Describe the bug

When an imported scss file has variable url($foo) links, they get badly rewritten:

scss-import-test/index.scss:

$default-image-1: "/default.png";
$default-image-2: "./default.png";
$default-image-3: "default.png";

body {
  background-image: url($default-image-1);
  background-image: url($default-image-2);
  background-image: url($default-image-3);
  background-image: url("/default.png");
  background-image: url("./default.png");
  background-image: url("default.png");
}

Gets rewritten as (notice the invalid css):

body {
  background-image: url(node_modules/scss-import-test/"/default.png"); // NOK
  background-image: url(node_modules/scss-import-test/"./default.png"); // NOK
  background-image: url(node_modules/scss-import-test/"default.png"); // NOK
  background-image: url("/default.png");
  background-image: url("/node_modules/scss-import-test/default.png"); // OK
  background-image: url("/node_modules/scss-import-test/default.png"); // OK
}

Note that when imported through another (intermediate) scss file, the output is different:
scss-import-test/nested.scss:

@import './index.scss'

Results into (valid css, but the paths aren't rewritten):

body {
  background-image: url("/default.png");
  background-image: url("./default.png");
  background-image: url("default.png");
  background-image: url("/default.png");
  background-image: url("./default.png");
  background-image: url("default.png");
}

I believe this erratic behavior is caused by rebaseUrls/rewriteCssUrls being executed on (raw SCSS) content from the first import from src (and only the first, further imports will get processed by vite-url-rewrite postcss plugin, on CSS ast, with variable interpolated), can probably submit a PR if agreed.

Reproduction

https://stackblitz.com/edit/vite-dgawmt?file=index.scss

System Info

Stackbliz doesn't run envinfo.
vite@2.6.9

Used Package Manager

npm

Logs

No response

Validations

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