29,8 @@ const fsReadCache = new LRUCache<string, CacheEntry>({
  */
 export async function cachedRead(
  ctx: Context | null,
- file: string
+ file: string,
+ poll = false
 ): Promise<Buffer> {
  const lastModified = fs.statSync(file).mtimeMs
  const cached = fsReadCache.get(file)
@@ -53,6 +54,10 @@ export async function cachedRead(
  }
  // #395 some file is an binary file, eg. font
  let content = await fs.readFile(file)
+ if (poll && !content.length) {
+ await untilModified(file)
+ content = await fs.readFile(file)
+ }
  // Populate the "sourcesContent" array and resolve relative paths in the
  // "sources" array, so the debugger can trace back to the original source.
  if (file.endsWith('.map')) {
@@ -106,6 +111,26 @@ export async function cachedRead(
  return content
 }
 
+// #610 when hot-reloading Vue files, we read immediately on file change event
+// and sometimes this can be too early and get an empty buffer. Poll until the
+// file's modified time has changed before reading again.
+async function untilModified(file: string) {
+ const mtime = (await fs.stat(file)).mtimeMs
+ return new Promise((r) => {
+ let n = 0
+ const poll = async () => {
+ n++
+ const newMtime = (await fs.stat(file)).mtimeMs
+ if (newMtime !== mtime || n > 10) {
+ r(0)
+ } else {
+ setTimeout(poll, 10)
+ }
+ }
+ setTimeout(poll, 10)
+ })
+}
+
 /**
  * Read already set body on a Koa context and normalize it into a string.
  * Useful in post-processing middlewares.