Inlined CSS is not working in SSR after 2.9 release

[saurabhdaware]

Describe the bug

I have a setup where I write inlined CSS in index.html file. I expect this inlined CSS to work as it is in dev-server and it did work before 2.9 however after 2.9 the inlined CSS turns into something like this in the source -

<script type="module" src="/?html-proxy&amp;index=0.css"></script>

Apparently, it is happening during vite.transformIndexHtml API. It returns new HTML with proxy script instead of actual inlined css. Due to this the CSS is not applied during the dev-server.

The build continues to work fine.

Reproduction

https://stackblitz.com/edit/github-12zodn-vbxsug?file=index.html&terminal=dev

Exactly same example on Vite 2.8.6 - https://stackblitz.com/edit/github-12zodn-34x7n1?file=package.json&terminal=dev (works as expected)

System Info

System:
    OS: macOS 11.4
    CPU: (8) x64 Apple M1
    Memory: 520.12 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.5.0 - ~/.nvm/versions/node/v16.5.0/bin/node
    Yarn: 1.22.15 - ~/.yarn/bin/yarn
    npm: 7.19.1 - ~/.nvm/versions/node/v16.5.0/bin/npm
  Browsers:
    Brave Browser: 97.1.34.80
    Chrome: 100.0.4896.127
    Safari: 14.1.1

Used Package Manager

npm

Logs

/?html-proxy&index=0.css:1 Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of "text/html". Strict MIME type checking is enforced for module scripts per HTML spec.

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to https://github.com/vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[poyoho]

Thank you very much for your work to solve this issues. after my PR will return actual inlined css. But I use you repo can not find the issues what you said, can you help me to test it ?

[saurabhdaware]

Thank you very much for your work to solve this issues. after my PR will return actual inlined css. But I use you repo can not find the issues what you said, can you help me to test it ?

So I pulled your branch locally and tested out the changes there. They are working as expected. Your PR will resolve this issue 🕺🏼

[saurabhdaware]

Also created this github repo if you want to replicate it on your end https://github.com/saurabhdaware/vite-290-inlined-css-bug-replication

Added how to replicate in README