vue源码解析入口文件

为了加深对vue的理解，之前我们实现了一版mini-vue现在我们来看真正的vue源码来看下到底vue是如何实现的.

准备工作

首先我们将vue源码下载到本地，我现在使用的是2.6.14版本，可以从github上fork仓库到自己的github上，之后方便我们添加注释重新push到github上。

代码下载到本地之后 我们看package.json文件

{
  "name": "vue",
  "version": "2.6.14",
  "description": "Reactive, component-oriented view layer for modern web interfaces.",
  "main": "dist/vue.runtime.common.js",
  "module": "dist/vue.runtime.esm.js",
  "unpkg": "dist/vue.js",
  "jsdelivr": "dist/vue.js",
  "typings": "types/index.d.ts",
  "files": [
    "src",
    "dist/*.js",
    "types/*.d.ts"
  ],
  "sideEffects": false,
  "scripts": {
    "dev": "rollup -w -c scripts/config.js --environment TARGET:web-full-dev",
    "dev:cjs": "rollup -w -c scripts/config.js --environment TARGET:web-runtime-cjs-dev",
    "dev:esm": "rollup -w -c scripts/config.js --environment TARGET:web-runtime-esm",
    "dev:test": "karma start test/unit/karma.dev.config.js",
    "dev:ssr": "rollup -w -c scripts/config.js --environment TARGET:web-server-renderer",
    "dev:compiler": "rollup -w -c scripts/config.js --environment TARGET:web-compiler ",
    "dev:weex": "rollup -w -c scripts/config.js --environment TARGET:weex-framework",
    "dev:weex:factory": "rollup -w -c scripts/config.js --environment TARGET:weex-factory",
    "dev:weex:compiler": "rollup -w -c scripts/config.js --environment TARGET:weex-compiler ",
    "build": "node scripts/build.js",
    "build:ssr": "npm run build -- web-runtime-cjs,web-server-renderer",
    "build:weex": "npm run build -- weex",
    "test": "npm run lint && flow check && npm run test:types && npm run test:cover && npm run test:e2e -- --env phantomjs && npm run test:ssr && npm run test:weex",
    "test:unit": "karma start test/unit/karma.unit.config.js",
    "test:cover": "karma start test/unit/karma.cover.config.js",
    "test:e2e": "npm run build -- web-full-prod,web-server-basic-renderer && node test/e2e/runner.js",
    "test:weex": "npm run build:weex && jasmine JASMINE_CONFIG_PATH=test/weex/jasmine.js",
    "test:ssr": "npm run build:ssr && jasmine JASMINE_CONFIG_PATH=test/ssr/jasmine.js",
    "test:sauce": "npm run sauce -- 0 && npm run sauce -- 1 && npm run sauce -- 2",
    "test:types": "tsc -p ./types/test/tsconfig.json",
    "lint": "eslint src scripts test",
    "flow": "flow check",
    "sauce": "karma start test/unit/karma.sauce.config.js",
    "bench:ssr": "npm run build:ssr && node benchmarks/ssr/renderToString.js && node benchmarks/ssr/renderToStream.js",
    "release": "bash scripts/release.sh",
    "release:weex": "bash scripts/release-weex.sh",
    "release:note": "node scripts/gen-release-note.js",
    "commit": "git-cz"
  },
  "gitHooks": {
    "pre-commit": "lint-staged",
    "commit-msg": "node scripts/verify-commit-msg.js"
  },
  "lint-staged": {
    "*.js": [
      "eslint --fix",
      "git add"
    ]
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/vuejs/vue.git"
  },
  "keywords": [
    "vue"
  ],
  "author": "Evan You",
  "license": "MIT",
  "bugs": {
    "url": "https://github.com/vuejs/vue/issues"
  },
  "homepage": "https://github.com/vuejs/vue#readme",
  "devDependencies": {
    "@babel/core": "^7.0.0",
    "@babel/plugin-proposal-class-properties": "^7.1.0",
    "@babel/plugin-syntax-dynamic-import": "^7.0.0",
    "@babel/plugin-syntax-jsx": "^7.0.0",
    "@babel/plugin-transform-flow-strip-types": "^7.0.0",
    "@babel/preset-env": "^7.0.0",
    "@babel/register": "^7.0.0",
    "@types/node": "^12.12.0",
    "@types/webpack": "^4.4.22",
    "acorn": "^5.2.1",
    "babel-eslint": "^10.0.1",
    "babel-helper-vue-jsx-merge-props": "^2.0.3",
    "babel-loader": "^8.0.4",
    "babel-plugin-istanbul": "^5.1.0",
    "babel-plugin-transform-vue-jsx": "^4.0.1",
    "babel-preset-flow-vue": "^1.0.0",
    "buble": "^0.19.3",
    "chalk": "^2.3.0",
    "chromedriver": "^2.45.0",
    "codecov": "^3.0.0",
    "commitizen": "^2.9.6",
    "conventional-changelog": "^1.1.3",
    "cross-spawn": "^6.0.5",
    "cz-conventional-changelog": "^2.0.0",
    "de-indent": "^1.0.2",
    "es6-promise": "^4.1.0",
    "escodegen": "^1.8.1",
    "eslint": "^5.7.0",
    "eslint-plugin-flowtype": "^2.34.0",
    "eslint-plugin-jasmine": "^2.8.4",
    "file-loader": "^3.0.1",
    "flow-bin": "^0.61.0",
    "hash-sum": "^1.0.2",
    "he": "^1.1.1",
    "http-server": "^0.12.3",
    "jasmine": "^2.99.0",
    "jasmine-core": "^2.99.0",
    "karma": "^3.1.1",
    "karma-chrome-launcher": "^2.1.1",
    "karma-coverage": "^1.1.1",
    "karma-firefox-launcher": "^1.0.1",
    "karma-jasmine": "^1.1.0",
    "karma-mocha-reporter": "^2.2.3",
    "karma-phantomjs-launcher": "^1.0.4",
    "karma-safari-launcher": "^1.0.0",
    "karma-sauce-launcher": "^2.0.2",
    "karma-sourcemap-loader": "^0.3.7",
    "karma-webpack": "^4.0.0-rc.2",
    "lint-staged": "^8.0.0",
    "lodash": "^4.17.4",
    "lodash.template": "^4.4.0",
    "lodash.uniq": "^4.5.0",
    "lru-cache": "^5.1.1",
    "nightwatch": "^0.9.16",
    "nightwatch-helpers": "^1.2.0",
    "phantomjs-prebuilt": "^2.1.14",
    "puppeteer": "^1.11.0",
    "resolve": "^1.3.3",
    "rollup": "^1.0.0",
    "rollup-plugin-alias": "^1.3.1",
    "rollup-plugin-buble": "^0.19.6",
    "rollup-plugin-commonjs": "^9.2.0",
    "rollup-plugin-flow-no-whitespace": "^1.0.0",
    "rollup-plugin-node-resolve": "^4.0.0",
    "rollup-plugin-replace": "^2.0.0",
    "selenium-server": "^2.53.1",
    "serialize-javascript": "^3.1.0",
    "shelljs": "^0.8.1",
    "terser": "^3.10.2",
    "typescript": "^3.6.4",
    "webpack": "~4.28.4",
    "weex-js-runtime": "^0.23.6",
    "weex-styler": "^0.3.0",
    "yorkie": "^2.0.0"
  },
  "config": {
    "commitizen": {
      "path": "./node_modules/cz-conventional-changelog"
    }
  }
}

