webpack-dev-server.js

#!/usr/bin/env node
/* Based on webpack/bin/webpack.js */
/* eslint-disable no-console */

'use strict';

/**
 * @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;
  }
};

/**
 * @param {CliOption} cli options
 * @returns {void}
 */
const runCli = (cli) => {
  if (cli.preprocess) {
    cli.preprocess();
  }
  const path = require('path');
  const pkgPath = require.resolve(`${cli.package}/package.json`);
  // eslint-disable-next-line import/no-dynamic-require
  const pkg = require(pkgPath);
  // eslint-disable-next-line import/no-dynamic-require
  require(path.resolve(path.dirname(pkgPath), pkg.bin[cli.binName]));
};

/**
 * @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
 * @property {function} preprocess preprocessor
 */

/** @type {CliOption} */
const cli = {
  name: 'webpack-cli',
  package: 'webpack-cli',
  binName: 'webpack-cli',
  installed: isInstalled('webpack-cli'),
  url: 'https://github.com/webpack/webpack-cli',
  preprocess() {
    process.argv.splice(2, 0, 'serve');
  },
};

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);

  let packageManager;

  if (fs.existsSync(path.resolve(process.cwd(), 'yarn.lock'))) {
    packageManager = 'yarn';
  } else if (fs.existsSync(path.resolve(process.cwd(), 'pnpm-lock.yaml'))) {
    packageManager = 'pnpm';
  } else {
    packageManager = 'npm';
  }

  const installOptions = [packageManager === 'yarn' ? '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(() => {
        runCli(cli);
      })
      .catch((error) => {
        console.error(error);
        process.exitCode = 1;
      });
  });
} else {
  runCli(cli);
}