fix: resolution for file scheme

src/webpackImporter.js

@@ -70,41 +70,59 @@ function webpackImporter(loaderContext, includePaths) {
     mainFiles: [],
     modules: [],
   });
+  // TODO implement the `restrictions` option for `enhanced-resolve` and avoid resolution `js` files from the `mainFields`
+  // TODO avoid resolsing `_index`, `index` and files without extensions
+  // TODO avoid resolving with multiple extensions - `file.sass.sass`/`file.sass.scss`/`file.sass.css`
   const webpackResolve = loaderContext.getResolve({
     mainFields: ['sass', 'style', 'main', '...'],
     mainFiles: ['_index', 'index', '...'],
     extensions: ['.sass', '.scss', '.css'],
   });
 
-  return (url, prev, done) => {
-    // The order of import precedence is as follows:
-    //
-    // 1. Filesystem imports relative to the base file.
-    // 2. Custom importer imports.
-    // 3. Filesystem imports relative to the working directory.
-    // 4. Filesystem imports relative to an `includePaths` path.
-    // 5. Filesystem imports relative to a `SASS_PATH` path.
-    //
-    // Because `sass`/`node-sass` run custom importers after `3`, `4` and `5` points, we need to emulate this behavior to avoid wrong resolution.
-    const sassPossibleRequests = getPossibleRequests(url);
-    const webpackPossibleRequests = getPossibleRequests(url, true);
-    const resolutionMap = []
-      .concat(
+  return (originalUrl, prev, done) => {
+    let url = originalUrl;
+
+    const isFileScheme = originalUrl.startsWith('file:');
+
+    if (isFileScheme) {
+      // eslint-disable-next-line no-param-reassign
+      url = originalUrl.slice(5);
+    }
+
+    let resolutionMap = [];
+
+    if (includePaths.length > 0 && !isFileScheme) {
+      // The order of import precedence is as follows:
+      //
+      // 1. Filesystem imports relative to the base file.
+      // 2. Custom importer imports.
+      // 3. Filesystem imports relative to the working directory.
+      // 4. Filesystem imports relative to an `includePaths` path.
+      // 5. Filesystem imports relative to a `SASS_PATH` path.
+      //
+      // Because `sass`/`node-sass` run custom importers before `3`, `4` and `5` points, we need to emulate this behavior to avoid wrong resolution.
+      const sassPossibleRequests = getPossibleRequests(url);
+
+      resolutionMap = resolutionMap.concat(
         includePaths.map((context) => ({
           resolve: sassResolve,
           context,
           possibleRequests: sassPossibleRequests,
         }))
-      )
-      .concat({
-        resolve: webpackResolve,
-        context: dirContextFrom(prev),
-        possibleRequests: webpackPossibleRequests,
-      });
+      );
+    }
+
+    const webpackPossibleRequests = getPossibleRequests(url, true);
+
+    resolutionMap = resolutionMap.concat({
+      resolve: webpackResolve,
+      context: isFileScheme ? '/' : dirContextFrom(prev),
+      possibleRequests: webpackPossibleRequests,
+    });
 
     startResolving(resolutionMap)
       // Catch all resolving errors, return the original file and pass responsibility back to other custom importers
-      .catch(() => ({ file: url }))
+      .catch(() => ({ file: originalUrl }))
       .then(done);
   };
 }

test/helpers/getCodeFromSass.js

@@ -252,6 +252,9 @@ function getCodeFromSass(testId, options) {
     testFolder,
     'node_modules/package-with-js-and-css-main-files/index'
   );
+  const pathToLanguage = isSass
+    ? path.resolve(testFolder, 'sass/language.sass')
+    : path.resolve(testFolder, 'scss/language.scss');
 
   // Pseudo importer for tests
   function testImporter(url) {
@@ -710,6 +713,7 @@ function getCodeFromSass(testId, options) {
           /^~package-with-js-and-css-main-files/,
           pathToPackageWithJsAndCssMainFiles
         )
+        .replace(/^file:language/, pathToLanguage)
         .replace(/^~/, testNodeModules);
     }
 

test/loader.test.js

@@ -721,6 +721,30 @@ describe('loader', () => {
         expect(getErrors(stats)).toMatchSnapshot('errors');
       });
 
+      // TODO need fix on webpack@5 side
+      it.skip(`should support resolving using the "file" schema (${implementationName}) (${syntax})`, async () => {
+        const testId = getTestId('import-file-scheme', syntax);
+        const options = {
+          implementation: getImplementationByName(implementationName),
+        };
+        const compiler = getCompiler(testId, {
+          loader: { options },
+          resolve: {
+            alias: {
+              '/language': path.resolve('./test', syntax, `language.${syntax}`),
+            },
+          },
+        });
+        const stats = await compile(compiler);
+        const codeFromBundle = getCodeFromBundle(stats, compiler);
+        const codeFromSass = getCodeFromSass(testId, options);
+
+        expect(codeFromBundle.css).toBe(codeFromSass.css);
+        expect(codeFromBundle.css).toMatchSnapshot('css');
+        expect(getWarnings(stats)).toMatchSnapshot('warnings');
+        expect(getErrors(stats)).toMatchSnapshot('errors');
+      });
+
       if (implementation === dartSass) {
         it(`should output an understandable error with a problem in "@use" (${implementationName}) (${syntax})`, async () => {
           const testId = getTestId('error-use', syntax);

test/sass/import-file-scheme.sass

@@ -0,0 +1 @@
+@import 'file:language'

test/scss/import-file-scheme.scss

@@ -0,0 +1 @@
+@import 'file:language';