可以看到vue是采用rollup进行打包的，为了之后方便调试，需要加上sourceMap文件，我们将dev的脚本改动如下

{
    "scripts": {
        "dev": "rollup -w -c scripts/config.js --sourcemap --environment TARGET:web-full-dev"
    }
}

找到vue的入口文件

从脚本上可以看到scripts/config.js是项目的配置文件，我们来看下这个配置文件，代码量特别大，我们现在只关心入口文件是那个，所以找到核心代码。通过脚本dev可以得知，我们现在打包的是web-full-dev版本的文件。所以我们在配置文件中找到对应的入口文件。

'web-full-dev': {
    entry: resolve('web/entry-runtime-with-compiler.js'),
    dest: resolve('dist/vue.js'),
    format: 'umd',
    env: 'development',
    alias: { he: './entity-decoder' },
    banner
},

可以知道web/entry-runtime-with-compiler.js文件就是我们在调试vue源码时的入口文件。

现在我们来看下入口文件都做了哪些操作。

/* @flow */

import config from "core/config";
import { warn, cached } from "core/util/index";
import { mark, measure } from "core/util/perf";

import Vue from "./runtime/index";
import { query } from "./util/index";
import { compileToFunctions } from "./compiler/index";
import {
  shouldDecodeNewlines,
  shouldDecodeNewlinesForHref,
} from "./util/compat";

// 查找id选择器的dom节点，并返回其innerHTML.
const idToTemplate = cached((id) => {
  const el = query(id);
  return el && el.innerHTML;
});

const mount = Vue.prototype.$mount;
Vue.prototype.$mount = function (
  el?: string | Element,
  hydrating?: boolean
): Component {
  // query方法判断el是字符串还是dom节点，如果是字符串则通过document.querySelector转化成dom节点，如果是dom节点直接返回
  el = el && query(el);

