feat: Add the ability to pass in a custom resolver

lib/normalizeOptions.js

@@ -85,7 +85,16 @@ function normalizeOptions(loaderContext, content, webpackImporter) {
   options.importer = options.importer
     ? proxyCustomImporters(options.importer, resourcePath)
     : [];
-  options.importer.push(webpackImporter);
+
+  if (options.resolver === false) {
+    // disable webpack resolved in favor built-in node-sass/sass resolver
+  } else if (typeof options.resolver === 'function') {
+    options.importer = options.importer.concat(
+      proxyCustomImporters(options.resolver, resourcePath)
+    );
+  } else {
+    options.importer.push(webpackImporter);
+  }
 
   // `node-sass` uses `includePaths` to resolve `@import` paths. Append the currently processed file.
   options.includePaths = options.includePaths || [];

test/index.test.js

@@ -13,6 +13,7 @@ const dartSass = require('sass');
 const mockRequire = require('mock-require');
 
 const customImporter = require('./tools/customImporter.js');
+const customResolver = require('./tools/customResolver.js');
 const customFunctions = require('./tools/customFunctions.js');
 
 const pathToSassLoader = require.resolve('../lib/loader.js');
@@ -185,6 +186,19 @@ implementations.forEach((implementation) => {
               importer: customImporter,
             }));
         });
+        describe('custom resolver', () => {
+          it('should use custom resolver', () =>
+            execTest('custom-resolver', {
+              resolver: customResolver,
+            }));
+        });
+        describe('no resolver', () => {
+          it('should use custom resolver', () =>
+            execTest('no-resolver', {
+              resolver: false,
+              includePaths: [path.join(__dirname, 'node_modules', 'scss')],
+            }));
+        });
         describe('custom functions', () => {
           it('should expose custom functions', () =>
             execTest('custom-functions', {

test/sass/custom-resolver.sass

@@ -0,0 +1 @@
+@import import-with-custom-resolver

test/sass/no-resolver.sass

@@ -0,0 +1 @@
+@import unresolvable

test/scss/custom-resolver.scss

@@ -0,0 +1 @@
+@import 'import-with-custom-resolver';

test/scss/no-resolver.scss

@@ -0,0 +1 @@
+@import 'unresolvable';

test/tools/createSpec.js

@@ -8,6 +8,7 @@ const dartSass = require('sass');
 const nodeSass = require('node-sass');
 
 const customImporter = require('./customImporter.js');
+const customResolver = require('./customResolver.js');
 const customFunctions = require('./customFunctions.js');
 
 const implementations = [nodeSass, dartSass];
@@ -22,6 +23,10 @@ function createSpec(ext) {
     basePath,
     path.resolve(testFolder, '..', 'node_modules', 'bootstrap-sass')
   );
+  const pathToUnresolvable = path.relative(
+    basePath,
+    path.resolve(testFolder, 'node_modules', 'scss', 'unresolvable.scss')
+  );
   const pathToScopedNpmPkg = path.relative(
     basePath,
     path.resolve(testFolder, 'node_modules', '@org', 'pkg', './index.scss')
@@ -73,6 +78,9 @@ function createSpec(ext) {
           if (url === 'import-with-custom-logic') {
             return customImporter.returnValue;
           }
+          if (url === 'import-with-custom-resolver') {
+            return customResolver.returnValue;
+          }
           // Do not transform css imports
           if (/\.css$/.test(url) === false) {
             // eslint-disable-next-line no-param-reassign
@@ -83,6 +91,7 @@ function createSpec(ext) {
               .replace(/^~@org\/pkg/, pathToScopedNpmPkg)
               .replace(/^~module/, pathToModule)
               .replace(/^~another/, pathToAnother)
+              .replace(/^unresolvable/, pathToUnresolvable)
               .replace(/^~/, testNodeModules)
               .replace(/^path-to-alias/, pathToFooAlias);
           }

test/tools/customResolver.js

@@ -0,0 +1,18 @@
+'use strict';
+
+require('should');
+
+function customResolver(path, prev) {
+  path.should.equal('import-with-custom-resolver');
+  prev.should.match(/(sass|scss)[/\\]custom-resolver\.(scss|sass)/);
+
+  this.should.have.property('options'); // eslint-disable-line no-invalid-this
+
+  return customResolver.returnValue;
+}
+
+customResolver.returnValue = {
+  contents: '.custom-resolver {}',
+};
+
+module.exports = customResolver;