Add ignoreOrder option to avoid the OrderUndefinedError

index.js

@@ -289,7 +289,7 @@ ExtractTextPlugin.prototype.apply = function(compiler) {
 			extractedChunks.forEach(function(extractedChunk) {
 				if(extractedChunk.modules.length) {
 					extractedChunk.modules.sort(function(a, b) {
-						if(isInvalidOrder(a, b)) {
+						if(!options.ignoreOrder && isInvalidOrder(a, b)) {
 							compilation.errors.push(new OrderUndefinedError(a.getOriginalModule()));
 							compilation.errors.push(new OrderUndefinedError(b.getOriginalModule()));
 						}

test/cases/order-undefined-error/a.css

@@ -0,0 +1,4 @@
+.a {
+  composes: c1 from './c1.css';
+  composes: c2 from './c2.css';
+}

test/cases/order-undefined-error/b.css

@@ -0,0 +1,4 @@
+.b {
+  composes: c2 from './c2.css';
+  composes: c1 from './c1.css';
+}

test/cases/order-undefined-error/c1.css

@@ -0,0 +1,2 @@
+.c1 {
+}

test/cases/order-undefined-error/c2.css

@@ -0,0 +1,2 @@
+.c2 {
+}

test/cases/order-undefined-error/expected/file.css

@@ -0,0 +1,8 @@
+._3QiTkN7JPds2C9Bq73MpOX {
+}
+._3dtwYD12yqGZUJ-uPQLu9z {
+}
+._32HVXkGocfWZMaHoXEFkED {
+}
+.hbZI7DlQBB9VYNCgL20kL {
+}

test/cases/order-undefined-error/index.js

@@ -0,0 +1,2 @@
+require('./a.css');
+require('./b.css');

test/cases/order-undefined-error/webpack.config.js

@@ -0,0 +1,15 @@
+var ExtractTextPlugin = require("../../../");
+module.exports = {
+  entry: "./index.js",
+  module: {
+    loaders: [{
+      test: /\.css$/,
+      loader: ExtractTextPlugin.extract('style', 'css?modules')
+    }]
+  },
+  plugins: [
+    new ExtractTextPlugin('file.css', {
+      ignoreOrder: true
+    })
+  ]
+}