對(duì)于使用聯(lián)邦模塊的項(xiàng)目會(huì)有兩個(gè)依賴，一個(gè)是遠(yuǎn)程模塊，一個(gè)是共享模塊。上一篇文章解釋了遠(yuǎn)程模塊的加載和安裝并初始化共享作用域。consumes則是共享模塊的解決方案，用于在運(yùn)行時(shí)加載并安裝依賴的共享模塊。

為什么叫consumes？我理解是因?yàn)楣蚕砟K的獲取是在__webpack_require__.I中完成的，而consumes只是使用__webpack_require__.S中的數(shù)據(jù)來安裝對(duì)應(yīng)模塊。所以consumes是在消費(fèi)__webpack_require__.S中的數(shù)據(jù)。

__webpack_require__S.default = {react: {version: {get() {}, ...}}}

以上信息并沒有在__webpack_require__.m上，所以當(dāng)前環(huán)境并不能使用共享作用域中的內(nèi)容

var versionLt = (a, b) => {// see webpack/lib/util/semver.js for original codea=parseVersion(a),b=parseVersion(b);for(var r=0;;){if(r>=a.length)return r<b.length&&"u"!=(typeof b[r])[0];var e=a[r],n=(typeof e)[0];if(r>=b.length)return"u"==n;var t=b[r],f=(typeof t)[0];if(n!=f)return"o"==n&&"n"==f||("s"==f||"u"==n);if("o"!=n&&"u"!=n&&e!=t)return e<t;r++} }var findSingletonVersionKey = (scope, key) => {var versions = scope[key];return Object.keys(versions).reduce((a, b) => {return !a || (!versions[a].loaded && versionLt(a, b)) ? b : a;}, 0); };var satisfy = (range, version) => {// see webpack/lib/util/semver.js for original codeif(0 in range){version=parseVersion(version);var e=range[0],r=e<0;r&&(e=-e-1);for(var n=0,i=1,a=!0;;i++,n++){var f,s,g=i<range.length?(typeof range[i])[0]:"";if(n>=version.length||"o"==(s=(typeof(f=version[n]))[0]))return!a||("u"==g?i>e&&!r:""==g!=r);if("u"==s){if(!a||"u"!=g)return!1}else if(a)if(g==s)if(i<=e){if(f!=range[i])return!1}else{if(r?f>range[i]:f<range[i])return!1;f!=range[i]&&(a=!1)}else if("s"!=g&&"n"!=g){if(r||i<=e)return!1;a=!1,i--}else{if(i<=e||s<g!=r)return!1;a=!1}else"s"!=g&&"n"!=g&&(a=!1,i--)}}var t=[],o=t.pop.bind(t);for(n=1;n<range.length;n++){var u=range[n];t.push(1==u?o()|o():2==u?o()&o():u?satisfy(u,version):!o())}return!!o(); }var getSingletonVersion = (scope, scopeName, key, requiredVersion) => {var version = findSingletonVersionKey(scope, key);if (!satisfy(requiredVersion, version)) typeof console !== "undefined" && console.warn && console.warn(getInvalidSingletonVersionMessage(scope, key, version, requiredVersion));return get(scope[key][version]); };var get = (entry) => {entry.loaded = 1;return entry.get() };// 給入?yún)⒑瘮?shù)注入依賴項(xiàng)共享作用域scope，封裝的是scope的獲取， // 因?yàn)閟cope可能在初始化中，也可能初始化完成 var init = (fn) => (function(scopeName, a, b, c) {var promise = __webpack_require__.I(scopeName);// 等待共享作用域初始化完成if (promise && promise.then) return promise.then(fn.bind(fn, scopeName, __webpack_require__.S[scopeName], a, b, c));return fn(scopeName, __webpack_require__.S[scopeName], a, b, c); });var loadSingletonVersionCheckFallback = /*#__PURE__*/ init((scopeName, scope, key, version, fallback) => {if(!scope || !__webpack_require__.o(scope, key)) return fallback();return getSingletonVersion(scope, scopeName, key, version); });var installedModules = {}; var moduleToHandlerMapping = {"webpack/sharing/consume/default/react/react?5e40": () => (loadSingletonVersionCheckFallback("default", "react", [1,17,0,2], () => (Promise.all([__webpack_require__.e("vendors-node_modules_react_index_js"), __webpack_require__.e("node_modules_object-assign_index_js")]).then(() => (() => (__webpack_require__(/*! react */ "../node_modules/react/index.js"))))))),"webpack/sharing/consume/default/react-dom/react-dom": () => (loadSingletonVersionCheckFallback("default", "react-dom", [1,17,0,2], () => (Promise.all([__webpack_require__.e("vendors-node_modules_react-dom_index_js"), __webpack_require__.e("webpack_sharing_consume_default_react_react")]).then(() => (() => (__webpack_require__(/*! react-dom */ "../node_modules/react-dom/index.js"))))))),"webpack/sharing/consume/default/react/react?7071": () => (loadSingletonVersionCheckFallback("default", "react", [4,17,0,2], () => (__webpack_require__.e("vendors-node_modules_react_index_js").then(() => (() => (__webpack_require__(/*! react */ "../node_modules/react/index.js"))))))) }; // no consumes in initial chunks var chunkMapping = {"src_bootstrap_js": ["webpack/sharing/consume/default/react/react?5e40","webpack/sharing/consume/default/react-dom/react-dom"],"webpack_sharing_consume_default_react_react": ["webpack/sharing/consume/default/react/react?7071"] }; __webpack_require__.f.consumes = (chunkId, promises) => {if(__webpack_require__.o(chunkMapping, chunkId)) {chunkMapping[chunkId].forEach((id) => {if(__webpack_require__.o(installedModules, id)) return promises.push(installedModules[id]);var onFactory = (factory) => {installedModules[id] = 0;__webpack_require__.m[id] = (module) => {delete __webpack_require__.c[id];module.exports = factory();}};var onError = (error) => {delete installedModules[id];__webpack_require__.m[id] = (module) => {delete __webpack_require__.c[id];throw error;}};try {var promise = moduleToHandlerMapping[id]();if(promise.then) {promises.push(installedModules[id] = promise.then(onFactory)['catch'](onError));} else onFactory(promise);} catch(e) { onError(e); }});} }

