creatreactapp3-配置文件分析1eject之后

菜鸟学习 react 中，配置文件有点乱，研究一波。

yarn eject 之后，文件目录相比之前只是多了 config 和 scripts 两个文件夹，package.json 多了很多配置项, 所以本文主要解决 config 和 package.json 两个部分.

一.config 文件夹下，还有一个 jest 文件夹是 jest 测试文件，cssTransform.js 和 fileTransform.js 对应 package.json 中的

"transform": {"^.+\\.(js|jsx|ts|tsx)$": "<rootDir>/node_modules/babel-jest",
      "^.+\\.css$": "<rootDir>/config/jest/cssTransform.js",
      "^(?!.*\\.(js|jsx|ts|tsx|css|json)$)": "<rootDir>/config/jest/fileTransform.js"
    },

二. 重点分析，从 package.json 命令行入手，

"scripts": {
    "start": "node scripts/start.js",
    "build": "node scripts/build.js",
    "test": "node scripts/test.js"
  },

看命令就知道 scripts 下的三个文件，分别对应开发，打包和测试三个环境的入口。

config/path.js 里面路径变量

const resolveApp = relativePath => path.resolve(appDirectory, relativePath);// 解析对应文件的绝对路径
const getPublicUrl = appPackageJson =>
  envPublicUrl || require(appPackageJson).homepage;// 赋值下面变量 publicUrl，从 env.js 或者 package.json 中获取 homepage
function getServedPath(appPackageJson) {const publicUrl = getPublicUrl(appPackageJson);
  const servedUrl =
    envPublicUrl || (publicUrl ? url.parse(publicUrl).pathname : '/');
  return ensureSlash(servedUrl, true);
}// 服务域名
  


----------


  dotenv: resolveApp('.env'),
  appPath: resolveApp('.'),
  appBuild: resolveApp('build'),
  appPublic: resolveApp('public'),
  appHtml: resolveApp('public/index.html'),
  appIndexJs: resolveModule(resolveApp, 'src/index'),
  appPackageJson: resolveApp('package.json'),
  appSrc: resolveApp('src'),
  appTsConfig: resolveApp('tsconfig.json'),
  appJsConfig: resolveApp('jsconfig.json'),
  yarnLockFile: resolveApp('yarn.lock'),
  testsSetup: resolveModule(resolveApp, 'src/setupTests'),
  proxySetup: resolveApp('src/setupProxy.js'),
  appNodeModules: resolveApp('node_modules'),
  publicUrl: getPublicUrl(resolveApp('package.json')),
  servedPath: getServedPath(resolveApp('package.json')),

---

1.start.js 其实就是开发环境 devserver 的配置和启动

process.env.BABEL_ENV = 'development';//bebel 用到环境变量 (@babel/preset-react)
process.env.NODE_ENV = 'development';// 全局 node 环境变量


process.on('unhandledRejection', err => {throw err;});

// Ensure environment variables are read.
require('../config/env');// 开发环境配置文件


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');


----------


//TODO 下面就是对应 devserver 的详细配置了，open,host,port,http,proxy 等，都是从对应的文件中读取，env.js，package.json 等

const openBrowser = require('react-dev-utils/openBrowser');
const paths = require('../config/paths');
const configFactory = require('../config/webpack.config');//webpack 对应环境配置的函数
const createDevServerConfig = require('../config/webpackDevServer.config');
//devserver 的配置文件
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://bit.ly/CRA-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);
    const devSocket = {
      warnings: warnings =>
        devServer.sockWrite(devServer.sockets, 'warnings', warnings),
      errors: errors =>
        devServer.sockWrite(devServer.sockets, 'errors', errors),
    };
    // Create a webpack compiler that is configured with custom messages.
    const compiler = createCompiler({
      appName,
      config,
      devSocket,
      urls,
      useYarn,
      useTypeScript,
      webpack,
    });
    // Load proxy config
    const proxySetting = require(paths.appPackageJson).proxy;
    const proxyConfig = prepareProxy(proxySetting, paths.appPublic);
    // Serve webpack assets generated by the compiler over a web server.
    const serverConfig = createDevServerConfig(
      proxyConfig,
      urls.lanUrlForConfig
    );
    
    


----------
     //TODO devserver 开发服务启动

    const devServer = new WebpackDevServer(compiler, serverConfig);
    // Launch WebpackDevServer.
    
   
    devServer.listen(port, HOST, err => {if (err) {return console.log(err);
      }
      if (isInteractive) {clearConsole();
      }

      // We used to support resolving modules according to `NODE_PATH`.
      // This now has been deprecated in favor of jsconfig/tsconfig.json
      // This lets you use absolute paths in imports inside large monorepos:
      if (process.env.NODE_PATH) {
        console.log(
          chalk.yellow('Setting NODE_PATH to resolve modules absolutely has been deprecated in favor of setting baseUrl in jsconfig.json (or tsconfig.json if you are using TypeScript) and will be removed in a future major release of create-react-app.'
          )
        );
        console.log();}

      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();});
    });
  })
  .catch(err => {if (err && err.message) {console.log(err.message);
    }
    process.exit(1);
  });