输入 rollup 配置

• 初始化计时器，构建完成时输出每个阶段的耗时、内存占用等信息,会 wrapper 相应 hook 方法，添加计时相关功能

initialiseTimers(inputOptions); 

根据用户配置开启插件性能分析

export function initialiseTimers(inputOptions: NormalizedInputOptions): void {if (inputOptions.perf) { // 开启插件性能分析timers = new Map();timeStart = timeStartImpl;timeEnd = timeEndImpl;inputOptions.plugins = inputOptions.plugins!.map(getPluginWithTimers);} else {timeStart = NOOP;timeEnd = NOOP;}
}

性能分析函数实现

• 通过 node 相关 Api 获取堆栈信息，process.memoryUsage()

let timers = new Map<string, Timer>();// 记录开始
function timeStartImpl(label: string, level = 3): void {label = getPersistedLabel(label, level);const startMemory = process.memoryUsage().heapUsed;const startTime = performance.now();const timer = timers.get(label);if (timer === undefined) { // 初始化创建对应标签timers.set(label, {memory: 0,startMemory,startTime,time: 0,totalMemory: 0});} else {timer.startMemory = startMemory;timer.startTime = startTime;}
}// 记录结束
function timeEndImpl(label: string, level = 3): void {label = getPersistedLabel(label, level);const timer = timers.get(label);if (timer !== undefined) {const currentMemory = process.memoryUsage().heapUsed;timer.memory += currentMemory - timer.startMemory;timer.time += performance.now() - timer.startTime;timer.totalMemory = Math.max(timer.totalMemory, currentMemory);}
}

分级输出结果

• 根据 level 控制台输出对应格式信息

function getPersistedLabel(label: string, level: number): string {switch (level) {case 1: {return `# ${label}`;}case 2: {return `## ${label}`;}case 3: {return label;}default: {return `${'  '.repeat(level - 4)}- ${label}`;}}
}

装饰器模式拓展组件

• 枚举需要性能分析的插件 hookName ，添加timeStart、timeEnd 分析功能

export function initialiseTimers(inputOptions: NormalizedInputOptions): void {if (inputOptions.perf) { // 是否开启性能分析timers = new Map();timeStart = timeStartImpl; // 记录开始timeEnd = timeEndImpl; // 记录结束inputOptions.plugins = inputOptions.plugins!.map(getPluginWithTimers);} else {timeStart = NOOP;timeEnd = NOOP;}
}

const TIMED_PLUGIN_HOOKS: readonly (keyof PluginHooks)[] = ['augmentChunkHash','buildEnd','buildStart','...','writeBundle'
];function getPluginWithTimers(plugin: any, index: number): Plugin {// 遍历需要分析的组件for (const hook of TIMED_PLUGIN_HOOKS) {if (hook in plugin) {let timerLabel = `plugin ${index}`;if (plugin.name) {timerLabel += ` (${plugin.name})`;}timerLabel += ` - ${hook}`; // 设置对应标签名// 在调用原插件方法前后增加性能分析const handler = function (this: any, ...parameters: readonly unknown[]) {timeStart(timerLabel, 4);const result = hookFunction.apply(this, parameters);timeEnd(timerLabel, 4);return result;};let hookFunction: any;// 格式化插件配置if (typeof plugin[hook].handler === 'function') {hookFunction = plugin[hook].handler;plugin[hook].handler = handler;} else {hookFunction = plugin[hook];plugin[hook] = handler;}}}return plugin;
}