feat: Add method to configure loaders rules

index.js

@@ -1100,6 +1100,32 @@ class Encore {
         return this;
     }
 
+    /**
+     * Configure Webpack loaders rules (`module.rules`).
+     * This is a low-level function, be careful when using it.
+     *
+     * https://webpack.js.org/concepts/loaders/#configuration
+     *
+     * For example, if you are using Vue and ESLint loader,
+     * this is how you can configure ESLint to lint Vue files:
+     *
+     *     Encore
+     *         .enableEslintLoader()
+     *         .enableVueLoader()
+     *         .configureLoaderRule('eslint', (loaderRule) => {
+     *              loaderRule.test = /\.(jsx?|vue)/;
+     *         });
+     *
+     * @param {string} name
+     * @param {function} callback
+     * @return {Encore}
+     */
+    configureLoaderRule(name, callback) {
+        webpackConfig.configureLoaderRule(name, callback);
+
+        return this;
+    }
+
     /**
      * If enabled, the output directory is emptied between each build (to remove old files).
      *

lib/WebpackConfig.js

@@ -100,6 +100,19 @@ class WebpackConfig {
         this.eslintLoaderOptionsCallback = () => {};
         this.tsConfigurationCallback = () => {};
         this.handlebarsConfigurationCallback = () => {};
+        this.loaderConfigurationCallbacks = {
+            javascript: () => {},
+            css: () => {},
+            images: () => {},
+            fonts: () => {},
+            sass: () => {},
+            less: () => {},
+            stylus: () => {},
+            vue: () => {},
+            eslint: () => {},
+            typescript: () => {},
+            handlebars: () => {},
+        };
 
         // Plugins options
         this.cleanWebpackPluginPaths = ['**/*'];
@@ -716,6 +729,31 @@ class WebpackConfig {
         });
     }
 
+    configureLoaderRule(name, callback) {
+        logger.warning('Be careful when using Encore.configureLoaderRule(), this is a low-level method that can potentially break Encore and Webpack when not used carefully.');
+
+        // Key: alias, Value: existing loader in `this.loaderConfigurationCallbacks`
+        const aliases = {
+            js: 'javascript',
+            ts: 'typescript',
+            scss: 'sass',
+        };
+
+        if (name in aliases) {
+            name = aliases[name];
+        }
+
+        if (!(name in this.loaderConfigurationCallbacks)) {
+            throw new Error(`Loader "${name}" is not configurable. Valid loaders are "${Object.keys(this.loaderConfigurationCallbacks).join('", "')}" and the aliases "${Object.keys(aliases).join('", "')}".`);
+        }
+
+        if (typeof callback !== 'function') {
+            throw new Error('Argument 2 to configureLoaderRule() must be a callback function.');
+        }
+
+        this.loaderConfigurationCallbacks[name] = callback;
+    }
+
     useDevServer() {
         return this.runtimeConfig.useDevServer;
     }

lib/config-generator.js

@@ -221,14 +221,18 @@ class ConfigGenerator {
     }
 
     buildRulesConfig() {
+        const applyRuleConfigurationCallback = (name, defaultRules) => {
+            return applyOptionsCallback(this.webpackConfig.loaderConfigurationCallbacks[name], defaultRules);
+        };
+
         let rules = [
-            {
+            applyRuleConfigurationCallback('javascript', {
                 // match .js and .jsx
                 test: /\.jsx?$/,
                 exclude: this.webpackConfig.babelOptions.exclude,
                 use: babelLoaderUtil.getLoaders(this.webpackConfig)
-            },
-            {
+            }),
+            applyRuleConfigurationCallback('css', {
                 test: /\.css$/,
                 oneOf: [
                     {
@@ -245,7 +249,7 @@ class ConfigGenerator {
                         )
                     }
                 ]
-            }
+            })
         ];
 
         if (this.webpackConfig.useImagesLoader) {
@@ -269,11 +273,11 @@ class ConfigGenerator {
                 Object.assign(loaderOptions, this.webpackConfig.urlLoaderOptions.images);
             }
 
