详解微信小程序工程化探索之webpack实战

/* 创建项目 */
$ mkdir wxmp-base
$ cd ./wxmp-base
/* 创建package.json */
$ npm init
/* 安装依赖包 */
$ npm install webpack webpack-cli --dev

$ mkdir build
$ cd ./build
$ touch webpack.config.js

/** webpack.config.js */
const path = require('path');
const CopyPlugin = require('copy-webpack-plugin');

const ABSOLUTE_PATH = process.cwd();

module.exports = {
 context: path.resolve(ABSOLUTE_PATH, 'src'),
 entry: {
  app: './app.js',
  'pages/home/index': './pages/home/index.js'
 },
 output: {
  filename: '[name].js',
  path: path.resolve(ABSOLUTE_PATH, 'dist')
 },
 module: {
  rules: [
   {
    test: /\.js$/,
    exclude: /node_modules/,
    use: {
     loader: 'babel-loader',
     options: {
      presets: ['@babel/preset-env'],
      plugins: ['@babel/plugin-transform-runtime'],
     },
    },
   }
  ]
 },
 plugins: [
  new CopyPlugin([
   {
    from: '**/*.wxml',
    toType: 'dir',
   },
   {
    from: '**/*.wxss',
    toType: 'dir',
   },
   {
    from: '**/*.json',
    toType: 'dir',
   }
  ])
 ]
};

/** build/entry-extract-plugin.js */
const fs = require('fs');
const path = require('path');
const chalk = require('chalk');
const replaceExt = require('replace-ext');
const { difference } = require('lodash');
const SingleEntryPlugin = require('webpack/lib/SingleEntryPlugin');
const MultiEntryPlugin = require('webpack/lib/MultiEntryPlugin');

class EntryExtractPlugin {
 constructor() {
  this.appContext = null;
  this.pages = [];
  this.entries = [];
 }

 /**
  * 收集app.json文件中注册的pages和subpackages生成一个待处理数组
  */
 getPages() {
  const app = path.resolve(this.appContext, 'app.json');
  const content = fs.readFileSync(app, 'utf8');
  const { pages = [], subpackages = [] } = JSON.parse(content);
  const { length: pagesLength } = pages;
  if (!pagesLength) {
   console.log(chalk.red('ERROR in "app.json": pages字段缺失'));
   process.exit();
  }
  /** 收集分包中的页面 */
  const { length: subPackagesLength } = subpackages;
  if (subPackagesLength) {
   subpackages.forEach((subPackage) => {
    const { root, pages: subPages = [] } = subPackage;
    if (!root) {
     console.log(chalk.red('ERROR in "app.json": 分包配置中root字段缺失'));
     process.exit();
    }
    const { length: subPagesLength } = subPages;
    if (!subPagesLength) {
     console.log(chalk.red(`ERROR in "app.json": 当前分包 "${root}" 中pages字段为空`));
     process.exit();
    }
    subPages.forEach((subPage) => pages.push(`${root}/${subPage}`));
   });
  }
  return pages;
 }

 /**
  * 以页面为起始点递归去寻找所使用的组件
  * @param {String} 当前文件的上下文路径
  * @param {String} 依赖路径
  * @param {Array} 包含全部入口的数组
  */
 addDependencies(context, dependPath, entries) {
  /** 生成绝对路径 */
  const isAbsolute = dependPath[0] === '/';
  let absolutePath = '';
  if (isAbsolute) {
   absolutePath = path.resolve(this.appContext, dependPath.slice(1));
  } else {
   absolutePath = path.resolve(context, dependPath);
  }
  /** 生成以源代码目录为基准的相对路径 */
  const relativePath = path.relative(this.appContext, absolutePath);
  /** 校验该路径是否合法以及是否在已有入口当中 */
  const jsPath = replaceExt(absolutePath, '.js');
  const isQualification = fs.existsSync(jsPath);
  if (!isQualification) {
   console.log(chalk.red(`ERROR: in "${replaceExt(relativePath, '.js')}": 当前文件缺失`));
   process.exit();
  }
  const isExistence = entries.includes((entry) => entry === absolutePath);
  if (!isExistence) {
   entries.push(relativePath);
  }
  /** 获取json文件内容 */
  const jsonPath = replaceExt(absolutePath, '.json');
  const isJsonExistence = fs.existsSync(jsonPath);
  if (!isJsonExistence) {
   console.log(chalk.red(`ERROR: in "${replaceExt(relativePath, '.json')}": 当前文件缺失`));
   process.exit();
  }
  try {
   const content = fs.readFileSync(jsonPath, 'utf8');
   const { usingComponents = {} } = JSON.parse(content);
   const components = Object.values(usingComponents);
   const { length } = components;
   /** 当json文件中有再引用其他组件时执行递归 */
   if (length) {
    const absoluteDir = path.dirname(absolutePath);
    components.forEach((component) => {
     this.addDependencies(absoluteDir, component, entries);
    });
   }
  } catch (e) {
   console.log(chalk.red(`ERROR: in "${replaceExt(relativePath, '.json')}": 当前文件内容为空或书写不正确`));
   process.exit();
  }
 }

