说明
玩转 webpack 学习笔记
分析 seal 阶段怎么生成文件
我们可以打开 my-project\node_modules\webpack\lib\Compilation.js
找到 seal 方法
/**
* @param {Callback} callback signals when the seal method is finishes
* @returns {void}
*/
seal(callback) {
this.hooks.seal.call();
while (
this.hooks.optimizeDependenciesBasic.call(this.modules) ||
this.hooks.optimizeDependencies.call(this.modules) ||
this.hooks.optimizeDependenciesAdvanced.call(this.modules)
) {
/* empty */
}
this.hooks.afterOptimizeDependencies.call(this.modules);
this.hooks.beforeChunks.call();
for (const preparedEntrypoint of this._preparedEntrypoints) {
const module = preparedEntrypoint.module;
const name = preparedEntrypoint.name;
const chunk = this.addChunk(name);
const entrypoint = new Entrypoint(name);
entrypoint.setRuntimeChunk(chunk);
entrypoint.addOrigin(null, name, preparedEntrypoint.request);
this.namedChunkGroups.set(name, entrypoint);
this.entrypoints.set(name, entrypoint);
this.chunkGroups.push(entrypoint);
GraphHelpers.connectChunkGroupAndChunk(entrypoint, chunk);
GraphHelpers.connectChunkAndModule(chunk, module);
chunk.entryModule = module;
chunk.name = name;
this.assignDepth(module);
}
buildChunkGraph(
this,
/** @type {Entrypoint[]} */ (this.chunkGroups.slice())
);
this.sortModules(this.modules);
this.hooks.afterChunks.call(this.chunks);
this.hooks.optimize.call();
while (
this.hooks.optimizeModulesBasic.call(this.modules) ||
this.hooks.optimizeModules.call(this.modules) ||
this.hooks.optimizeModulesAdvanced.call(this.modules)
) {
/* empty */
}
this.hooks.afterOptimizeModules.call(this.modules);
while (
this.hooks.optimizeChunksBasic.call(this.chunks, this.chunkGroups) ||
this.hooks.optimizeChunks.call(this.chunks, this.chunkGroups) ||
this.hooks.optimizeChunksAdvanced.call(this.chunks, this.chunkGroups)
) {
/* empty */
}
this.hooks.afterOptimizeChunks.call(this.chunks, this.chunkGroups);
this.hooks.optimizeTree.callAsync(this.chunks, this.modules, err => {
if (err) {
return callback(err);
}
this.hooks.afterOptimizeTree.call(this.chunks, this.modules);
while (
this.hooks.optimizeChunkModulesBasic.call(this.chunks, this.modules) ||
this.hooks.optimizeChunkModules.call(this.chunks, this.modules) ||
this.hooks.optimizeChunkModulesAdvanced.call(this.chunks, this.modules)
) {
/* empty */
}
this.hooks.afterOptimizeChunkModules.call(this.chunks, this.modules);
const shouldRecord = this.hooks.shouldRecord.call() !== false;
this.hooks.reviveModules.call(this.modules, this.records);
this.hooks.optimizeModuleOrder.call(this.modules);
this.hooks.advancedOptimizeModuleOrder.call(this.modules);
this.hooks.beforeModuleIds.call(this.modules);
this.hooks.moduleIds.call(this.modules);
this.applyModuleIds();
this.hooks.optimizeModuleIds.call(this.modules);
this.hooks.afterOptimizeModuleIds.call(this.modules);
this.sortItemsWithModuleIds();
this.hooks.reviveChunks.call(this.chunks, this.records);
this.hooks.optimizeChunkOrder.call(this.chunks);
this.hooks.beforeChunkIds.call(this.chunks);
this.applyChunkIds();
this.hooks.optimizeChunkIds.call(this.chunks);
this.hooks.afterOptimizeChunkIds.call(this.chunks);
this.sortItemsWithChunkIds();
if (shouldRecord) {
this.hooks.recordModules.call(this.modules, this.records);
this.hooks.recordChunks.call(this.chunks, this.records);
}
this.hooks.beforeHash.call();
this.createHash();
this.hooks.afterHash.call();
if (shouldRecord) {
this.hooks.recordHash.call(this.records);
}
this.hooks.beforeModuleAssets.call();
this.createModuleAssets();
if (this.hooks.shouldGenerateChunkAssets.call() !== false) {
this.hooks.beforeChunkAssets.call();
this.createChunkAssets();
}
this.hooks.additionalChunkAssets.call(this.chunks);
this.summarizeDependencies();
if (shouldRecord) {
this.hooks.record.call(this, this.records);
}
this.hooks.additionalAssets.callAsync(err => {
if (err) {
return callback(err);
}
this.hooks.optimizeChunkAssets.callAsync(this.chunks, err => {
if (err) {
return callback(err);
}
this.hooks.afterOptimizeChunkAssets.call(this.chunks);
this.hooks.optimizeAssets.callAsync(this.assets, err => {
if (err) {
return callback(err);
}
this.hooks.afterOptimizeAssets.call(this.assets);
if (this.hooks.needAdditionalSeal.call()) {
this.unseal();
return this.seal(callback);
}
return this.hooks.afterSeal.callAsync(callback);
});
});
});
});
}
从上面代码可以看到里面做了很多优化工作,另外就是创建 hash
然后进行内容的生成
createModuleAssets 方法
emitAsset 方法
最后 emit 到磁盘
my-project\node_modules\webpack\lib\Compiler.js
this.hooks.emit.callAsync(compilation, err => {
if (err) return callback(err);
outputPath = compilation.getPath(this.outputPath);
this.outputFileSystem.mkdirp(outputPath, emitFiles);
});