# wepack源码 Compiler

class Compiler
/lib/compiler.js
是一个全局单例，负责构建整个打包流程

# constructor()

里面有一堆钩子🐶

constructor(context) {
    this.hooks = Object.freeze({
			initialize: new SyncHook([]),
			shouldEmit: new SyncBailHook(["compilation"]),
			done: new AsyncSeriesHook(["stats"]),
			afterDone: new SyncHook(["stats"]),
			additionalPass: new AsyncSeriesHook([]),
			beforeRun: new AsyncSeriesHook(["compiler"]),
			run: new AsyncSeriesHook(["compiler"]),
			emit: new AsyncSeriesHook(["compilation"]),
			assetEmitted: new AsyncSeriesHook(["file", "info"]),
			afterEmit: new AsyncSeriesHook(["compilation"]),
    ...}
}

# func run()

Compiler.run()开跑
beforeRun 来自async + require("tapable")处理缓存的模块，之后才compile()
compile()结束后回调 onCompiled 将编译后的内容生成文件
shouldEmit判断是否编译成功

	run(callback) {
        const onCompiled = (err, compilation) => {
			if (err) return finalCallback(err);

			if (this.hooks.shouldEmit.call(compilation) === false) {
                ...}
            }
        ...
		const run = () => {
			this.hooks.beforeRun.callAsync(this, err => {
                ...
				this.hooks.run.callAsync(this, err => {
                    ...
					this.readRecords(err => {
                        ...
						this.compile(onCompiled);
					});
				});
			});
		};
    }

# func compile()

编译过程

compile(callback){
	const params = this.newCompilationParams();
    this.hooks.beforeCompile.callAsync(params, err => { // 会回调
    ...
			// 这个钩子会触发entryplugin的make回调
			this.hooks.make.callAsync(compilation, err => { // 开始编译
					
					this.hooks.finishMake.callAsync(compilation, err => {
                    ...
					    process.nextTick(() => {
    						compilation.finish(err => {
							    compilation.seal(err => { // 封装


    
        }

    }
}

# func newCompilationParams

params 模块工厂传入钩子，方便之后的插件或钩子操作模块

	newCompilationParams() {
		const params = {
			normalModuleFactory: this.createNormalModuleFactory(),
			contextModuleFactory: this.createContextModuleFactory()
		};
		return params;
	}