Prototype of web-based preview for subassemblies

asp-review-app/ui/scripts/start.js

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+'use strict';
+
+// Do this as the first thing so that any code reading it knows the right env.
+process.env.BABEL_ENV = 'development';
+process.env.NODE_ENV = 'development';
+
+// Makes the script crash on unhandled rejections instead of silently
+// ignoring them. In the future, promise rejections that are not handled will
+// terminate the Node.js process with a non-zero exit code.
+process.on('unhandledRejection', err => {
+  throw err;
+});
+
+// Ensure environment variables are read.
+require('../config/env');
+
+const fs = require('fs');
+const chalk = require('react-dev-utils/chalk');
+const webpack = require('webpack');
+const WebpackDevServer = require('webpack-dev-server');
+const clearConsole = require('react-dev-utils/clearConsole');
+const checkRequiredFiles = require('react-dev-utils/checkRequiredFiles');
+const {
+  choosePort,
+  createCompiler,
+  prepareProxy,
+  prepareUrls,
+} = require('react-dev-utils/WebpackDevServerUtils');
+const openBrowser = require('react-dev-utils/openBrowser');
+const semver = require('semver');
+const paths = require('../config/paths');
+const configFactory = require('../config/webpack.config');
+const createDevServerConfig = require('../config/webpackDevServer.config');
+const getClientEnvironment = require('../config/env');
+const react = require(require.resolve('react', { paths: [paths.appPath] }));
+
+const env = getClientEnvironment(paths.publicUrlOrPath.slice(0, -1));
+const useYarn = fs.existsSync(paths.yarnLockFile);
+const isInteractive = process.stdout.isTTY;
+
+// Warn and crash if required files are missing
+if (!checkRequiredFiles([paths.appHtml, paths.appIndexJs])) {
+  process.exit(1);
+}
+
+// Tools like Cloud9 rely on this.
+const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 3000;
+const HOST = process.env.HOST || '0.0.0.0';
+
+if (process.env.HOST) {
+  console.log(
+    chalk.cyan(
+      `Attempting to bind to HOST environment variable: ${chalk.yellow(
+        chalk.bold(process.env.HOST)
+      )}`
+    )
+  );
+  console.log(
+    `If this was unintentional, check that you haven't mistakenly set it in your shell.`
+  );
+  console.log(
+    `Learn more here: ${chalk.yellow('https://cra.link/advanced-config')}`
+  );
+  console.log();
+}
+
+// We require that you explicitly set browsers and do not fall back to
+// browserslist defaults.
+const { checkBrowsers } = require('react-dev-utils/browsersHelper');
+checkBrowsers(paths.appPath, isInteractive)
+  .then(() => {
+    // We attempt to use the default port but if it is busy, we offer the user to
+    // run on a different port. `choosePort()` Promise resolves to the next free port.
+    return choosePort(HOST, DEFAULT_PORT);
+  })
+  .then(port => {
+    if (port == null) {
+      // We have not found a port.
+      return;
+    }
+
+    const config = configFactory('development');
+    const protocol = process.env.HTTPS === 'true' ? 'https' : 'http';
+    const appName = require(paths.appPackageJson).name;
+
+    const useTypeScript = fs.existsSync(paths.appTsConfig);
+    const urls = prepareUrls(
+      protocol,
+      HOST,
+      port,
+      paths.publicUrlOrPath.slice(0, -1)
+    );
+    // Create a webpack compiler that is configured with custom messages.
+    const compiler = createCompiler({
+      appName,
+      config,
+      urls,
+      useYarn,
+      useTypeScript,
+      webpack,
+    });
+    // Load proxy config
+    const proxySetting = require(paths.appPackageJson).proxy;
+    const proxyConfig = prepareProxy(
+      proxySetting,
+      paths.appPublic,
+      paths.publicUrlOrPath
+    );
+    // Serve webpack assets generated by the compiler over a web server.
+    const serverConfig = {
+      ...createDevServerConfig(proxyConfig, urls.lanUrlForConfig),
+      host: HOST,
+      port,
+    };
+    const devServer = new WebpackDevServer(serverConfig, compiler);
+    // Launch WebpackDevServer.
+    devServer.startCallback(() => {
+      if (isInteractive) {
+        clearConsole();
+      }
+
+      if (env.raw.FAST_REFRESH && semver.lt(react.version, '16.10.0')) {
+        console.log(
+          chalk.yellow(
+            `Fast Refresh requires React 16.10 or higher. You are using React ${react.version}.`
+          )
+        );
+      }
+
+      console.log(chalk.cyan('Starting the development server...\n'));
+      openBrowser(urls.localUrlForBrowser);
+    });
+
+    ['SIGINT', 'SIGTERM'].forEach(function (sig) {
+      process.on(sig, function () {
+        devServer.close();
+        process.exit();
+      });
+    });
+
+    if (process.env.CI !== 'true') {
+      // Gracefully exit when stdin ends
+      process.stdin.on('end', function () {
+        devServer.close();
+        process.exit();
+      });
+    }
+  })
+  .catch(err => {
+    if (err && err.message) {
+      console.log(err.message);
+    }
+    process.exit(1);
+  });