text: // Copyright 2017-2018 Dgraph Labs, Inc. and Contributors
  //
  // Licensed under the Dgraph Community License (the "License"); you
  // may not use this file except in compliance with the License. You
  // may obtain a copy of the License at
  //
  //     https://github.com/dgraph-io/ratel/blob/master/LICENSE
  
  const errorOverlayMiddleware = require("react-dev-utils/errorOverlayMiddleware");
  const noopServiceWorkerMiddleware = require("react-dev-utils/noopServiceWorkerMiddleware");
  const path = require("path");
  const config = require("./webpack.config.dev");
  const paths = require("./paths");
  
  const protocol = process.env.HTTPS === "true" ? "https" : "http";
  const host = process.env.HOST || "0.0.0.0";
  
  module.exports = function(proxy, allowedHost) {
      return {
          // WebpackDevServer 2.4.3 introduced a security fix that prevents remote
          // websites from potentially accessing local content through DNS rebinding:
          // https://github.com/webpack/webpack-dev-server/issues/887
          // https://medium.com/webpack/webpack-dev-server-middleware-security-issues-1489d950874a
          // However, it made several existing use cases such as development in cloud
          // environment or subdomains in development significantly more complicated:
          // https://github.com/facebookincubator/create-react-app/issues/2271
          // https://github.com/facebookincubator/create-react-app/issues/2233
          // While we're investigating better solutions, for now we will take a
          // compromise. Since our WDS configuration only serves files in the `public`
          // folder we won't consider accessing them a vulnerability. However, if you
          // use the `proxy` feature, it gets more dangerous because it can expose
          // remote code execution vulnerabilities in backends like Django and Rails.
          // So we will disable the host check normally, but enable it if you have
          // specified the `proxy` setting. Finally, we let you override it if you
          // really know what you're doing with a special environment variable.
          disableHostCheck:
              !proxy || process.env.DANGEROUSLY_DISABLE_HOST_CHECK === "true",
          // Enable gzip compression of generated files.
          compress: true,
          // Silence WebpackDevServer's own logs since they're generally not useful.
          // It will still show compile warnings and errors with this setting.
          clientLogLevel: "none",
          // By default WebpackDevServer serves physical files from current directory
          // in addition to all the virtual build products that it serves from memory.
          // This is confusing because those files won’t automatically be available in
          // production build folder unless we copy them. However, copying the whole
          // project directory is dangerous because we may expose sensitive files.
          // Instead, we establish a convention that only files in `public` directory
          // get served. Our build script will copy `public` into the `build` folder.
          // In `index.html`, you can get URL of `public` folder with %PUBLIC_URL%:
          // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
          // In JavaScript code, you can access it with `process.env.PUBLIC_URL`.
          // Note that we only recommend to use `public` folder as an escape hatch
          // for files like `favicon.ico`, `manifest.json`, and libraries that are
          // for some reason broken when imported through Webpack. If you just want to
          // use an image, put it in `src` and `import` it from JavaScript instead.
          contentBase: paths.appPublic,
          // By default files from `contentBase` will not trigger a page reload.
          watchContentBase: true,
          // Enable hot reloading server. It will provide /sockjs-node/ endpoint
          // for the WebpackDevServer client so it can learn when the files were
          // updated. The WebpackDevServer client is included as an entry point
          // in the Webpack development configuration. Note that only changes
          // to CSS are currently hot reloaded. JS changes will refresh the browser.
          hot: true,
          // It is important to tell WebpackDevServer to use the same "root" path
          // as we specified in the config. In development, we always serve from /.
          publicPath: config.output.publicPath,
          // WebpackDevServer is noisy by default so we emit custom message instead
          // by listening to the compiler events with `compiler.plugin` calls above.
          quiet: true,
          // Reportedly, this avoids CPU overload on some systems.
          // https://github.com/facebookincubator/create-react-app/issues/293
          // src/node_modules is not ignored to support absolute imports
          // https://github.com/facebookincubator/create-react-app/issues/1065
          watchOptions: {
              ignored: new RegExp(
                  `^(?!${path
                      .normalize(paths.appSrc + "/")
                      .replace(/[\\]+/g, "\\\\")}).+[\\\\/]node_modules[\\\\/]`,
                  "g",
              ),
          },
          // Enable HTTPS if the HTTPS environment variable is set to 'true'
          https: protocol === "https",
          host: host,
          overlay: false,
          historyApiFallback: {
              // Paths with dots should still use the history fallback.
              // See https://github.com/facebookincubator/create-react-app/issues/387.
              disableDotRule: true,
          },
          public: allowedHost,
          proxy,
          before(app) {
              // This lets us open files from the runtime error overlay.
              app.use(errorOverlayMiddleware());
              // This service worker file is effectively a 'no-op' that will reset any
              // previous service worker registered for the same host:port combination.
              // We do this in development to avoid hitting the production cache if
              // it used the same host and port.
              // https://github.com/facebookincubator/create-react-app/issues/2272#issuecomment-302832432
              app.use(noopServiceWorkerMiddleware());
          },
      };
  };
  