style not reload when change an import less file

[0x-jerry]

Describe the bug

when i change a import less file, for example part.less, and then save it. vite does not reload style.

main.js:

import 'style.less'

style.less:

@import './part.less'

part.less:

img {
  // when i change the next line and save it, the style does not update.
  border: 1px solid blue;
}

Reproduction

reproduce repo

1. clone repo
2. run npm install && npm run dev
3. open http://localhost:3000/
4. open src/part.less, change something and save it.

System Info

• required vite version: v1.0.0-beta.8
• required Operating System: macOS Catalina 10.15.5
• required Node version: v12.16.1
• Optional:
  • npm/yarn version
  • Installed vue version (from yarn.lock or package-lock.json)
  • Installed @vue/compiler-sfc version

Logs (Optional if provided reproduction)

1. Run vite or vite build with the --debug flag.
2. Provide the error log here.

  vite:rewrite (skipped) /src/index.css?import +4ms
  vite:rewrite (skipped) /src/style.less?import +40ms
  vite:rewrite (skipped) /src/style.less?import +3ms
  vite:rewrite (skipped) /src/index.css?import +1ms
  vite:rewrite (skipped) /src/assets/logo.png +10ms
  vite:rewrite (skipped) /src/assets/logo.png +11ms
  vite:rewrite /src/part.less: cache busted +3s
  vite:css part.less has changed, but it is not currently in use +0ms
  vite:rewrite /src/part.less: cache busted +969ms
  vite:css part.less has changed, but it is not currently in use +968ms

[underfin]

#313

[yyx990803]

Duplicate of #9