较新版本Cesium使用本地源码编译打包

0 写作背景

较新版本的Cesium（1.100版本及以后）在代码结构上做了一定的调整，打包方式也随之发生了一些变化。

Starting with version 1.100, CesiumJS will be published alongside two smaller packages @cesium/engine and @cesium/widgets

老版本修改了本地源码，执行 gulp build 即可编译出新的版本库；较新版本默认用 node_modules中从 npm 下载来的Cesium代码打包，因此对本地源码（packages/engine、packages/widgets）做的改动不会出现在打包结果中。

打开 Source/Cesium.js 文件，可以看到引用的是 node_modules 下文件的路径。在打包过程中，会根据这里的路径把所有代码合并到一个大文件中（Build/CesiumUnminified/index.js、Build/CesiumUnminified/Cesium.js 等）

export const VERSION = '1.119';
export { AutomaticUniforms } from '@cesium/engine';
export { Buffer } from '@cesium/engine';
export { BufferUsage } from '@cesium/engine';
export { ClearCommand } from '@cesium/engine';
export { ComputeCommand } from '@cesium/engine';
export { ComputeEngine } from '@cesium/engine';
export { Context } from '@cesium/engine';
export { ContextLimits } from '@cesium/engine';
export { createUniform } from '@cesium/engine';
...

打包使用的索引文件 Source/Cesium.js

1 解决方案

1.1）按如下代码片段修改 scripts/build.js 的 generateDeclaration 函数

function generateDeclaration(workspace, file) {let assignmentName = path.basename(file, path.extname(file));let moduleId = file;moduleId = filePathToModuleId(moduleId);if (moduleId.indexOf("Source/Shaders") > -1) {assignmentName = `_shaders${assignmentName}`;}assignmentName = assignmentName.replace(/(\.|-)/g, "_");// return `export { ${assignmentName} } from '@${scope}/${workspace}';`;// 用本地源码的路径return `export { default as ${assignmentName} } from '../${file}';`;
}

重新执行 gulp build 后，Source/Cesium.js 文件中引用的路径会变成本地路径：

export const VERSION = '1.119';
export { default as AutomaticUniforms } from '../packages/engine/Source/Renderer/AutomaticUniforms.js';
export { default as Buffer } from '../packages/engine/Source/Renderer/Buffer.js';
export { default as BufferUsage } from '../packages/engine/Source/Renderer/BufferUsage.js';
export { default as ClearCommand } from '../packages/engine/Source/Renderer/ClearCommand.js';
export { default as ColorTable } from '../packages/engine/Source/Renderer/ColorTable.js';
export { default as ComputeCommand } from '../packages/engine/Source/Renderer/ComputeCommand.js';
export { default as ComputeEngine } from '../packages/engine/Source/Renderer/ComputeEngine.js';
export { default as Context } from '../packages/engine/Source/Renderer/Context.js';
export { default as ContextLimits } from '../packages/engine/Source/Renderer/ContextLimits.js';
export { default as createUniform } from '../packages/engine/Source/Renderer/createUniform.js';
export { default as createUniformArray } from '../packages/engine/Source/Renderer/createUniformArray.js';
export { default as CubeMap } from '../packages/engine/Source/Renderer/CubeMap.js';
...

修改后的索引文件 Source/Cesium.js

1.2）改完这些还不算，本地源码 packages/widgets/Source 里也有一些地方引用了@cesium/engine。例如下面的形式：

import {Clock,defined,destroyObject,EventHelper,JulianDate,
} from "@cesium/engine";
import knockout from "./ThirdParty/knockout.js";

本地源码也引用了node_modules下的源码

我们可以很容易在IDE中通过正则表达式替换掉对 @cesium/engine 的引用

根目录下（./packages/widgets/Source/*.js）的替换为 ../../engine/index.js

二级目录下（./packages/widgets/Source/*/*.js）的替换为 ../../../engine/index.js

至此，打包使用的就完全是本地源码了！

2 gulp build 命令解读

打包命令 gulp build 干了什么？gulp build 对应下面的 build 函数

export async function build() {// ...await buildEngine(buildOptions);await buildWidgets(buildOptions);await buildCesium(buildOptions);
}

2.1）buildEngine：

glsl 文件编译成 js 文件;
把 engine 下所有js文件的导出列表写到 packages/engine/index.js 中
把 engine/Source 文件夹下所有 web worker 文件组织到 packages/engine/Build/Workers 文件夹下
自动化测试文件相关（此处不详细说明）

globalThis.CESIUM_VERSION = "1.119";
export { default as AutomaticUniforms } from './Source/Renderer/AutomaticUniforms.js';
export { default as Buffer } from './Source/Renderer/Buffer.js';
export { default as BufferUsage } from './Source/Renderer/BufferUsage.js';
export { default as ClearCommand } from './Source/Renderer/ClearCommand.js';
export { default as ComputeCommand } from './Source/Renderer/ComputeCommand.js';
export { default as ComputeEngine } from './Source/Renderer/ComputeEngine.js';
export { default as Context } from './Source/Renderer/Context.js';
export { default as ContextLimits } from './Source/Renderer/ContextLimits.js';
...

packages/engine/index.js

2.2）buildWidgets:

把 packages/widgets 下所有 js 文件的导出列表写到 packages/widgets/index.js 中
自动化测试文件相关（此处不详细说明）

globalThis.CESIUM_VERSION = "1.119";
export { default as ClockViewModel } from './Source/ClockViewModel.js';
export { default as Command } from './Source/Command.js';
export { default as createCommand } from './Source/createCommand.js';
export { default as InspectorShared } from './Source/InspectorShared.js';
export { default as subscribeAndEvaluate } from './Source/subscribeAndEvaluate.js';
export { default as SvgPathBindingHandler } from './Source/SvgPathBindingHandler.js';
export { default as ToggleButtonViewModel } from './Source/ToggleButtonViewModel.js';
export { default as Animation } from './Source/Animation/Animation.js';
export { default as AnimationViewModel } from './Source/Animation/AnimationViewModel.js';
...

packages/widgets/index.js

2.3）buildCesium：