Vite: Don't rebase urls that appear to be aliases (#16078)

Closes #16039

This PR changes our URL rebasing logic used with Vite so that it does
not rebase URLs that look like common alias paths (e.g. urls starting in
`~`, `@` or `#`, etc.). Unfortunately this is only an approximation and
you can configure an alias for a path that starts with a regular
alphabetical character (e.g. `foo` => `./my/foo`) so this isn't a
perfect fix, however in practice most aliases will be prefixed with a
symbol to make it clear that it's an alias anyways.

One alternative we have considered is to only rebase URLs that we know
are relative (so they need to start with a `.`). This, however, will
break common CSS use cases where urls are loaded like this:

```css
background: image-set(
  url('image1.jpg') 1x,
  url('image2.jpg') 2x
);
``` 

So making this change felt like we only trade one GitHub issue for
another one.

In a more ideal scenario we try to resolve the URL with the Vite
resolver (we have to run the resolver and can't rely on the `resolve`
setting alone due to packages like
[`vite-tsconfig-paths`](https://www.npmjs.com/package/vite-tsconfig-paths)),
however even then we can have relative paths being resolvable to
different files based on wether they were rebased or not (e.g. when an
image with the same filename exists in two different paths).

So ultimately we settled on extending the already existing blocklist
(which we have taken from the Vite implementation) for now.

## Test plan

- Added unit test and it was tested with the Vite playground.

---------

Co-authored-by: Robin Malfait <malfait.robin@gmail.com>

Author: philipp-spiess

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Refactor gradient implementation to work around [prettier/prettier#17058](https://github.com/prettier/prettier/issues/17058) ([#16072](https://github.com/tailwindlabs/tailwindcss/pull/16072))
 - Vite: Ensure hot-reloading works with SolidStart setups ([#16052](https://github.com/tailwindlabs/tailwindcss/pull/16052))
 - Vite: Fix a crash when starting the development server in SolidStart setups ([#16052](https://github.com/tailwindlabs/tailwindcss/pull/16052))
+- Vite: Don't rebase urls that appear to be aliases ([#16078](https://github.com/tailwindlabs/tailwindcss/pull/16078))
 - Prevent camelCasing CSS custom properties added by JavaScript plugins ([#16103](https://github.com/tailwindlabs/tailwindcss/pull/16103))
 - Do not emit `@keyframes` in `@theme reference` ([#16120](https://github.com/tailwindlabs/tailwindcss/pull/16120))
 

packages/@tailwindcss-node/src/urls.test.ts

@@ -24,6 +24,20 @@ test('URLs can be rewritten', async () => {
         background: url('/image.jpg');
         background: url("/image.jpg");
 
+        /* Potentially Vite-aliased URLs: ignored */
+        background: url(~/image.jpg);
+        background: url(~/foo/image.jpg);
+        background: url('~/image.jpg');
+        background: url("~/image.jpg");
+        background: url(#/image.jpg);
+        background: url(#/foo/image.jpg);
+        background: url('#/image.jpg');
+        background: url("#/image.jpg");
+        background: url(@/image.jpg);
+        background: url(@/foo/image.jpg);
+        background: url('@/image.jpg');
+        background: url("@/image.jpg");
+
         /* External URL: ignored */
         background: url(http://example.com/image.jpg);
         background: url('http://example.com/image.jpg');
@@ -109,6 +123,18 @@ test('URLs can be rewritten', async () => {
       background: url(/foo/image.jpg);
       background: url('/image.jpg');
       background: url("/image.jpg");
+      background: url(~/image.jpg);
+      background: url(~/foo/image.jpg);
+      background: url('~/image.jpg');
+      background: url("~/image.jpg");
+      background: url(#/image.jpg);
+      background: url(#/foo/image.jpg);
+      background: url('#/image.jpg');
+      background: url("#/image.jpg");
+      background: url(@/image.jpg);
+      background: url(@/foo/image.jpg);
+      background: url('@/image.jpg');
+      background: url("@/image.jpg");
       background: url(http://example.com/image.jpg);
       background: url('http://example.com/image.jpg');
       background: url("http://example.com/image.jpg");

packages/@tailwindcss-node/src/urls.ts

@@ -149,9 +149,12 @@ async function doUrlReplace(
   return `${funcName}(${wrap}${newUrl}${wrap})`
 }
 
-function skipUrlReplacer(rawUrl: string) {
+function skipUrlReplacer(rawUrl: string, aliases?: string[]) {
   return (
-    isExternalUrl(rawUrl) || isDataUrl(rawUrl) || rawUrl[0] === '#' || functionCallRE.test(rawUrl)
+    isExternalUrl(rawUrl) ||
+    isDataUrl(rawUrl) ||
+    !rawUrl[0].match(/[\.a-zA-Z0-9_]/) ||
+    functionCallRE.test(rawUrl)
   )
 }