yarnpnp.js

const https = require('https');
const fs = require('fs');
const path = require('path');

const getPluginUrl = plugin => `https://raw.githubusercontent.com/yarnpkg/berry/master/packages/plugin-${plugin}/bin/%40yarnpkg/plugin-${plugin}.js`;

const packageData = require('./package.json');

if (!packageData.packman) {
    console.error('You must provide the `pacman` field in your package.json file!');
    process.exit(0);
}

const REQUESTED_VERSION = require('./package.json').packman.split('@')[1];
const YARNRC_YML_PATH = path.join(__dirname, '.yarnrc.yml');
const PLUGIN_LIST = !fs.existsSync(YARNRC_YML_PATH) ? [] : fs.readFileSync(YARNRC_YML_PATH, 'utf-8')
    .split('\n')
    .filter(line => line.includes('.yarn/plugins/@yarnpkg/plugin-'))
    .map(line => line.match(/.*plugin-(.*?)\.cjs/)[1]);
const YARN_URL = /^[0,1]\..*$/.test(REQUESTED_VERSION) ?
    `https://github.com/yarnpkg/yarn/releases/download/v${REQUESTED_VERSION}/yarn-${REQUESTED_VERSION}.js` :
    `https://raw.githubusercontent.com/yarnpkg/berry/%40yarnpkg/cli/${REQUESTED_VERSION}/packages/yarnpkg-cli/bin/yarn.js`;
const YARN_DIR = path.join(__dirname, '.yarn');
const RELEASES_DIR = path.join(YARN_DIR, 'releases');
const PLUGIN_DIR = path.join(YARN_DIR, 'plugins');
const YARN_BINARY = path.join(RELEASES_DIR, `yarn-${REQUESTED_VERSION}.cjs`);

let stats;
try {
    stats = fs.statSync(RELEASES_DIR);
} catch (e) {
    // Only catch to avoid crash
    // It is valid to continue
}
const CURRENT_YARN_BINARYNAME = !stats ? null : fs.readdirSync(RELEASES_DIR)[0];
const CURRENT_VERSION = !stats ? null : path.basename(CURRENT_YARN_BINARYNAME).slice(0, -path.extname(CURRENT_YARN_BINARYNAME).length).replace('yarn-', '');

const launchBerry = () => {
    const args = [];
    for (const arg of process.argv) {
        if (arg.indexOf('--production') === 0 || arg.indexOf('--ignore-engines') === 0)
            continue;
        else if (arg.indexOf('--frozen-lockfile') === 0)
            args.push('--immutable');
        else
            args.push(arg);
    }
    process.argv = args;
    delete process.env.YARN_PRODUCTION;
    require(YARN_BINARY);
};

const downloadFile = async (filePath, url) => {
    return new Promise((resolve, reject) => {
        https.get(url, res => {
            if (res.statusCode === 301 || res.statusCode === 302) {
                downloadFile(filePath, res.headers.location).then(resolve).catch(reject);
            } else if (res.statusCode !== 200) {
                reject(`Error downloading ${url}, status: ${res.statusCode}`);
            } else {
                const file = fs.createWriteStream(filePath);
                res.pipe(file);
                file.on('finish', () => {
                    resolve();
                });
            }
        }).on('error', err => {
            console.error(err);
            fs.unlink(filePath);
            reject(err);
        });
    });
};

const promises = [];

if (CURRENT_VERSION !== REQUESTED_VERSION) {
    if (CURRENT_YARN_BINARYNAME) {
        fs.rmdirSync(RELEASES_DIR, { recursive: true });
        fs.rmdirSync(PLUGIN_DIR, { recursive: true });
    }

    fs.mkdirSync(RELEASES_DIR, { recursive: true });
    console.log('Downloading Yarn Berry...');
    promises.push(downloadFile(YARN_BINARY, YARN_URL));
}

for (const plugin of PLUGIN_LIST) {
    const pluginPath = path.join(PLUGIN_DIR, '@yarnpkg', `plugin-${plugin}.cjs`);
    if (!fs.existsSync(pluginPath)) {
        fs.mkdirSync(path.join(PLUGIN_DIR, '@yarnpkg'), { recursive: true });
        console.log(`Downloading Yarn plugin ${plugin}...`);
        promises.push(downloadFile(pluginPath, getPluginUrl(plugin)));
    }
}

if (PLUGIN_LIST.length === 0) {
    fs.rmdirSync(PLUGIN_DIR, { recursive: true });
} else {
    const entries = fs.readdirSync(path.join(PLUGIN_DIR, '@yarnpkg'));
    for (const entry of entries) {
        const pluginName = entry.replace(/plugin-(.*)\.cjs/, '$1');
        if (!PLUGIN_LIST.includes(pluginName))
            fs.unlinkSync(path.join(PLUGIN_DIR, '@yarnpkg', `plugin-${pluginName}.cjs`));
    }
}

(async () => {
    try {
        await Promise.all(promises);
        launchBerry();
    } catch (err) {
        console.error(err);
    }
})();