webpack/bin/webpack.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

#!/usr/bin/env node

/**
 * @param {string} command process to run
 * @param {string[]} args command line 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
	});

	// In certain scenarios (e.g. when STDIN is not in terminal mode), the callback function will not be
	// executed. Setting the exit code here to ensure the script exits correctly in those cases. The callback
	// function is responsible for clearing the exit code if the user wishes to install webpack-cli.
	process.exitCode = 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."
			);

			return;
		}
		process.exitCode = 0;

		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]));
}