esbuild.config.mjs

#!/usr/bin/env node
// Requires esbuild 0.17+
//
// Esbuild is configured with 3 modes:
//
// `yarn build` - Build JavaScript and exit
// `yarn build --watch` - Rebuild JavaScript on change
// `yarn build --reload` - Reloads page when views, JavaScript, or stylesheets change
//
// Minify is enabled when "RAILS_ENV=production"
// Sourcemaps are enabled in non-production environments

import * as esbuild from "esbuild"
import path from "path"
import rails from "esbuild-rails"
import chokidar from "chokidar"
import http from "http"
import { setTimeout } from "timers/promises"

const clients = []
const entryPoints = [
    "application.js"
]
const watchDirectories = [
    "./app/javascript/**/*.js",
    "./app/views/**/*.html.erb",
    "./app/assets/builds/**/*.css", // Wait for cssbundling changes
]
const config = {
    absWorkingDir: path.join(process.cwd(), "app/javascript"),
    bundle: true,
    entryPoints: entryPoints,
    minify: process.env.RAILS_ENV == "production",
    outdir: path.join(process.cwd(), "app/assets/builds"),
    plugins: [rails()],
    sourcemap: process.env.RAILS_ENV != "production"
}

async function buildAndReload() {
    // Foreman & Overmind assign a separate PORT for each process
    const port = parseInt(process.env.PORT)
    const context = await esbuild.context({
        ...config,
        banner: {
            js: ` (() => new EventSource("http://localhost:${port}").onmessage = () => location.reload())();`,
        }
    })

    // Reload uses an HTTP server as an even stream to reload the browser
    http
        .createServer((req, res) => {
            return clients.push(
                res.writeHead(200, {
                    "Content-Type": "text/event-stream",
                    "Cache-Control": "no-cache",
                    "Access-Control-Allow-Origin": "*",
                    Connection: "keep-alive",
                })
            )
        })
        .listen(port)

    await context.rebuild()
    console.log("[reload] initial build succeeded")

    let ready = false
    chokidar
        .watch(watchDirectories)
        .on("ready", () => {
            console.log("[reload] ready")
            ready = true
        })
        .on("all", async (event, path) => {
            if (ready === false)  return

            if (path.includes("javascript")) {
                try {
                    await setTimeout(20)
                    await context.rebuild()
                    console.log("[reload] build succeeded")
                } catch (error) {
                    console.error("[reload] build failed", error)
                }
            }
            clients.forEach((res) => res.write("data: update\n\n"))
            clients.length = 0
        })
}

if (process.argv.includes("--reload")) {
    buildAndReload()
} else if (process.argv.includes("--watch")) {
    let context = await esbuild.context({...config, logLevel: 'info'})
    context.watch()
} else {
    esbuild.build(config)
}