base configuration option can break vite's raw fs handler in devserver

[JDP]

What version of astro are you using?

2.7.1

Are you using an SSR adapter? If so, which one?

None

What package manager are you using?

npm

What operating system are you using?

Linux

What browser are you using?

Chrome

Describe the Bug

If you set the base config option to a part of a folder name that exists in the root, vite will not be able to load any files under that path.

This code right here:
https://github.com/withastro/astro/blob/main/packages/astro/src/vite-plugin-astro-server/plugin.ts#L46-L52

Places the 'base' middleware before the raw fs handler, and in the base middleware there's this bit of code:
https://github.com/withastro/astro/blob/main/packages/astro/src/vite-plugin-astro-server/base.ts#L25-L28

If you create an astro.config with the base option set to say, 'src' (like the linked example) where all your files are located, this will cause the urls to any files loaded on the client to get converted from /src/my-file.ts to /my-file.ts, which will result in a 404 as the file is not at that path.

This also happens if you set trailingSlashes to never, in that case it breaks any file with the same prefix as your base path (so in my case, i had a base path of '/no', which turns all '/node_modules' to '/de_modules')

My workaround for now is to move the mw around in the devserver with a vite plugin, so that the base middleware is placed just before astroDevHandler, and moving the viteServePublicMiddleware to run after the base middleware as those files should have their base path stripped.

I'm not sure what the cleanest real solution would be, there are some quick fixes like not modifying the URL if there's an "astro" querystring parameter, but '@vite/client' etc scripts does not include that, so there could still be issues.

What's the expected result?

The raw fs handler in vite should be able to serve any local files in the project regardless of the base configuration option value.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-hajh6e

Participation

• I am willing to submit a pull request for this issue.

[Bjorn Lu]

I took a stab fixing this today at https://github.com/withastro/astro/tree/improve-base-handling. However that exploded in scope as I realized Astro doesn't pass the base to Vite, and it changes the base handling order (as you mentioned). Both can possibly break Vite plugin compatibility as Vite plugins can't reliably detect the base.

I think overall it will be a breaking change, so something we could fix later. We can probably scope down the issue first by properly preprending the base to the URLs, e.g. /src/my-file.ts should be /my-base/src/file.ts, which is what Vite does too. I'll try to tackle this later.