Support webpack v4 new plugin API

Author: NMFR

README.md

@@ -17,6 +17,8 @@ Using npm:
 $ npm install --save-dev optimize-css-assets-webpack-plugin
 ```
 
+> :warning: For webpack v3 or below please use `optimize-css-assets-webpack-plugin@3.2.0`. The `optimize-css-assets-webpack-plugin@4.0.0` version and above supports webpack v4.
+
 ## Configuration:
 
 The plugin can receive the following options (all of them are optional):

index.js

@@ -5,9 +5,9 @@
   "description": "A Webpack plugin to optimize \\ minimize CSS assets.",
   "dependencies": {
     "cssnano": "^3.4.0",
-    "last-call-webpack-plugin": "^2.1.2"
+    "last-call-webpack-plugin": "^3.0.0"
   },
-  "main": "index.js",
+  "main": "src/index.js",
   "homepage": "http://github.com/NMFR/optimize-css-assets-webpack-plugin",
   "repository": {
     "type": "git",

package-lock.json

@@ -0,0 +1,69 @@
+const LastCallWebpackPlugin = require('last-call-webpack-plugin');
+
+class OptimizeCssAssetsWebpackPlugin extends LastCallWebpackPlugin {
+  constructor(options) {
+    super({
+      assetProcessors: [
+        {
+          phase: LastCallWebpackPlugin.PHASES.OPTIMIZE_CHUNK_ASSETS,
+          regExp: (options && options.assetNameRegExp) || /\.css$/g,
+          processor: (assetName, asset, assets) =>
+            this.processCss(assetName, asset, assets),
+        }
+      ],
+      canPrint: options && options.canPrint,
+    });
+
+    this.options.assetNameRegExp = !options || !options.assetNameRegExp ?
+      /\.css$/g :
+      options.assetNameRegExp;
+    this.options.cssProcessor = !options || !options.cssProcessor ?
+        require('cssnano') :
+        options.cssProcessor;
+    this.options.cssProcessorOptions = !options || options.cssProcessorOptions === undefined ?
+      {} :
+      options.cssProcessorOptions;
+  }
+
+  buildPluginDescriptor() {
+    return { name: 'OptimizeCssAssetsWebpackPlugin' };
+  }
+
+  processCss(assetName, asset, assets) {
+    const css = asset.source();
+    const processOptions = Object.assign(
+      { from: assetName, to: assetName },
+      this.options.cssProcessorOptions || {}
+    );
+
+    if (processOptions.map && !processOptions.map.prev) {
+      try {
+        const mapJson = assets.getAsset(assetName + '.map');
+        if (mapJson) {
+          const map = JSON.parse(mapJson);
+          if (
+            map &&
+            (
+              (map.sources && map.sources.length > 0) ||
+              (map.mappings && map.mappings.length > 0)
+            )
+          ) {
+            processOptions.map = Object.assign({ prev: mapJson }, processOptions.map);
+          }
+        }
+      } catch (err) {
+        console.warn('OptimizeCssAssetsPlugin.processCss() Error getting previous source map', err);
+      }
+    }
+    return this.options
+      .cssProcessor.process(css, processOptions)
+      .then(r => {
+        if (processOptions.map && r.map && r.map.toString) {
+          assets.setAsset(assetName + '.map', r.map.toString());
+        }
+        return r.css;
+      });
+  }
+}
+
+module.exports = OptimizeCssAssetsWebpackPlugin;