add support for webpack 4

We currently already have support for webpack4, so I just needed to
add some tests.

package.json

@@ -12,8 +12,9 @@
     "test:webpack1": "npm install -q webpack@1.x && npm run test:clean && webpack --config test/webpack1.config.js",
     "test:webpack2": "npm install -q webpack@2.x && npm run test:clean && webpack --config test/webpack2.config.js",
     "test:webpack3": "npm install -q webpack@3.x && npm run test:clean && webpack --config test/webpack2.config.js",
+    "test:webpack4": "npm install -q webpack@4.x webpack-cli && npm run test:clean && webpack --config test/webpack4.config.js",
     "test:clean": "rm -rf test/public/assets",
-    "test": "npm run test:webpack1 && npm run test:webpack2 && npm run test:webpack3"
+    "test": "npm run test:webpack1 && npm run test:webpack2 && npm run test:webpack3 && npm run test:webpack4"
   },
   "dependencies": {
     "imagemin": "^5.2.2",
@@ -24,9 +25,10 @@
     "imagemin-svgo": "^6.0.0",
     "imagemin-webp": "^4.0.0",
     "loader-utils": "^1.1.0",
-    "object-assign": "^4.1.1"
+    "object-assign": "^4.1.1",
+    "webpack-cli": "^2.1.3"
   },
   "devDependencies": {
-    "file-loader": "^0.10.1"
+    "file-loader": "^1.1.11"
   }
 }

test/webpack4.config.js

@@ -0,0 +1,77 @@
+'use strict';
+var path = require('path');
+var webpack = require('webpack');
+
+var assetsPath = path.join(__dirname, 'public/assets');
+
+var loaderOptions = {
+  mozjpeg: {
+    quality: 65
+  },
+  pngquant:{
+    quality: "65-90",
+    speed: 4
+  },
+  svgo:{
+    plugins: [
+      {
+        removeViewBox: false
+      },
+      {
+        removeEmptyAttrs: false
+      }
+    ]
+  },
+  gifsicle: {
+    optimizationLevel: 7,
+    interlaced: false
+  },
+  optipng: {
+    optimizationLevel: 7,
+    interlaced: false
+  },
+  webp: {
+    quality: 75
+  }
+}
+
+var fileLoaderOptions = {
+  hash: 'sha512',
+  digest: 'hex',
+  name: '[hash].[ext]'
+}
+
+module.exports = [
+  {
+    mode: 'production',
+    entry: './test/app.js',
+    output: {
+      path: assetsPath,
+      filename: 'app.[hash].js'
+    },
+    module: {
+      rules: [{
+        test: /.*\.(gif|png|jpe?g|svg|webp)$/i,
+        use: [
+          {
+            loader: 'file-loader',
+            options: fileLoaderOptions
+          },
+          {
+            loader: require.resolve('../'),
+            options: loaderOptions
+          }
+        ]
+      }, {
+        test: /\.bmp$/i,
+        use: [
+          {
+            loader: 'file-loader',
+            options: fileLoaderOptions
+          },
+          require.resolve('../') // loaderUtils.getOptions() returns null for this one
+        ]
+      }]
+    }
+  }
+];