Node Workers based Webpack StartServerPlugin

plugin.ts

import { Worker } from "worker_threads";

import type { Compiler, compilation, Plugin } from "webpack";

interface Options {
	name: string;
	require?: string[];
	keyboard?: boolean;
}

type Callback = () => void;
type Compilation = compilation.Compilation;

export class StartServerPlugin implements Plugin {
	private options: Options;

	private worker: Worker | null;

	private restartWorker: Callback | undefined;

	constructor(options: Options) {
		this.options = {
			// Only listen on keyboard in development, so the server doesn't hang forever
			keyboard: process.env.NODE_ENV === "development",
			...options,
		};

		this.worker = null;

		this.enableRestarting();
	}

	apply(compiler: Compiler) {
		const plugin = { name: "StartServerPlugin" };

		compiler.hooks.afterEmit.tapAsync(plugin, this.afterEmit);
	}

	private afterEmit = ({ assets }: Compilation, callback: Callback) => {
		if (this.worker) {
			this.worker.terminate();
		}

		this.startServer(assets, callback);
	};

	private enableRestarting() {
		if (this.options.keyboard) {
			process.stdin.setEncoding("utf8");

			process.stdin.on("data", (data: string) => {
				if (data.trim() === "rs" && this.restartWorker) {
					console.log("Restarting app...");
					this.restartWorker();
				}
			});
		}
	}

	private startServer(assets: Record<string, { existsAt: string }>, callback: Callback) {
		const { name } = this.options;

		const targetFile = assets[name].existsAt;

		if (!targetFile) {
			console.error(`Entry ${name} not found. Try one of: ${Object.keys(assets).join(" ")}`);
		}

		this.restartWorker = () => {
			if (this.worker) {
				this.worker.terminate();
			}

			this.spawnWorker(targetFile, callback);
		};

		this.restartWorker();
	}

	private spawnWorker(entrypoint: string, callback: Callback) {
		this.worker = new Worker(
			`
		  require('v8-compile-cache');
		  ${this.options.require ? this.options.require.join(";\n") : ""}
		  require('${entrypoint}');
		`,
			{
				eval: true,
			}
		);

		this.worker.on("online", callback);
	}
}