 /**
  * 将入口加入到webpack中
  */
 applyEntry(context, entryName, module) {
  if (Array.isArray(module)) {
   return new MultiEntryPlugin(context, module, entryName);
  }
  return new SingleEntryPlugin(context, module, entryName);
 }

 apply(compiler) {
  /** 设置源代码的上下文 */
  const { context } = compiler.options;
  this.appContext = context;

  compiler.hooks.entryOption.tap('EntryExtractPlugin', () => {
   /** 生成入口依赖数组 */
   this.pages = this.getPages();
   this.pages.forEach((page) => void this.addDependencies(context, page, this.entries));
   this.entries.forEach((entry) => {
    this.applyEntry(context, entry, `./${entry}`).apply(compiler);
   });
  });

  compiler.hooks.watchRun.tap('EntryExtractPlugin', () => {
   /** 校验页面入口是否增加 */
   const pages = this.getPages();
   const diffPages = difference(pages, this.pages);
   const { length } = diffPages;
   if (length) {
    this.pages = this.pages.concat(diffPages);
    const entries = [];
    /** 通过新增的入口页面建立依赖 */
    diffPages.forEach((page) => void this.addDependencies(context, page, entries));
    /** 去除与原有依赖的交集 */
    const diffEntries = difference(entries, this.entries);
    diffEntries.forEach((entry) => {
     this.applyEntry(context, entry, `./${entry}`).apply(compiler);
    });
    this.entries = this.entries.concat(diffEntries);
   }
  });
 }
}

module.exports = EntryExtractPlugin;

/** build/webpack.config.js */
const EntryExtractPlugin = require('./entry-extract-plugin');

module.exports = {
 ...
 entry: {
  app: './app.js'
 },
 plugins: [
  ...
  new EntryExtractPlugin()
 ]
}

/** build/webpack.config.js */
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
 ...
 module: {
  rules: [
   ...
   {
    enforce: 'pre',
    test: /\.js$/,
    exclude: /node_modules/,
    loader: 'eslint-loader',
    options: {
     cache: true,
     fix: true,
    },
   },
   {
    test: /\.less$/,
    use: [
     {
      loader: MiniCssExtractPlugin.loader,
     },
     {
      loader: 'css-loader',
     },
     {
      loader: 'less-loader',
     },
    ],
   },
  ]
 },
 plugins: [
  ...
  new MiniCssExtractPlugin({ filename: '[name].wxss' })
 ]
}

"scripts": {
 "dev": "cross-env OPERATING_ENV=development webpack --config build/webpack.config.js --watch",
 "build": "cross-env OPERATING_ENV=production webpack --config build/webpack.config.js
}

/** build/webpack.config.js */
const { OPERATING_ENV } = process.env;

module.exports = {
 ...
 mode: OPERATING_ENV,
 devtool: OPERATING_ENV === 'production' ? 'source-map' : 'inline-source-map'
}

/** build/webpack.config.js */
module.exports = {
 ...
 optimization: {
  splitChunks: {
   cacheGroups: {
    commons: {
     chunks: 'initial',
     name: 'commons',
     minSize: 0,
     maxSize: 0,
     minChunks: 2,
    },
   },
  },
  runtimeChunk: {
   name: 'manifest',
  },
 },
}

/** build/webpack.config.js */
module.exports = {
 ...
 output: {
  ...
  globalObject: 'global'
 },
 plugins: [
  new webpack.BannerPlugin({
   banner: 'const commons = require("./commons");\nconst runtime = require("./runtime");',
   raw: true,
   include: 'app.js',
  })
 ]
}