webpack 主入口

1. 读取 options、判断是否为 multiCompiler
2. 判断是否为 watch 模式
3. createCompiler 创建出compiler对象

/**
 * @param {WebpackOptions} rawOptions options object
 * @returns {Compiler} a compiler
 */
const createCompiler = (rawOptions) => {
    // 1. 处理 options
    const options = getNormalizedWebpackOptions(rawOptions)
    // 2. 添加默认配置项
    applyWebpackOptionsBaseDefaults(options)
    const compiler = new Compiler(options.context)
    compiler.options = options
    new NodeEnvironmentPlugin({
        infrastructureLogging: options.infrastructureLogging,
    }).apply(compiler)
    if (Array.isArray(options.plugins)) {
        for (const plugin of options.plugins) {
            if (typeof plugin === 'function') {
                plugin.call(compiler, compiler)
            } else {
                plugin.apply(compiler)
            }
        }
    }
    applyWebpackOptionsDefaults(options)
    compiler.hooks.environment.call()
    compiler.hooks.afterEnvironment.call()
    new WebpackOptionsApply().process(options, compiler)
    compiler.hooks.initialize.call()
    return compiler
}

compiler