浅析webpack源码之NodeEnvironmentPlugin模块总览（六）

进入webpack.js//传入地址,new Compiler出来一个复杂对象compiler = new Compiler(options.context);// 把options挂载到对象上compiler.options = options;new NodeEnvironmentPlugin().apply(compiler);compiler太复杂我们先看NodeEnvironmentPluginconst NodeWatchFileSystem = require("./NodeWatchFileSystem");const NodeOutputFileSystem = require("./NodeOutputFileSystem");const NodeJsInputFileSystem = require(“enhanced-resolve/lib/NodeJsInputFileSystem”);const CachedInputFileSystem = require(“enhanced-resolve/lib/CachedInputFileSystem”);class NodeEnvironmentPlugin { apply(compiler) { // 可以缓存输入的文件系统 compiler.inputFileSystem = new CachedInputFileSystem( new NodeJsInputFileSystem(), 60000 ); // 输入文件系统 const inputFileSystem = compiler.inputFileSystem; // 输出文件系统，挂载到compiler对象 compiler.outputFileSystem = new NodeOutputFileSystem(); // 传入输入文件，监视文件系统，挂载到compiler对象 compiler.watchFileSystem = new NodeWatchFileSystem( compiler.inputFileSystem ); // 添加事件流before-run compiler.hooks.beforeRun.tap(“NodeEnvironmentPlugin”, compiler => { if (compiler.inputFileSystem === inputFileSystem) inputFileSystem.purge(); }); }}module.exports = NodeEnvironmentPlugin;打开插件NodeJsInputFileSystem.js"use strict";const fs = require(“graceful-fs”);class NodeJsInputFileSystem { //读取目录下文件 readdir(path, callback) { fs.readdir(path, (err, files) => { callback(err, files && files.map(file => { // 对文件名进行NFC格式化 return file.normalize ? file.normalize(“NFC”) : file; })); }); } //异步读取目录下文件 readdirSync(path) { const files = fs.readdirSync(path); return files && files.map(file => { return file.normalize ? file.normalize(“NFC”) : file; }); }}const fsMethods = [ “stat”, “statSync”, “readFile”, “readFileSync”, “readlink”, “readlinkSync”];// 同步fs方法for(const key of fsMethods) { Object.defineProperty(NodeJsInputFileSystem.prototype, key, { configurable: true, writable: true, value: fs[key].bind(fs) });}module.exports = NodeJsInputFileSystem;graceful-fs就是对node 原生fs 做了一层封装，显得更优雅总体看来NodeEnvironmentPlugin这个模块就是对文件做了处理，又重新封装了node.js 对fs模块做了以一些处理，文件的输入，输出，缓存，监听…