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env.js（env的初始化以及服务的加载）

路径：addons\web\static\src\env.js

这个文件的作用就是初始化env，主要是加载所有的服务。如orm, title, dialog等。

1、env.js 的加载时机

前文我们讲过前端的启动函数，start.js,其中有这么两句，这里有两个函数makeEnv和startServices，都在同级目录的env.js里

    const env = makeEnv();await startServices(env);

2、 makeEnv()

export function makeEnv() {return {bus: new EventBus(),services: {},debug: odoo.debug,get isSmall() {throw new Error("UI service not initialized!");},};
}

从代码可以看出，env有4个属性：

1. bus： 全局数据总线
2. services：全局服务对象
3. debug： 是否debug模式
4. isSmall：判断手机端还是移动端

这里抛出一个异常是为了在后面会覆盖这个方法。

从中可以看出，env最重要的其实就两个对象，一个是全局数据总线，负责组件之间通信，另一个就是service。

3、startServices

启动所有在注册表中注册的服务，并且保证所有的依赖都得到满足。

首先获取所有在注册表中注册的服务serviceRegistry

初始化元数据SERVICES_METADATA， 主要是保存service中sync的内容，有什么作用还不清楚

主角开始上场： startServices

启动所有在注册表中注册的服务，并且保证每个服务的依赖都得到满足。

    await Promise.resolve();     // 等待之前的异步操作都完成const toStart = new Set();   // 初始化要启动的服务，因为每个服务都不同，所以用了setserviceRegistry.addEventListener   // 这段没看懂，这里添加了一个事件监听，动态增加注册服务的await _startServices(env, toStart);  // 将env和toStart对象传入，干正事了

4._startServices(env, toStart)

4.1 填充 toStart 集合

    const services = env.services;   //获取了env中的service对象，这时候还是空的，啥也没有// 根据注册表中的服务信息，初始化了toStart集合，里面都是创建好的实例对象，并且有一个name属性。for (const [name, service] of serviceRegistry.getEntries()) {if (!(name in services)) {const namedService = Object.assign(Object.create(service), { name });toStart.add(namedService);}}

4.2、findNext()

关键的地方来了， 这里有一个关键的函数findNext()，先看看它的定义：

// 从toStart集合中遍历，有过集合中的服务有依赖并且依赖都已经满足了，则返回这个service，如果没有依赖，那么直接返回，找到第一个就返回，不叨叨，直到找不到，返回null   
function  {for (const s of toStart) {if (s.dependencies) {if (s.dependencies.every((d) => d in services)) {return s;}} else {return s;}}return null;}

4.3 、启动服务，并填充到env的services中

在start函数中，findNext函数返回的服务，第一步要最的就是从toStart 删除，这样遍历的次数会越来越少，我看过，odoo17一共有69个服务，while一共还要遍历69次，每次加载一个服务。 通过这种方式，很好的处理了服务之间的依赖关系，并且最大限度的实现了并行。

    // start as many services in parallel as possible 并行启动尽可能多的服务async function start() {let service = null;const proms = [];while ((service = findNext())) {const name = service.name;toStart.delete(service);     // 删除要加载的服务const entries = (service.dependencies || []).map((dep) => [dep, services[dep]]);const dependencies = Object.fromEntries(entries);let value;try {value = service.start(env, dependencies);     // 调用start函数,并将返回值付给value} catch (e) {value = e;console.error(e);}if ("async" in service) {SERVICES_METADATA[name] = service.async;     // 保存服务的元数据，后面可能会有用}if (value instanceof Promise) {                  // 如果value是一个Promiseproms.push(new Promise((resolve) => {value.then((val) => {services[name] = val || null;    // 将promise的返回值保存到services中}).catch((error) => {services[name] = error;console.error("Can't load service '" + name + "' because:", error);}).finally(resolve);}));} else {services[service.name] = value || null;  // 如果不是promise，直接将value保存到services中}}await Promise.all(proms);    // 等待所有的proms完成if (proms.length) {return start();           }}

到这里，前端js就完成了所有service的加载，要注意的是， env.services中保存的不是 services对象本身，而是service对象的start函数返回的对象。