  /* istanbul ignore if */
  // 如果el是body或者html则直接返回警告
  if (el === document.body || el === document.documentElement) {
    process.env.NODE_ENV !== "production" &&
      warn(
        `Do not mount Vue to <html> or <body> - mount to normal elements instead.`
      );
    return this;
  }

  const options = this.$options;
  // resolve template/el and convert to render function
  // 判断是否传入render方法，如果没有则将template转化成render方法
  if (!options.render) {
    let template = options.template;
    if (template) {
      if (typeof template === "string") {
        if (template.charAt(0) === "#") {
          template = idToTemplate(template);
          /* istanbul ignore if */
          if (process.env.NODE_ENV !== "production" && !template) {
            warn(
              `Template element not found or is empty: ${options.template}`,
              this
            );
          }
        }
      } else if (template.nodeType) {
        template = template.innerHTML;
      } else {
        if (process.env.NODE_ENV !== "production") {
          warn("invalid template option:" + template, this);
        }
        return this;
      }
    } else if (el) {
      template = getOuterHTML(el);
    }
    if (template) {
      /* istanbul ignore if */
      if (process.env.NODE_ENV !== "production" && config.performance && mark) {
        mark("compile");
      }
      // 根据template生成render函数，并挂载到options对象上
      const { render, staticRenderFns } = compileToFunctions(
        template,
        {
          outputSourceRange: process.env.NODE_ENV !== "production",
          shouldDecodeNewlines,
          shouldDecodeNewlinesForHref,
          delimiters: options.delimiters,
          comments: options.comments,
        },
        this
      );
      options.render = render;
      options.staticRenderFns = staticRenderFns;

      /* istanbul ignore if */
      if (process.env.NODE_ENV !== "production" && config.performance && mark) {
        mark("compile end");
        measure(`vue ${this._name} compile`, "compile", "compile end");
      }
    }
  }

  // 调用之前原型上的mount方法
  return mount.call(this, el, hydrating);
};

/**
 * Get outerHTML of elements, taking care
 * of SVG elements in IE as well.
 */
function getOuterHTML(el: Element): string {
  if (el.outerHTML) {
    return el.outerHTML;
  } else {
    const container = document.createElement("div");
    container.appendChild(el.cloneNode(true));
    return container.innerHTML;
  }
}

Vue.compile = compileToFunctions;

export default Vue;

从代码上得知，入口文件主要是完成了mount函数的调用，在调用过程中先判断用户有无传入的render函数，如果没有则将template转化成render函数，并且挂载到options上。

Vue构造函数

在new Vue()的过程中到底发生了什么，让我们来看下vue的构造函数，代码位置在src/core/instance/index.js中。

import { initMixin } from './init'
import { stateMixin } from './state'
import { renderMixin } from './render'
import { eventsMixin } from './events'
import { lifecycleMixin } from './lifecycle'
import { warn } from '../util/index'

function Vue (options) {
  if (process.env.NODE_ENV !== 'production' &&
    !(this instanceof Vue)
  ) {
    warn('Vue is a constructor and should be called with the `new` keyword')
  }
  this._init(options)
}

initMixin(Vue)
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)

代码量不多 我们来看new Vue的过程中到底发生了些什么。

• 首先调用了this._init方法，我们稍后来看他的功能
• 下面调用了一堆mixin方法

经过调试可以看到_init方法是在initMixin时候将方法挂载到Vue实例上的

export function initMixin (Vue: Class<Component>) {
  // 定义_init方法，在new Vue的时候会调用
  Vue.prototype._init = function (options?: Object) {
    const vm: Component = this
    // a uid
    vm._uid = uid++

    let startTag, endTag
    /* istanbul ignore if */
    if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
      startTag = `vue-perf-start:${vm._uid}`
      endTag = `vue-perf-end:${vm._uid}`
      mark(startTag)
    }

    // a flag to avoid this being observed
    vm._isVue = true
    // merge options
    if (options && options._isComponent) {
      // optimize internal component instantiation
      // since dynamic options merging is pretty slow, and none of the
      // internal component options needs special treatment.
      initInternalComponent(vm, options)
    } else {
      vm.$options = mergeOptions(
        resolveConstructorOptions(vm.constructor),
        options || {},
        vm
      )
    }
    /* istanbul ignore else */
    if (process.env.NODE_ENV !== 'production') {
      initProxy(vm)
    } else {
      vm._renderProxy = vm
    }
    // expose real self
    vm._self = vm
    initLifecycle(vm)
    initEvents(vm)
    initRender(vm)
    callHook(vm, 'beforeCreate')
    initInjections(vm) // resolve injections before data/props
    initState(vm)
    initProvide(vm) // resolve provide after data/props
    callHook(vm, 'created')

    /* istanbul ignore if */
    if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
      vm._name = formatComponentName(vm, false)
      mark(endTag)
      measure(`vue ${vm._name} init`, startTag, endTag)
    }

    if (vm.$options.el) {
      vm.$mount(vm.$options.el)
    }
  }
}

可以看到代码中调用了一些函数，

initLifecycle(vm)
initEvents(vm)
initRender(vm)
callHook(vm, 'beforeCreate')
initInjections(vm) // resolve injections before data/props
initState(vm)
initProvide(vm) // resolve provide after data/props
callHook(vm, 'created')

通过函数我们可以看到在created生命周期之前调用了初始化事件、初始化render函数、调用beforeCreate生命周期钩子、舒适化inject、初始化数据、初始化provide等操作，下节我们将详细介绍各个函数的作用，这一章的准备工作以及入口文件已经介绍完成。