runBundle.js

const {exec} = require('child_process');
const lineReader = require('line-reader');

const BASE_BUNDLE = 'android/app/src/main/assets/index.android-plain.bundle';
const HOME_BUNDLE = 'android/app/src/main/assets/home.bundle';

function getCommand(entryFile = 'index.js', output = BASE_BUNDLE) {
    return `NODE_ENV=production react-native bundle --platform android --dev false --entry-file ${entryFile} --bundle-output ${output} --reset-cache 2>&1`
}


function runBundle({entry, output}) {
    return new Promise((resolve) => {
        exec(getCommand(entry, output), {cwd: __dirname, maxBuffer: 10 * 1024 * 1024}, (err, stdout, stderr) => {
            if (err) {
                //some err occurred
                console.error(err)
            } else {
                // the *entire* stdout and stderr (buffered)
                console.log(`stdout: ${stdout}`);
                console.log(`stderr: ${stderr}`);
            }
            resolve()
        })
    })
}

const fs = require('fs')

function readBundle(fileName) {
    let preCode = ''
    let initCode = []
    let modules = []
    const exists = fs.existsSync(fileName)
    console.log('exists', exists)
    return new Promise((resolve, reject) => {
        lineReader.eachLine(fileName, (line, last) => {
            // console.log('line', line)
            if (!line.startsWith('__d')) {
                if (line.startsWith('__r')) {
                    initCode.push(line);
                } else {
                    preCode += `${line}\n`;
                }
            } else {
                const moduleId = /__d\(.*\},(.*),.*/.exec(line)[1]
                modules.push({id: moduleId, code: line})
            }
            if (last) {
                resolve({
                        preCode,
                        modules,
                        initCode
                    }
                )
            }
        });

    })
}

function removeBaseCode(outputPath, base = BASE_BUNDLE) {
    return new Promise(async (resolve, reject) => {
        const outputBundle = await readBundle(outputPath)
        const baseBundle = await readBundle(base)
        const baseModuleIds = new Set(baseBundle.modules.map(mod => mod.id))
        const modId = outputBundle.initCode[1].replace('__r(', '').replace(');', '')
        let lastSlashIndex = outputPath.lastIndexOf('/')
        let newPath = outputPath.substr(0, lastSlashIndex) + '/' + `chunk-${modId}-plain.bundle`;
        let writeStream = fs.createWriteStream(newPath, {flags: 'w'});
        outputBundle.modules.forEach(value => {
            if (!baseModuleIds.has(value.id)) {
                writeStream.write(value.code + "\n")
            }
        })
        //commandLine '../../node_modules/hermes-engine/osx-bin/hermes', 'src/main/assets/async.js', '-emit-binary', '-out', 'src/main/assets/async.bundle'
        const bytecodeBundlePath = newPath.replace('-plain.bundle', '.bundle')
        exec(`node_modules/hermes-engine/osx-bin/hermes ${newPath} -emit-binary -out ${bytecodeBundlePath}`, () => {
            resolve()
        })
    })
}

function buildBaseBundle() {
    return runBundle({entry: 'index.js', output: BASE_BUNDLE})
}

function buildBundle({entry, output}) {
    return runBundle({entry, output}).then(() => removeBaseCode(output))
}

function generateByteCode() {
    return new Promise((resolve, reject) => {
        const out = BASE_BUNDLE.replace('-plain.bundle', '.bundle')
        console.log('out', out)
        exec(`node_modules/hermes-engine/osx-bin/hermes ${BASE_BUNDLE} -emit-binary -out ${out}`, {
            cwd: __dirname,
            maxBuffer: 10 * 1024 * 1024
        }, (err, stdout, stderr) => {
            console.log('stdout', stdout)
            console.log('err', err)
            resolve()
        })
    })
}

buildBaseBundle()
    .then(() => buildBundle({entry: 'pages/home/index.js', output: HOME_BUNDLE}))
    .then(() => generateByteCode())