webpack/bin/webpack.js

#!/usr/bin/env node

/**
 * @param {string} command process to run
 * @param {string[]} args commandline arguments
 * @returns {Promise<void>} promise
 */
const runCommand = (command, args) => {
	const cp = require("child_process");
	return new Promise((resolve, reject) => {
		const executedCommand = cp.spawn(command, args, {
			stdio: "inherit",
			shell: true
		});

		executedCommand.on("error", error => {
			reject(error);
		});

		executedCommand.on("exit", code => {
			if (code === 0) {
				resolve();
			} else {
				reject();
			}
		});
	});
};

/**
 * @param {string} packageName name of the package
 * @returns {boolean} is the package installed?
 */
const isInstalled = packageName => {
	try {
		require.resolve(packageName);

		return true;
	} catch (err) {
		return false;
	}
};

/**
 * @typedef {Object} CliOption
 * @property {string} name display name
 * @property {string} package npm package name
 * @property {string} binName name of the executable file
 * @property {boolean} installed currently installed?
 * @property {string} url homepage
 */

/** @type {CliOption} */
const cli = {
	name: "webpack-cli",
	package: "webpack-cli",
	binName: "webpack-cli",
	installed: isInstalled("webpack-cli"),
	url: "https://github.com/webpack/webpack-cli"
};

if (!cli.installed) {
	const path = require("path");
	const fs = require("graceful-fs");
	const readLine = require("readline");

	const notify =
		"CLI for webpack must be installed.\n" + `  ${cli.name} (${cli.url})\n`;

	console.error(notify);

	const isYarn = fs.existsSync(path.resolve(process.cwd(), "yarn.lock"));

	const packageManager = isYarn ? "yarn" : "npm";
	const installOptions = [isYarn ? "add" : "install", "-D"];

	console.error(
		`We will use "${packageManager}" to install the CLI via "${packageManager} ${installOptions.join(
			" "
		)}".`
	);

	const question = `Do you want to install 'webpack-cli' (yes/no): `;

	const questionInterface = readLine.createInterface({
		input: process.stdin,
		output: process.stderr
	});

	// If we're not in terminal mode, readline won't execute the callback function below. Return here
	// so that we can set the exit code properly.
	if (!questionInterface.terminal) {
		console.error(
			"You need to install 'webpack-cli' to use webpack via CLI.\n" +
				"You can also install the CLI manually."
		);
		process.exit(1);
	}
	questionInterface.question(question, answer => {
		questionInterface.close();

		const normalizedAnswer = answer.toLowerCase().startsWith("y");

		if (!normalizedAnswer) {
			console.error(
				"You need to install 'webpack-cli' to use webpack via CLI.\n" +
					"You can also install the CLI manually."
			);
			process.exitCode = 1;

			return;
		}

		console.log(
			`Installing '${
				cli.package
			}' (running '${packageManager} ${installOptions.join(" ")} ${
				cli.package
			}')...`
		);

		runCommand(packageManager, installOptions.concat(cli.package))
			.then(() => {
				require(cli.package); //eslint-disable-line
			})
			.catch(error => {
				console.error(error);
				process.exitCode = 1;
			});
	});
} else {
	const path = require("path");
	const pkgPath = require.resolve(`${cli.package}/package.json`);
	// eslint-disable-next-line node/no-missing-require
	const pkg = require(pkgPath);
	// eslint-disable-next-line node/no-missing-require
	require(path.resolve(path.dirname(pkgPath), pkg.bin[cli.binName]));
}