Merge pull request #115 from storybooks/middleware

Support custom middleware

src/server/middleware.js

@@ -1,3 +1,5 @@
+import fs from 'fs';
+import path from 'path';
 import { Router } from 'express';
 import webpack from 'webpack';
 import webpackDevMiddleware from 'webpack-dev-middleware';
@@ -6,6 +8,18 @@ import baseConfig from './config/webpack.config';
 import loadConfig from './config';
 import getIndexHtml from './index.html';
 
+function getMiddleware(configDir) {
+  const middlewarePath = path.resolve(configDir, 'middleware.js');
+  if (fs.existsSync(middlewarePath)) {
+    let middlewareModule = require(middlewarePath);
+    if (middlewareModule.__esModule) {
+      middlewareModule = middlewareModule.default;
+    }
+    return middlewareModule;
+  }
+  return function () {};
+}
+
 export default function (configDir) {
   // Build the webpack configuration using the `baseConfig`
   // custom `.babelrc` file and `webpack.config.js` files
@@ -25,6 +39,9 @@ export default function (configDir) {
   };
 
   const router = new Router();
+  const middlewareFn = getMiddleware(configDir);
+  middlewareFn(router);
+
   router.use(webpackDevMiddleware(compiler, devMiddlewareOptions));
   router.use(webpackHotMiddleware(compiler));