Fix non file scheme in SASS

Fixes #10019

Author: devongovett

packages/core/integration-tests/test/sass.js

@@ -399,4 +399,30 @@ describe('sass', function () {
       inputFS: overlayFS,
     });
   });
+
+  it('should support npm scheme', async function () {
+    const dir = path.join(__dirname, 'sass-extensions');
+    overlayFS.mkdirp(dir);
+
+    await fsFixture(overlayFS, dir)`
+      index.js:
+        import './main.scss';
+
+      main.scss:
+        @use 'npm:test' as test;
+
+      node_modules/test/package.json:
+        { "name": "test" }
+
+      node_modules/test/_index.scss:
+        @use 'other';
+
+      node_modules/test/_other.scss:
+        .foo { color: red }
+      `;
+
+    await bundle(path.join(dir, '/index.js'), {
+      inputFS: overlayFS,
+    });
+  });
 });

packages/transformers/sass/src/modern.js

@@ -98,7 +98,7 @@ function resolvePathImporter({
       let containingPath = containingUrl
         ? fileURLToPath(containingUrl)
         : asset.filePath;
-      if (!containingUrl) {
+      if (!containingUrl && url.startsWith('file:')) {
         // If containingUrl is not provided, then url should be an absolute file:/// URL.
         let filePath = fileURLToPath(url);
         url = path.relative(path.dirname(containingPath), filePath);