微信小程序转换器之 loader设计实现

// analyze.config.js
// 引入loader
const jsLoader = require('./lib/jsLoader')
const jsonLoader = require('./lib/jsonLoader')
const cssLoader = require('./lib/cssLoader')
const htmlLoader = require('./lib/htmlLoader')
const signLoader = require('./lib/signLoader')
const config = {
    entry: './',
    output: {
        name: 'dist',
        src: './'
    },
    module: [
        {
            test: /\.js$/,
            loader: [signLoader, jsLoader],
        },
        {
            test: /\.wxss$/,
            loader: [cssLoader],
            outputPath: (outputPath) => outputPath.replace('.wxss', '.acss')
        },
        {
            test: /\.wxml$/,
            loader: [htmlLoader],
            outputPath: (outputPath) => outputPath.replace('.wxml', '.axml')
        },
        {
            test: /\.json$/,
            loader: [jsonLoader],
        },
    ]
}
module.exports = config

// 前几篇中封装的js转换器
const JsParser = require('./JsParser')
function loader(source) {
    
    const jsParser = new JsParser()
    let ast = jsParser.parse(source)
    ast = jsParser.astConverter(ast)
    return jsParser.astToCode(ast)
}
module.exports = loader

// 重写Analyze函数中的analyzeFileToLoard文件分析部分
function Analyze(filePath, outputPath){
    if (fs.statSync(filePath).isDirectory()) {
        const files = fs.readdirSync(filePath)
        files.forEach(file => {
            const currentFilePath = filePath+'/'+file
            const currentOutputPath = outputPath+'/'+file
            if(fs.statSync(currentFilePath).isDirectory()) {
                fs.mkdirSync(currentOutputPath)
                Analyze(currentFilePath, currentOutputPath)
            } else analyzeFileToLoard(currentFilePath, currentOutputPath)
        })
    } else analyzeFileToLoard(filePath, outputPath)
}

function analyzeFileToLoard(inputPath, outputPath) {
    let source = readFile(inputPath) // 读取源码
    const loaders = config.module
    loaders.forEach(loader => { // 遍历配置文件，看是否有匹配文件的loader规则
        if (loader.test.test(inputPath)) {
            // 使用loader
            source = useLoader(source, loader.loader, outputPath)
            // 输出路径处理函数
            if (loader.outputPath) outputPath = loader.outputPath(outputPath)
        }
    })
    writeFile(outputAppPath(outputPath), source) // 将处理过后的源码写入文件
}

function useLoader(source, loaders = []) {
    // 执行loader存储列表
    const loaderList = []
    // 递归去筛选需要执行的loader
    function loaderFilter(loaders) {
        const [firstLoader, ...ortherLoader] = loaders
        if (loaders.length === 0) return
        // 执行pitch，并将剩余的loader传入作为参数
        if (firstLoader.pitch && firstLoader.pitch(ortherLoader)) return ortherLoader
        else {
            // 将可用loader加入待执行列表
            loaderList.push(firstLoader)
            // 剩余loader作为参数 递归调用
            loaderFilter(ortherLoader)
        }
    }
    // 大概，暂时用不到。。。
    const remainLoader = loaderFilter(loaders)
    // 同步loader逆序执行
    function runLoader(source, loaderList) {
        const loader = loaderList.pop()
        let newSource = loader(source)
        if (loaderList.length > 0) return runLoader(newSource, loaderList)
        else return newSource
    }
    source = runLoader(source, loaderList)
    return source
}

function loader(source) {
let sign = `/**
* @Author： LY
*/
`
    source = sign + source
    return source
}
module.exports = loader