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('images', {
                 test: /\.(png|jpg|jpeg|gif|ico|svg|webp)$/,
                 loader: loaderName,
                 options: loaderOptions
-            });
+            }));
         }
 
         if (this.webpackConfig.useFontsLoader) {
@@ -297,15 +301,15 @@ class ConfigGenerator {
                 Object.assign(loaderOptions, this.webpackConfig.urlLoaderOptions.fonts);
             }
 
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('fonts', {
                 test: /\.(woff|woff2|ttf|eot|otf)$/,
                 loader: loaderName,
                 options: loaderOptions
-            });
+            }));
         }
 
         if (this.webpackConfig.useSassLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('sass', {
                 test: /\.s[ac]ss$/,
                 oneOf: [
                     {
@@ -316,11 +320,11 @@ class ConfigGenerator {
                         use: cssExtractLoaderUtil.prependLoaders(this.webpackConfig, sassLoaderUtil.getLoaders(this.webpackConfig))
                     }
                 ]
-            });
+            }));
         }
 
         if (this.webpackConfig.useLessLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('less', {
                 test: /\.less/,
                 oneOf: [
                     {
@@ -331,11 +335,11 @@ class ConfigGenerator {
                         use: cssExtractLoaderUtil.prependLoaders(this.webpackConfig, lessLoaderUtil.getLoaders(this.webpackConfig))
                     }
                 ]
-            });
+            }));
         }
 
         if (this.webpackConfig.useStylusLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('stylus', {
                 test: /\.styl/,
                 oneOf: [
                     {
@@ -346,39 +350,39 @@ class ConfigGenerator {
                         use: cssExtractLoaderUtil.prependLoaders(this.webpackConfig, stylusLoaderUtil.getLoaders(this.webpackConfig))
                     }
                 ]
-            });
+            }));
         }
 
         if (this.webpackConfig.useVueLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('vue', {
                 test: /\.vue$/,
                 use: vueLoaderUtil.getLoaders(this.webpackConfig)
-            });
+            }));
         }
 
         if (this.webpackConfig.useEslintLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('eslint', {
                 test: /\.jsx?$/,
                 loader: 'eslint-loader',
                 exclude: /node_modules/,
                 enforce: 'pre',
                 options: eslintLoaderUtil.getOptions(this.webpackConfig)
-            });
+            }));
         }
 
         if (this.webpackConfig.useTypeScriptLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('typescript', {
                 test: /\.tsx?$/,
                 exclude: /node_modules/,
                 use: tsLoaderUtil.getLoaders(this.webpackConfig)
-            });
+            }));
         }
 
         if (this.webpackConfig.useHandlebarsLoader) {
-            rules.push({
+            rules.push(applyRuleConfigurationCallback('handlebars', {
                 test: /\.(handlebars|hbs)$/,
                 use: handlebarsLoaderUtil.getLoaders(this.webpackConfig)
-            });
+            }));
         }
 
         this.webpackConfig.loaders.forEach((loader) => {

test/WebpackConfig.js

@@ -1144,4 +1144,36 @@ describe('WebpackConfig object', () => {
             }).to.throw('Argument 1 to configureWatchOptions() must be a callback function.');
         });
     });
+
+    describe('configureLoaderRule()', () => {
+        it('works properly', () => {
+            const config = createConfig();
+            const callback = (loader) => {};
+
+            expect(config.loaderConfigurationCallbacks['eslint']).to.not.equal(callback);
+
+            config.configureLoaderRule('eslint', callback);
+            expect(config.loaderConfigurationCallbacks['eslint']).to.equal(callback);
+        });
+
+        it('Call method with a not supported loader', () => {
+            const config = createConfig();
+
+            expect(() => {
+                config.configureLoaderRule('reason');
+            }).to.throw('Loader "reason" is not configurable. Valid loaders are "javascript", "css", "images", "fonts", "sass", "less", "stylus", "vue", "eslint", "typescript", "handlebars" and the aliases "js", "ts", "scss".');
+        });
+
+        it('Call method with not a valid callback', () => {
+            const config = createConfig();
+
+            expect(() => {
+                config.configureLoaderRule('eslint');
+            }).to.throw('Argument 2 to configureLoaderRule() must be a callback function.');
+
+            expect(() => {
+                config.configureLoaderRule('eslint', {});
+            }).to.throw('Argument 2 to configureLoaderRule() must be a callback function.');
+        });
+    });
 });