fix(plugin-vue): use __vccOpts for vue-class-component

[borkeszmate]

Description

We use Vite with Vue 3 and Vue Class Component in class-style syntax.

Since vitejs/plugin-vue 1.8.1 version our apps broke with empty screen showing the following warning on the console: Component is missing template or render function.

The problem is linked to the _sfc_main variable located in packages/plugin-vue/src/main.ts.

Since class-style components utilize export default class {...} so that the value of the _sfc_main variable becomes the exported class itself, while using regular Vue component syntax it should be an object.

let scriptCode = `const _sfc_main = {}`
let map: RawSourceMap | SourceMap | undefined

const script = resolveScript(descriptor, options, ssr)

if (script) {
    // If the script is js/ts and has no external src, it can be directly placed
    // in the main module.
    if ((!script.lang || script.lang === 'ts') && !script.src) {
      scriptCode = compiler.rewriteDefault(
        script.content,
        '_sfc_main',
        script.lang === 'ts'
          ? ['typescript']
          : script.lang === 'tsx'
          ? ['typescript', 'jsx']
          : undefined
      )
      map = script.map
    } else {
      if (script.src) {
        await linkSrcToDescriptor(script.src, descriptor, pluginContext)
      }
      const src = script.src || descriptor.filename
      const langFallback = (script.src && path.extname(src).slice(1)) || 'js'
      const attrsQuery = attrsToQuery(script.attrs, langFallback)
      const srcQuery = script.src ? `&src` : ``
      const query = `?vue&type=script${srcQuery}${attrsQuery}`
      const request = JSON.stringify(src + query)
      scriptCode =
        `import _sfc_main from ${request}\n` + `export * from ${request}` // support named exports
    }

The freshly introduced helper function in packages/plugin-vue/src/helper.ts tries to set values on the _sfc_main variable (assuming it's an object, althougt in this case it's a class) declared in attachedProps like this:

export default (sfc, props) => {

  if (typeof sfc === 'function' ) {
    sfc = {};
  }

  for (const [key, val] of props) {
    sfc[key] = val
  }

  return sfc;
}

Since _sfc_main passed as an argument is a js class, properties are not set corrently. As render function is not present on _sfc_main, __VUE_HMR_RUNTIME__.createRecord(_sfc_main.__hmrId, _sfc_main) leads to HMR error causing an empty page.

This little PR modifies the helper function and checks if _sfc_main is a class and if so, it sets its value to and empty object, thus render function is set correctly.

Fixing this Vue Class Component related issue would be highly desired and appreciated by merging this PR or by other solution since most of our mid-sized projects rely on class based Vue.

Thank you!

Additional context

none

Reproduction

The malfunction can be easily reproduced from the following issue: #5352
or https://github.com/borkeszmate/vite-vue-plugin-bug (navigate to about)

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[calebeaires]

This is highly desired.

[borkeszmate]

@sodatea, please take it as a friendly enquiry. When could you take a quick look at this little PR? :)

[sodatea]

Please use __vccOpts as in https://github.com/vuejs/vue-loader/pull/1897/files

More context:
https://github.com/vuejs/vue-class-component/blob/70680d78ed61ac57f27ed193fc69c80d90faf4fe/src/vue.ts#L90-L95
https://github.com/vuejs/vue-next/blob/9e3d7731c7839638f49157123c6b372fec9e4d46/packages/runtime-core/src/hmr.ts#L74-L76

[alykamb]

Hi, thanks for the fix, will it take long to be deployed to npm?

[sodatea]

It's already in 2.7 beta.

[alykamb]

I meant the package plugin-vue, or these changes can be imported from vite directly as well?

[sodatea]

Oh sorry, I didn't realize that. It shall be available soon in the coming releases.