webpack插件分析

{
    main: {
      import: ['./index.js']
  }
}

EntryOptionPlugin.applyEntryOption里面

    static applyEntryOption(compiler, context, entry) {
        if (typeof entry === "function") {
            const DynamicEntryPlugin = require("./DynamicEntryPlugin");
            new DynamicEntryPlugin(context, entry).apply(compiler);
        } else {
            const EntryPlugin = require("./EntryPlugin");
            for (const name of Object.keys(entry)) {
                const desc = entry[name];
                const options = EntryOptionPlugin.entryDescriptionToOptions(
                    compiler,
                    name,
                    desc
                );
                for (const entry of desc.import) {
                    new EntryPlugin(context, entry, options).apply(compiler);
                }
            }
        }
    }

第15行，EntryPlugin的context参数是项目目录：/Users/didi/webpack-study
entry参数是字符串格式的入口文件地址：./src/index.js
EntryPlugin.apply：

    apply(compiler) {
        compiler.hooks.compilation.tap(
            "EntryPlugin",
            (compilation, { normalModuleFactory }) => {
                compilation.dependencyFactories.set(
                    EntryDependency,
                    normalModuleFactory
                );
            }
        );

        const { entry, options, context } = this;
        const dep = EntryPlugin.createDependency(entry, options);

        compiler.hooks.make.tapAsync("EntryPlugin", (compilation, callback) => {
            compilation.addEntry(context, dep, options, err => {
                callback(err);
            });
        });
    }

接下来重点看compiler.hooks.make的发布：

this.hooks.make.callAsync(compilation

这行执行时，上面EntryPlugin.apply订阅的方法（16-18行）就会执行：

            compilation.addEntry(context, dep, options, err => {
                callback(err);
            });

_addEntryItem中的name是’main’（下面代码的11行）

        if (entryData === undefined) {
            entryData = {
                dependencies: [],
                includeDependencies: [],
                options: {
                    name: undefined,
                    ...options
                }
            };
            entryData[target].push(entry);
            this.entries.set(name, entryData);