Vue.js编译功能的实现

打开package.json文件，可以看到编译的脚本为

   "build": "node scripts/build.js",

是通过node执行build.js实现的，他的核心是buildEntry方法

function buildEntry (config) {
  const output = config.output
  const { file, banner } = output
  const isProd = /(min|prod)\.js$/.test(file)
  return rollup.rollup(config)
    .then(bundle => bundle.generate(output))
    .then(async ({ output: [{ code }] }) => {
      if (isProd) {
        const {code: minifiedCode} =  await terser.minify(code, {
          toplevel: true,
          compress: {
            pure_funcs: ['makeMap'],
          },
          format: {
            ascii_only: true,
          }
        });
        const minified = (banner ? banner + '\n' : '') + minifiedCode
        return write(file, minified, true)
      } else {
        return write(file, code)
      }
    })
}

将读取到的config传给rollup执行，将生成的js产物通过node提供的fsAPI写入到dist目录下，再看看scripts/config.js中vue都配置了哪些编译方案

const builds = {
  // Runtime only (CommonJS). Used by bundlers e.g. Webpack & Browserify
  'runtime-cjs-dev': {
    entry: resolve('web/entry-runtime.ts'),
    dest: resolve('dist/vue.runtime.common.dev.js'),
    format: 'cjs',
    env: 'development',
    banner
  },
  'runtime-cjs-prod': {
    entry: resolve('web/entry-runtime.ts'),
    dest: resolve('dist/vue.runtime.common.prod.js'),
    format: 'cjs',
    env: 'production',
    banner
  },
  // Runtime+compiler CommonJS build (CommonJS)
  'full-cjs-dev': {
    entry: resolve('web/entry-runtime-with-compiler.ts'),
    dest: resolve('dist/vue.common.dev.js'),
    format: 'cjs',
    env: 'development',
    alias: { he: './entity-decoder' },
    banner
  },
  'full-cjs-prod': {
    entry: resolve('web/entry-runtime-with-compiler.ts'),
    dest: resolve('dist/vue.common.prod.js'),
    format: 'cjs',
    env: 'production',
    alias: { he: './entity-decoder' },
    banner
  },
  // Runtime only ES modules build (for bundlers)
  'runtime-esm': {
    entry: resolve('web/entry-runtime-esm.ts'),
    dest: resolve('dist/vue.runtime.esm.js'),
    format: 'es',
    banner
  },
  // Runtime+compiler ES modules build (for bundlers)
  'full-esm': {
    entry: resolve('web/entry-runtime-with-compiler-esm.ts'),
    dest: resolve('dist/vue.esm.js'),
    format: 'es',
    alias: { he: './entity-decoder' },
    banner
  },
  // Runtime+compiler ES modules build (for direct import in browser)
  'full-esm-browser-dev': {
    entry: resolve('web/entry-runtime-with-compiler-esm.ts'),
    dest: resolve('dist/vue.esm.browser.js'),
    format: 'es',
    transpile: false,
    env: 'development',
    alias: { he: './entity-decoder' },
    banner
  },
  // Runtime+compiler ES modules build (for direct import in browser)
  'full-esm-browser-prod': {
    entry: resolve('web/entry-runtime-with-compiler-esm.ts'),
    dest: resolve('dist/vue.esm.browser.min.js'),
    format: 'es',
    transpile: false,
    env: 'production',
    alias: { he: './entity-decoder' },
    banner
  },
  // runtime-only build (Browser)
  'runtime-dev': {
    entry: resolve('web/entry-runtime.ts'),
    dest: resolve('dist/vue.runtime.js'),
    format: 'umd',
    env: 'development',
    banner
  },
  // runtime-only production build (Browser)
  'runtime-prod': {
    entry: resolve('web/entry-runtime.ts'),
    dest: resolve('dist/vue.runtime.min.js'),
    format: 'umd',
    env: 'production',
    banner
  },
  // Runtime+compiler development build (Browser)
  'full-dev': {
    entry: resolve('web/entry-runtime-with-compiler.ts'),
    dest: resolve('dist/vue.js'),
    format: 'umd',
    env: 'development',
    alias: { he: './entity-decoder' },
    banner
  },
  // Runtime+compiler production build  (Browser)
  'full-prod': {
    entry: resolve('web/entry-runtime-with-compiler.ts'),
    dest: resolve('dist/vue.min.js'),
    format: 'umd',
    env: 'production',
    alias: { he: './entity-decoder' },
    banner
  },
  // Web compiler (CommonJS).
  compiler: {
    entry: resolve('web/entry-compiler.ts'),
    dest: resolve('packages/template-compiler/build.js'),
    format: 'cjs',
    external: Object.keys(
      require('../packages/template-compiler/package.json').dependencies
    )
  },
  // Web compiler (UMD for in-browser use).
  'compiler-browser': {
    entry: resolve('web/entry-compiler.ts'),
    dest: resolve('packages/template-compiler/browser.js'),
    format: 'umd',
    env: 'development',
    moduleName: 'VueTemplateCompiler',
    plugins: [node(), cjs()]
  },
  // Web server renderer (CommonJS).
  'server-renderer-dev': {
    entry: resolve('packages/server-renderer/src/index.ts'),
    dest: resolve('packages/server-renderer/build.dev.js'),
    format: 'cjs',
    env: 'development',
    external: [
      'stream',
      ...Object.keys(
        require('../packages/server-renderer/package.json').dependencies
      )
    ]
  },
  'server-renderer-prod': {
    entry: resolve('server/index.ts'),
    dest: resolve('packages/server-renderer/build.prod.js'),
    format: 'cjs',
    env: 'production',
    external: [
      'stream',
      ...Object.keys(
        require('../packages/server-renderer/package.json').dependencies
      )
    ]
  },
  'server-renderer-basic': {
    entry: resolve('server/index-basic.ts'),
    dest: resolve('packages/server-renderer/basic.js'),
    format: 'umd',
    env: 'development',
    moduleName: 'renderVueComponentToString',
    plugins: [node(), cjs()]
  },
  'server-renderer-webpack-server-plugin': {
    entry: resolve('server/webpack-plugin/server.ts'),
    dest: resolve('packages/server-renderer/server-plugin.js'),
    format: 'cjs',
    external: Object.keys(
      require('../packages/server-renderer/package.json').dependencies
    )
  },
  'server-renderer-webpack-client-plugin': {
    entry: resolve('server/webpack-plugin/client.ts'),
    dest: resolve('packages/server-renderer/client-plugin.js'),
    format: 'cjs',
    external: Object.keys(
      require('../packages/server-renderer/package.json').dependencies
    )
  },
  'compiler-sfc': {
    entry: resolve('packages/compiler-sfc/src/index.ts'),
    dest: resolve('packages/compiler-sfc/dist/compiler-sfc.js'),
    format: 'cjs',
    external: Object.keys(
      require('../packages/compiler-sfc/package.json').dependencies
    ),
    plugins: [
      node({ preferBuiltins: true }),
      cjs({
        ignore: [
          ...Object.keys(require(consolidatePath).devDependencies),
          'vm',
          'crypto',
          'react-dom/server',
          'teacup/lib/express',
          'arc-templates/dist/es5',
          'then-pug',
          'then-jade'
        ]
      })
    ]
  }
}

