細(xì)說(shuō)webpack源碼之compile流程-rules參數(shù)處理技巧(2)

if (rule.test || rule.include || rule.exclude) {
 // 標(biāo)記使用參數(shù)
 checkResourceSource("test + include + exclude");
 // 沒(méi)有就是undefined
 condition = {
 test: rule.test,
 include: rule.include,
 exclude: rule.exclude
 };
 // 處理常規(guī)參數(shù)
 try {
 newRule.resource = RuleSet.normalizeCondition(condition);
 } catch (error) {
 throw new Error(RuleSet.buildErrorMessage(condition, error));
 }
}

let resourceSource;
// ...
function checkResourceSource(newSource) {
 // 第一次直接跳到后面賦值
 if (resourceSource && resourceSource !== newSource)
 throw new Error(RuleSet.buildErrorMessage(rule, new Error("Rule can only have one resource source (provided " + newSource + " and " + resourceSource + ")")));
 resourceSource = newSource;
}

class RuleSet {
 constructor(rules) { /**/ };
 static normalizeCondition(condition) {
 // 假值報(bào)錯(cuò)
 if (!condition) throw new Error("Expected condition but got falsy value");
 // 檢測(cè)給定字符串是否以這個(gè)開(kāi)頭
 if (typeof condition === "string") { return str => str.indexOf(condition) === 0; }
 // 函數(shù)直接返回
 if (typeof condition === "function") { return condition; }
 // 正則表達(dá)式返回一個(gè)正則的test函數(shù)
 if (condition instanceof RegExp) { return condition.test.bind(condition); }
 // 數(shù)組map遞歸處理 有一個(gè)滿足返回true
 if (Array.isArray(condition)) {
  const items = condition.map(c => RuleSet.normalizeCondition(c));
  return orMatcher(items);
 }
 if (typeof condition !== "object") throw Error("Unexcepted " + typeof condition + " when condition was expected (" + condition + ")");
 const matchers = [];
 // 對(duì)象會(huì)對(duì)每個(gè)值進(jìn)行函數(shù)包裝彈入matchers中
 Object.keys(condition).forEach(key => {
  const value = condition[key];
  switch (key) {
  case "or":
  case "include":
  case "test":
   if (value)
   matchers.push(RuleSet.normalizeCondition(value));
   break;
  case "and":
   if (value) {
   const items = value.map(c => RuleSet.normalizeCondition(c));
   matchers.push(andMatcher(items));
   }
   break;
  case "not":
  case "exclude":
   if (value) {
   const matcher = RuleSet.normalizeCondition(value);
   matchers.push(notMatcher(matcher));
   }
   break;
  default:
   throw new Error("Unexcepted property " + key + " in condition");
  }
 });
 if (matchers.length === 0)
  throw new Error("Excepted condition but got " + condition);
 if (matchers.length === 1)
  return matchers[0];
 return andMatcher(matchers);
 }
}

class RuleSet {
 constructor(rules) { /**/ };
 /*
 Example:
 {
  test: /\.js$/,
  loader: 'babel-loader',
  include: [resolve('src'), resolve('test')]
 }
 */
 /*
 condition:
 {
  test: /\.js$/,
  include: ['d:\\workspace\\src', 'd:\\workspace\\test'],
  exclude: undefined
 }
 */
 static normalizeCondition(condition) {
 // include返回類(lèi)似于 [(str) => str.indexOf('d:\\workspace\\src') === 0,...] 的函數(shù)
 if (typeof condition === "string") { return str => str.indexOf(condition) === 0; }
 // test參數(shù)返回了 /\.js$/.test 函數(shù)
 if (condition instanceof RegExp) { return condition.test.bind(condition); }
 // include為數(shù)組
 if (Array.isArray(condition)) {
  const items = condition.map(c => RuleSet.normalizeCondition(c));
  return orMatcher(items);
 }
 const matchers = [];
 // 解析出['test','include','exclude']
 Object.keys(condition).forEach(key => {
  const value = condition[key];
  switch (key) {
  // 此value為一個(gè)數(shù)組
  case "include":
  case "test":
   if (value)
   matchers.push(RuleSet.normalizeCondition(value));
   break;
  // undefined跳過(guò)
  case "exclude":
   if (value) { /**/ }
   break;
  default:
   throw new Error("Unexcepted property " + key + " in condition");
  }
 });
 return andMatcher(matchers);
 }
}

function orMatcher(items) {
 // 當(dāng)一個(gè)函數(shù)被滿足條件時(shí)返回true
 return function(str) {
 for (let i = 0; i < items.length; i++) {
  if (items[i](str))
  return true;
 }
 return false;
 };
}

function andMatcher(items) {
 // 當(dāng)一個(gè)條件不滿足時(shí)返回false
 return function(str) {
 for (let i = 0; i < items.length; i++) {
  if (!items[i](str))
  return false;
 }
 return true;
 };
}

if (rule.resource) {
 // 如果前面檢測(cè)到了test || include || exclude參數(shù) 這里會(huì)報(bào)錯(cuò)
 checkResourceSource("resource");
 try {
 newRule.resource = RuleSet.normalizeCondition(rule.resource);
 } catch (error) {
 throw new Error(RuleSet.buildErrorMessage(rule.resource, error));
 }
}

