實戰篇---微信小程式工程化探索之webpack

/* 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复制代码

/** 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;复制代码

/** build/webpack.config.js */const EntryExtractPlugin = require('./entry-extract-plugin');module.exports = {
  ...
  entry: {    app: './app.js'
  },  plugins: [
    ...
    new EntryExtractPlugin()
  ]
}复制代码

/** 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' })
  ]
}复制代码

"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
}复制代码

/** build/webpack.config.js */const { OPERATING_ENV } = process.env;module.exports = {
  ...
  mode: OPERATING_ENV,  devtool: OPERATING_ENV === 'production' ? 'source-map' : 'inline-source-map'}复制代码

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

/** 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',
    })
  ]
}复制代码