核心的几个entry都在src/platforms/web下的，分别提供生产环境、开发环境下的cjs、es、umd规范产物

• entry-runtime.ts

import Vue from './runtime/index'
import * as vca from 'v3'
import { extend } from 'shared/util'

extend(Vue, vca)

export default Vue

• entry-runtime-esm.ts

import Vue from './runtime/index'

export default Vue

export * from 'v3'

• runtime-with-compiler.ts

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'
import type { Component } from 'types/component'
import type { GlobalAPI } from 'types/global-api'

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 {
  el = el && query(el)

  /* istanbul ignore if */
  if (el === document.body || el === document.documentElement) {
    __DEV__ &&
      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
  if (!options.render) {
    let template = options.template
    if (template) {
      if (typeof template === 'string') {
        if (template.charAt(0) === '#') {
          template = idToTemplate(template)
          /* istanbul ignore if */
          if (__DEV__ && !template) {
            warn(
              `Template element not found or is empty: ${options.template}`,
              this
            )
          }
        }
      } else if (template.nodeType) {
        template = template.innerHTML
      } else {
        if (__DEV__) {
          warn('invalid template option:' + template, this)
        }
        return this
      }
    } else if (el) {
      // @ts-expect-error
      template = getOuterHTML(el)
    }
    if (template) {
      /* istanbul ignore if */
      if (__DEV__ && config.performance && mark) {
        mark('compile')
      }

      const { render, staticRenderFns } = compileToFunctions(
        template,
        {
          outputSourceRange: __DEV__,
          shouldDecodeNewlines,
          shouldDecodeNewlinesForHref,
          delimiters: options.delimiters,
          comments: options.comments
        },
        this
      )
      options.render = render
      options.staticRenderFns = staticRenderFns

      /* istanbul ignore if */
      if (__DEV__ && config.performance && mark) {
        mark('compile end')
        measure(`vue ${this._name} compile`, 'compile', 'compile end')
      }
    }
  }
  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 as GlobalAPI

从几个entry看，Vue的实现最终都指向了src/platforms/web/runtime/index.ts