This PR fixes an issue where resolving of certain CSS or JS files
results in the wrong paths. The issue happens if you have a setup where
a relative file path _also_ exists in the parent folder:
```css
/* src/foo.css */
.foo-in-root {}
/* src/theme/a.css */
@import "./foo.css"; /* This resolved to the file above, instead of the file below */
/* src/theme/foo.css */
.foo-in-theme {}
```
This happened because we resolved relative to a `base` folder, but Vite
expects an `importer` instead. The difference is subtle, but they expect
a file. On that file they use `let base = path.dirname(importer)` to get
a base path out themselves.
This in turn means that if you pass in a folder, you get this:
```js
path.dirname('/path/to/my-project') // /path/to
```
If we gave it a proper file, then we get the proper base path
```js
path.dirname('/path/to/my-project/index.css') // /path/to/my-project
```
I'm actually surprised that this didn't cause issues earlier... but it
did result in error since we recently started resolving files using
Vite's `aliasOnly: true` feature such taht Vite aliases work as well.
With this change, we now make sure that:
1. We use a proper `importer` instead of the `base` path
2. We refactor the resolving logic such that we try with `aliasOnly:
true` first, then `aliasOnly: false`
We also still ensure that in the CSS resolver we expect a `.css` file,
and in the JS resolver we _don't_ expect a `.css` file (which can happen
if a `"browser": "./dist/index.css"` field in package.json points to a
CSS file, daisyUI does this for example).
Fixes: #19956
## Test plan
1. Added additional (failing) integration tests to reproduce the linked
issue
2. Existing integration tests pass
While the build still worked, the linked issue resulted in a much bigger
file size because the wrong .css files were included. With this fix, the
number is correct again:
<img width="1234" height="1037" alt="image"
src="https://github.com/user-attachments/assets/fdff803c-0db2-4066-92fa-064c2816b35c"
/>
Since this is touching code related to previous PRs, I wanted to
manually make sure that these still work as expected:
- https://github.com/tailwindlabs/tailwindcss/issues/19950: This one is
about daisyUI and the `.css` file referenced in the package.json's
`"browser"` field: <img width="782" height="1229" alt="image"
src="https://github.com/user-attachments/assets/fb7b9d3b-527b-414b-94b0-2be7e96056f1"
/>
- https://github.com/tailwindlabs/tailwindcss/issues/19946: This one is
about the Vite alias being just a single `@` causing issues with
`@plugin "@tailwindcss/typography";` for example: <img width="1694"
height="1856" alt="image"
src="https://github.com/user-attachments/assets/d1935ecf-e80a-4945-a69a-ec3c5223efab"
/>
[ci-all]
5a799900d4