devserver serves source files instead of index.html since v7.0.5

[schiller-manuel]

Describe the bug

Since version 7.0.5, vite devserver serves source files instead of index.html when the url path matches the basename of a file inside the project.

originally reported here: TanStack/router#5052

Reproduction

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

Steps to reproduce

1. go to https://stackblitz.com/edit/vitejs-vite-sfcqpwnb
2. click on "open preview in new tab"
3. click on "click me" that opens the dev server at /test
4. you will see the contents of test.js served from /test

here is the same project with vite 7.0.4 that works as expected:
https://stackblitz.com/edit/vitejs-vite-tgbe56vv

System Info

starts happening since vite 7.0.5

Used Package Manager

npm

Logs

No response

Validations

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• 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 vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[hi-ogawa]

The change is due to #20376. Technically the behavior became more consistent since curl http://localhost:5173/test has been always serving test.js. I'm not sure if there's a workaround on user land. If this breakage is worse than original bug #17340, then maybe reverting might be an option. @sapphi-red What do you think?

[sapphi-red]

I think we need to add back this part and add a bit more code, otherwise I guess /test will serve /test.js when accessing the second time (I could be misremembering).
https://github.com/vitejs/vite/pull/20376/files#diff-5ac5675edd621a639999ba602b8795d985ca4bc7c9098473e6692d04e34291d9L273-L277
The changes I guess we need are:

• add Vary: Accept
• make cachedTransformMiddleware to handle Accept: text/html
• (optional) I guess we should use Sec-Fetch-Dest: document/Sec-Fetch-Dest: frame/Sec-Fetch-Dest: iframe instead of Accept: text/html

[pi0]

Facing the same limit with the Nitro Vite plugin + SSR rendering, conflicting with root files.

Added a temporary workaround: nitrojs/nitro@f7d32d9