Feature/postcss option as function

README.md

@@ -70,6 +70,43 @@ module.exports = {
 }
 ```
 
+## Plugins Function
+
+If you need to link any of the postcss plugins to the webpack context, you can
+define a function that returns your plugins. The function is executed with the
+same context provided to postcss-loader, allowing access to webpack loader API
+
+```js
+var cssimport = require('postcss-import');
+var autoprefixer = require('autoprefixer-core');
+
+module.exports = {
+    module: {
+        loaders: [
+            {
+                test:   /\.css$/,
+                loader: "style-loader!css-loader!postcss-loader"
+            }
+        ]
+    },
+    postcss: function () {
+        // The context of this function is the same provided to postcss-loader
+        // see: http://webpack.github.io/docs/loaders.html
+
+        return [
+            cssimport({
+                // see postcss-import docs to learn about onImport param
+                // https://github.com/postcss/postcss-import
+
+                onImport: function (files) {
+                    files.forEach(this.addDependency);
+                }.bind(this)
+            }),
+            autoprefixer
+        ];
+    }
+}
+```
 
 ## Safe Mode
 

index.js

@@ -18,6 +18,10 @@ module.exports = function (source, map) {
     if ( params.safe ) opts.safe = true;
 
     var plugins = this.options.postcss;
+    if ( typeof plugins === 'function' ) {
+        plugins = plugins.call(this);
+    }
+
     if ( typeof plugins === 'undefined' ) {
         plugins = [];
     } else if ( params.pack ) {

test/webpack.config.js

@@ -11,8 +11,10 @@ module.exports = {
         path: path.join(__dirname, '..', 'build'),
         filename: 'test.js'
     },
-    postcss: {
-        defaults: [blue, red],
-        blues:    [blue]
+    postcss: function () {
+        return {
+            defaults: [blue, red],
+            blues:    [blue]
+        };
     }
 };