这点很重要，每个service都要有start函数，而且要有返回值。

4.4、后面还有一段是异常处理

    if (toStart.size) {const names = [...toStart].map((s) => s.name);const missingDeps = new Set();[...toStart].forEach((s) =>s.dependencies.forEach((dep) => {if (!(dep in services) && !names.includes(dep)) {missingDeps.add(dep);}}));const depNames = [...missingDeps].join(", ");throw new Error(`Some services could not be started: ${names}. Missing dependencies: ${depNames}`);}

如果toStart.size >0 ,说明这里面的服务的依赖想没有得到满足，所以无法加载，会抛出一个Error

5、附录：odoo17 env.js

/** @odoo-module **/import { registry } from "./core/registry";import { EventBus } from "@odoo/owl";// -----------------------------------------------------------------------------
// Types
// -----------------------------------------------------------------------------/*** @typedef {Object} OdooEnv* @property {import("services").Services} services* @property {EventBus} bus* @property {string} debug* @property {(str: string) => string} _t* @property {boolean} [isSmall]*/// -----------------------------------------------------------------------------
// makeEnv
// -----------------------------------------------------------------------------/*** Return a value Odoo Env object** @returns {OdooEnv}*/
export function makeEnv() {return {bus: new EventBus(),services: {},debug: odoo.debug,get isSmall() {throw new Error("UI service not initialized!");},};
}// -----------------------------------------------------------------------------
// Service Launcher
// -----------------------------------------------------------------------------const serviceRegistry = registry.category("services");export const SERVICES_METADATA = {};
let startServicesPromise = null;/*** Start all services registered in the service registry, while making sure* each service dependencies are properly fulfilled.** @param {OdooEnv} env* @returns {Promise<void>}*/
export async function startServices(env) {// Wait for all synchronous code so that if new services that depend on// one another are added to the registry, they're all present before we// start them regardless of the order they're added to the registry.debuggerawait Promise.resolve();const toStart = new Set();serviceRegistry.addEventListener("UPDATE", async (ev) => {// Wait for all synchronous code so that if new services that depend on// one another are added to the registry, they're all present before we// start them regardless of the order they're added to the registry.await Promise.resolve();const { operation, key: name, value: service } = ev.detail;if (operation === "delete") {// We hardly see why it would be usefull to remove a service.// Furthermore we could encounter problems with dependencies.// Keep it simple!return;}if (toStart.size) {const namedService = Object.assign(Object.create(service), { name });toStart.add(namedService);} else {await _startServices(env, toStart);}});await _startServices(env, toStart);
}async function _startServices(env, toStart) {if (startServicesPromise) {return startServicesPromise.then(() => _startServices(env, toStart));}const services = env.services;for (const [name, service] of serviceRegistry.getEntries()) {if (!(name in services)) {const namedService = Object.assign(Object.create(service), { name });toStart.add(namedService);}}// start as many services in parallel as possibleasync function start() {let service = null;const proms = [];while ((service = findNext())) {const name = service.name;toStart.delete(service);const entries = (service.dependencies || []).map((dep) => [dep, services[dep]]);const dependencies = Object.fromEntries(entries);let value;try {value = service.start(env, dependencies);} catch (e) {value = e;console.error(e);}if ("async" in service) {SERVICES_METADATA[name] = service.async;}if (value instanceof Promise) {proms.push(new Promise((resolve) => {value.then((val) => {services[name] = val || null;}).catch((error) => {services[name] = error;console.error("Can't load service '" + name + "' because:", error);}).finally(resolve);}));} else {services[service.name] = value || null;}}await Promise.all(proms);if (proms.length) {return start();}}startServicesPromise = start();await startServicesPromise;startServicesPromise = null;if (toStart.size) {const names = [...toStart].map((s) => s.name);const missingDeps = new Set();[...toStart].forEach((s) =>s.dependencies.forEach((dep) => {if (!(dep in services) && !names.includes(dep)) {missingDeps.add(dep);}}));const depNames = [...missingDeps].join(", ");throw new Error(`Some services could not be started: ${names}. Missing dependencies: ${depNames}`);}function findNext() {for (const s of toStart) {if (s.dependencies) {if (s.dependencies.every((d) => d in services)) {return s;}} else {return s;}}return null;}
}