/*
方式1:
 rules:[
 {
  test: /\.js$/,
  loader: 'babel-loader',
  include: [resolve('src'), resolve('test')]
 }
 ]
*/
/*
方式2:
 rules:[
 {
  resource:{
  test: /\.js$/,
  include: [resolve('src'), resolve('test')]
  exclude: undefined
  }
 }
 ]
*/

const loader = rule.loaders || rule.loader;
// 單loader情況
if (typeof loader === "string" && !rule.options && !rule.query) {
 checkUseSource("loader");
 newRule.use = RuleSet.normalizeUse(loader.split("!"), ident);
}
// loader配合options或query出現(xiàn)
else if (typeof loader === "string" && (rule.options || rule.query)) {
 checkUseSource("loader + options/query");
 newRule.use = RuleSet.normalizeUse({
 loader: loader,
 options: rule.options,
 query: rule.query
 }, ident);
}
// options與query同時(shí)出現(xiàn)報(bào)錯(cuò)
else if (loader && (rule.options || rule.query)) {
 throw new Error(RuleSet.buildErrorMessage(rule, new Error("options/query cannot be used with loaders (use options for each array item)")));
}
/*
 處理這種愚蠢用法時(shí)：
 {
 test: /\.css$/,
 loader: [{ loader: 'less-loader' }, { loader: 'css-loader' }]
 }
*/
else if (loader) {
 checkUseSource("loaders");
 newRule.use = RuleSet.normalizeUse(loader, ident);
}
// 單獨(dú)出現(xiàn)options或者query報(bào)錯(cuò)
else if (rule.options || rule.query) {
 throw new Error(RuleSet.buildErrorMessage(rule, new Error("options/query provided without loader (use loader + options)")));
}

static normalizeUse(use, ident) {
 // 單loader字符串
 if (Array.isArray(use)) {
 return use
  // 如果是單loader情況這里會(huì)返回[[loader1...],[loader2...]]
  .map((item, idx) => RuleSet.normalizeUse(item, `${ident}-${idx}`))
  // 扁平化后變成[loader1,loader2]
  .reduce((arr, items) => arr.concat(items), []);
 }
 // 對(duì)象或字符串
 return [RuleSet.normalizeUseItem(use, ident)];
};

// indet => 'ref-'
static normalizeUseItem(item, ident) {
 if (typeof item === "function")
 return item;
 if (typeof item === "string") {
 return RuleSet.normalizeUseItemString(item);
 }
 const newItem = {};
 if (item.options && item.query) throw new Error("Provided options and query in use");
 if (!item.loader) throw new Error("No loader specified");
 newItem.options = item.options || item.query;
 // 防止options:null的情況
 if (typeof newItem.options === "object" && newItem.options) {
 // 這里只是為了處理ident參數(shù)
 if (newItem.options.ident)
  newItem.ident = newItem.options.ident;
 else
  newItem.ident = ident;
 }
 // 取出loader參數(shù)
 const keys = Object.keys(item).filter(function(key) {
 return ["options", "query"].indexOf(key) < 0;
 });
 keys.forEach(function(key) {
 newItem[key] = item[key];
 });
 /*
 newItem = 
 {
 loader:'原字符串',
 ident:'ref-', (或自定義)
 options:{...}
 }
 */
 return newItem;
}

/*
Example:
{
 test: /\.css$/,
 loader: 'css-loader?{opt:1}!style-loader'
}

[{loader:'css-loader',options:{opt:1}},
{loader:'style-loader'}]
*/
static normalizeUseItemString(useItemString) {
 // 根據(jù)'?'切割獲取loader的參數(shù)
 const idx = useItemString.indexOf("?");
 if (idx >= 0) {
 return {
  loader: useItemString.substr(0, idx),
  // 后面的作為options返回
  options: useItemString.substr(idx + 1)
 };
 }
 return {
 loader: useItemString
 };
}

if (rule.use) {
 checkUseSource("use");
 newRule.use = RuleSet.normalizeUse(rule.use, ident);
}

/*
 {
 test:/\.css$/,
 user:['css-loader','style-loader]
 }
*/

/*
 {
 test:/\.css$/,
 user:{
  loader:'css-loader',
  options:'1'
 }
 }
*/

rules、oneOf
if (rule.rules)
 newRule.rules = RuleSet.normalizeRules(rule.rules, refs, `${ident}-rules`);
if (rule.oneOf)
 newRule.oneOf = RuleSet.normalizeRules(rule.oneOf, refs, `${ident}-oneOf`);

const keys = Object.keys(rule).filter((key) => {
 return ["resource", "resourceQuery", "compiler", "test", "include", "exclude", "issuer", "loader", "options", "query", "loaders", "use", "rules", "oneOf"].indexOf(key) < 0;
});
keys.forEach((key) => {
 newRule[key] = rule[key];
});

// 防止rules:[]的情況
if (Array.isArray(newRule.use)) {
 newRule.use.forEach((item) => {
 // ident來(lái)源于options/query的ident參數(shù)
 if (item.ident) {
  refs[item.ident] = item.options;
 }
 });
}