3.1.0 regression: html attrs without quotes are broken

[mustafa0x]

Describe the bug

Removing the quotes around src's value (ie <script type="module" src=/main.js></script>) causes vite to request main.jss.

See the reproduction link (it's the exact vite.new template, except I removed the quotes around /main.js). Add back the quotes and it will work. This is a regression (works fine in 3.0.9).

Reproduction

https://stackblitz.com/edit/vitejs-vite-blze7m?file=index.html

System Info

vite

Used Package Manager

pnpm

Logs

No response

Validations

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