Support proxy setting in elm-package.json

config/paths.js

@@ -8,4 +8,4 @@ module.exports = {
   ownModules: path.resolve(__dirname, '../node_modules'),
   scripts: path.resolve(__dirname, '../scripts'),
   elmMake: path.resolve(__dirname, '../node_modules/.bin/elm-make')
-};
+};

package.json

@@ -43,6 +43,7 @@
     "chalk": "1.1.3",
     "clean-webpack-plugin": "0.1.14",
     "cli-table": "0.3.1",
+    "connect-history-api-fallback": "^1.3.0",
     "cross-spawn": "5.0.1",
     "css-loader": "0.26.1",
     "dotenv": "^2.0.0",
@@ -55,6 +56,7 @@
     "file-loader": "0.9.0",
     "fs-extra": "1.0.0",
     "html-webpack-plugin": "2.24.1",
+    "http-proxy-middleware": "^0.17.3",
     "minimist": "1.2.0",
     "path-exists": "3.0.0",
     "postcss-loader": "1.2.1",

scripts/start.js

@@ -1,8 +1,4 @@
-process.env.NODE_ENV = 'development';
-// Load environment variables from .env file.
-// Suppress warnings if this file is missing.
-require('dotenv').config({silent: true});
-
+const fs = require('fs');
 const pathExists = require('path-exists');
 const chalk = require('chalk');
 const webpack = require('webpack');
@@ -11,6 +7,12 @@ const config = require('../config/webpack.config.dev');
 const formatWebpackMessages = require('react-dev-utils/formatWebpackMessages');
 const clearConsole = require('react-dev-utils/clearConsole');
 const openBrowser = require('react-dev-utils/openBrowser');
+const historyApiFallback = require('connect-history-api-fallback');
+const httpProxyMiddleware = require('http-proxy-middleware');
+
+// Load environment variables from .env file.
+// Suppress warnings if this file is missing.
+require('dotenv').config({silent: true});
 
 if (pathExists.sync('elm-package.json') === false) {
   console.log('Please, run the build script from project root directory');
@@ -54,14 +56,108 @@ compiler.plugin('done', function (stats) {
   }
 });
 
+
+// We need to provide a custom onError function for httpProxyMiddleware.
+// It allows us to log custom error messages on the console.
+function onProxyError(proxy) {
+  return function(err, req, res){
+    var host = req.headers && req.headers.host;
+    console.log(
+      chalk.red('Proxy error:') + ' Could not proxy request ' + chalk.cyan(req.url) +
+      ' from ' + chalk.cyan(host) + ' to ' + chalk.cyan(proxy) + '.'
+    );
+    console.log(
+      'See https://nodejs.org/api/errors.html#errors_common_system_errors for more information (' +
+      chalk.cyan(err.code) + ').'
+    );
+    console.log();
+
+    // And immediately send the proper error response to the client.
+    // Otherwise, the request will eventually timeout with ERR_EMPTY_RESPONSE on the client side.
+    if (res.writeHead && !res.headersSent) {
+        res.writeHead(500);
+    }
+    res.end('Proxy error: Could not proxy request ' + req.url + ' from ' +
+      host + ' to ' + proxy + ' (' + err.code + ').'
+    );
+  };
+}
+
+function addMiddleware(devServer) {
+  // `proxy` lets you to specify a fallback server during development.
+  // Every unrecognized request will be forwarded to it.
+  var proxy = JSON.parse(fs.readFileSync('elm-package.json', 'utf-8')).proxy;
+  devServer.use(historyApiFallback({
+    // Paths with dots should still use the history fallback.
+    // See https://github.com/facebookincubator/create-react-app/issues/387.
+    disableDotRule: true,
+    // For single page apps, we generally want to fallback to /index.html.
+    // However we also want to respect `proxy` for API calls.
+    // So if `proxy` is specified, we need to decide which fallback to use.
+    // We use a heuristic: if request `accept`s text/html, we pick /index.html.
+    // Modern browsers include text/html into `accept` header when navigating.
+    // However API calls like `fetch()` won’t generally accept text/html.
+    // If this heuristic doesn’t work well for you, don’t use `proxy`.
+    htmlAcceptHeaders: proxy ?
+      [ 'text/html' ] :
+      [ 'text/html', '*/*' ]
+  }));
+  if (proxy) {
+    if (typeof proxy !== 'string') {
+      console.log(chalk.red('When specified, "proxy" in package.json must be a string.'));
+      console.log(chalk.red('Instead, the type of "proxy" was "' + typeof proxy + '".'));
+      console.log(chalk.red('Either remove "proxy" from package.json, or make it a string.'));
+      process.exit(1);
+    }
+
+    // Otherwise, if proxy is specified, we will let it handle any request.
+    // There are a few exceptions which we won't send to the proxy:
+    // - /index.html (served as HTML5 history API fallback)
+    // - /*.hot-update.json (WebpackDevServer uses this too for hot reloading)
+    // - /sockjs-node/* (WebpackDevServer uses this for hot reloading)
+    // Tip: use https://jex.im/regulex/ to visualize the regex
+    var mayProxy = /^(?!\/(index\.html$|.*\.hot-update\.json$|sockjs-node\/)).*$/;
+
+    // Pass the scope regex both to Express and to the middleware for proxying
+    // of both HTTP and WebSockets to work without false positives.
+    var hpm = httpProxyMiddleware(pathname => mayProxy.test(pathname), {
+      target: proxy,
+      logLevel: 'silent',
+      onProxyReq: function(proxyReq) {
+        // Browers may send Origin headers even with same-origin
+        // requests. To prevent CORS issues, we have to change
+        // the Origin to match the target URL.
+        if (proxyReq.getHeader('origin')) {
+          proxyReq.setHeader('origin', proxy);
+        }
+      },
+      onError: onProxyError(proxy),
+      secure: false,
+      changeOrigin: true,
+      ws: true
+    });
+    devServer.use(mayProxy, hpm);
+
+    // Listen for the websocket 'upgrade' event and upgrade the connection.
+    // If this is not done, httpProxyMiddleware will not try to upgrade until
+    // an initial plain HTTP request is made.
+    devServer.listeningApp.on('upgrade', hpm.upgrade);
+  }
+
+  // Finally, by now we have certainly resolved the URL.
+  // It may be /index.html, so let the dev server try serving it again.
+  devServer.use(devServer.middleware);
+}
+
 const devServer = new WebpackDevServer(compiler, {
   hot: true,
   inline: true,
   publicPath: '/',
-  quiet: true,
-  historyApiFallback: true,
+  quiet: true
 });
 
+addMiddleware(devServer);
+
 // Launch WebpackDevServer.
 devServer.listen(port, function (err) {
   if (err) {

yarn.lock

@@ -1584,7 +1584,7 @@ http-errors@~1.5.0:
     setprototypeof "1.0.2"
     statuses ">= 1.3.1 < 2"
 
-http-proxy-middleware@~0.17.1:
+http-proxy-middleware@^0.17.3, http-proxy-middleware@~0.17.1:
   version "0.17.3"
   resolved "https://registry.yarnpkg.com/http-proxy-middleware/-/http-proxy-middleware-0.17.3.tgz#940382147149b856084f5534752d5b5a8168cd1d"
   dependencies: