Development environment improvements (codesandbox#202)

* [dev] Don't show "[HMR]" info messages in the browser's console.

* [dev] Enabled devServer error overlay.

* [dev] Added NoEmitOnErrorsPlugin.

* [dev] Added eslint-loader as a preloader for the main and embed apps.

Author: lbogdan

config/webpack.common.js

@@ -43,6 +43,12 @@ module.exports = {
 
   module: {
     rules: [
+      {
+        test: /\.js$/,
+        loader: 'eslint-loader',
+        enforce: 'pre',
+        include: [paths.appSrc, paths.embedSrc],
+      },
       {
         test: /\.js$/,
         include: paths.src,

config/webpack.dev.js

@@ -22,6 +22,9 @@ module.exports = merge(
     output: {
       filename: 'static/js/[name].js',
     },
-    plugins: [new webpack.HotModuleReplacementPlugin()],
+    plugins: [
+      new webpack.HotModuleReplacementPlugin(),
+      new webpack.NoEmitOnErrorsPlugin(),
+    ],
   }
 );

scripts/start.js

@@ -220,6 +220,8 @@ function runDevServer(port, protocol, index) {
     host: process.env.LOCAL_SERVER ? 'localhost' : 'codesandbox.dev',
     disableHostCheck: !process.env.LOCAL_SERVER,
     contentBase: false,
+    clientLogLevel: 'warning',
+    overlay: true,
   });
 
   // Our custom middleware proxies requests to /index.html or a remote API.