Using the swr package breaks CSS injection in UMD

[binary-koan]

Describe the bug

I'm attempting to use the swr package in a Vite app, which is being built as UMD and embedded into another site.

I expect this to just work, but adding swr causes the CSS not to be included correctly in the UMD bundle. This means when the app is embedded the CSS isn't loaded and everything appears unstyled.

Reproduction

https://stackblitz.com/edit/vitejs-vite-px4o6w

Steps to reproduce

Since this is a problem in the UMD build, you can reproduce with:

npm run build
npm run serve

The default template CSS is still being imported, but is not activated so the page appears unstyled. If you comment out the SWR import then the CSS works correctly.

(index.html adjusted to load the UMD build instead of being the Vite entry point)

This seems to be because Vite is looking for the string execute: to insert the CSS after it. For UMD this is normally not found so the CSS is injected at the top, but since SWR happens to have this string in a comment in the middle of the library the CSS gets injected inside this function instead - meaning it isn't executed when the page loads.

System Info

System:
    OS: macOS 13.3.1
    CPU: (10) arm64 Apple M2 Pro
    Memory: 80.53 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 18.16.0 - ~/.nvm/versions/node/v18.16.0/bin/node
    Yarn: 1.22.19 - ~/.yarn/bin/yarn
    npm: 9.5.1 - ~/.nvm/versions/node/v18.16.0/bin/npm
    Watchman: 2023.05.08.00 - /opt/homebrew/bin/watchman
  Browsers:
    Chrome: 114.0.5735.198
    Edge: 114.0.1823.58
    Firefox: 113.0.2
    Safari: 16.4

Used Package Manager

yarn

Logs

No response

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• The provided reproduction is a minimal reproducible example of the bug.

[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• vitejs-vite-px4o6w (Open reproduction)