chunkMapping中存著chunk對(duì)應(yīng)共享模塊的依賴，而moduleToHandlerMapping中存著共享模塊的獲取方式，通過方法__webpack_require__.f.consumes入?yún)⑦@兩個(gè)數(shù)據(jù)就能解析chunk依賴的模塊，并對(duì)模塊進(jìn)行安裝。

(loadSingletonVersionCheckFallback("default", "react", [1,17,0,2], fallback))

這一行表達(dá)的是在共享作用域default上尋找版本為1.17.0.2的react，如果找不到使用自帶的模塊fallback。

var init = (fn) => (function(scopeName, a, b, c) {var promise = __webpack_require__.I(scopeName);// 等待共享作用域初始化完成if (promise && promise.then) return promise.then(fn.bind(fn, scopeName, __webpack_require__.S[scopeName], a, b, c));return fn(scopeName, __webpack_require__.S[scopeName], a, b, c); });var loadSingletonVersionCheckFallback = /*#__PURE__*/ init((scopeName, scope, key, version, fallback) => {if(!scope || !__webpack_require__.o(scope, key)) return fallback();return getSingletonVersion(scope, scopeName, key, version); });

init方法用于初始化對(duì)應(yīng)共享作用域，共享作用域加載完成后將相關(guān)作用域信息作為入?yún)⒄{(diào)用init的入?yún)⒑瘮?shù)。

拿到作用域信息后調(diào)用方法getSingletonVersion(scope, scopeName, key, version)

getSingletonVersion

function getSingletonVersion(scope, scopeName, key, requiredVersion) {...return get(scope[key][version]); }var get = (entry) => {entry.loaded = 1;return entry.get(); };

get方法的返回值會(huì)作為方法onFactory的入?yún)?/p> var onFactory = (factory) => {installedModules[id] = 0;__webpack_require__.m[id] = (module) => {delete __webpack_require__.c[id];module.exports = factory();} };

onFactory執(zhí)行完成后__webpack_require__.m上就會(huì)出現(xiàn)對(duì)應(yīng)的模塊信息。到這里共享模塊也安裝完成了。

等待chunk src_bootstrap_js文件加載完成，外部依賴準(zhǔn)備完成，共享模塊準(zhǔn)備完成后chunk src_bootstrap_js 則表示加載完成可以開始執(zhí)行業(yè)務(wù)代碼了。

名字的翻譯

在源碼中使用的名字是 import React from ‘react’，而通過webpack編譯后變成了”webpack/sharing/consume/default/react/react?5e40”，并且在__webpack_require__.S上的名字也是react，這些是怎么關(guān)聯(lián)起來的呢？

該問題同樣存在于遠(yuǎn)程模塊加載場景中。

”webpack/sharing/consume/default/react/react?5e40”是怎么和共享作用域中的”react”關(guān)聯(lián)起來的？

在上面源碼中

var moduleToHandlerMapping = {"webpack/sharing/consume/default/react/react?5e40": () => (loadSingletonVersionCheckFallback("default", "react", [1,17,0,2], () => (Promise.all([__webpack_require__.e("vendors-node_modules_react_index_js"), __webpack_require__.e("node_modules_object-assign_index_js")]).then(() => (() => (__webpack_require__(/*! react */ "../node_modules/react/index.js"))))))), }

表示模塊"webpack/sharing/consume/default/react/react?5e40"需要在共享作用域default中的1.17.0.2版本的react，這里這兩個(gè)名字就關(guān)聯(lián)起來了。

源碼中的 import React from ‘react’ 是怎么和 "webpack/sharing/consume/default/react/react?5e40" 關(guān)聯(lián)起來的？

源碼中的

import React from 'react'

經(jīng)過編譯變成

var react__WEBPACK_IMPORTED_MODULE_0__ = __webpack_require__(/*! react */ "webpack/sharing/consume/default/react/react?5e40"); var react__WEBPACK_IMPORTED_MODULE_0___default = /*#__PURE__*/__webpack_require__.n(react__WEBPACK_IMPORTED_MODULE_0__);

這樣源碼中的名字 ”react”就和"webpack/sharing/consume/default/react/react?5e40"關(guān)聯(lián)起來了。

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