neutrino-dev/packages/neutrino/src/neutrino.js

const path = require('path');
const EventEmitter = require('events').EventEmitter;
const DevServer = require('webpack-dev-server');
const webpack = require('webpack');
const Config = require('webpack-chain');
const ora = require('ora');

const cwd = process.cwd();

class Neutrino extends EventEmitter {
  constructor(presets = []) {
    super();
    this.config = new Config();
    this.custom = {};

    // Grab all presets and merge them into a single webpack-chain config instance
    presets.forEach(preset => {
      const paths = [
        path.join(cwd, preset),
        path.join(cwd, 'node_modules', preset),
        preset
      ];

      for (let i = 0; i < paths.length; i += 1) {
        let src;

        try {
          src = require(paths[i]);
        } catch (exception) {
          if (/Cannot find module/.test(exception.message)) {
            continue;
          }

          throw exception;
        }

        return src(this);
      }
    });

    // Also grab any Neutrino config from package.json and merge it into the config
    try {
      const pkg = require(path.join(process.cwd(), 'package.json'));

      if (pkg.config && pkg.config.neutrino) {
        this.config.merge(pkg.config.neutrino);
      }
    } catch (ex) {}
  }

  handleErrors(err, stats) {
    if (err) {
      console.error(err.stack || err);

      if (err.details) {
        console.error(err.details);
      }

      return true;
    }

    const jsonStats = stats.toJson();

    if (jsonStats.errors.length) {
      jsonStats.errors.map(err => console.error(err));
      return true;
    }

    return false;
  }

  getWebpackOptions() {
    if (this.__configCache) {
      return this.__configCache;
    }

    return this.__configCache = this.config.toConfig();
  }

  emitForAll(eventName, payload) {
    return Promise.all(this.listeners(eventName).map(fn => fn(payload)));
  }

  build(args) {
    return this
      .emitForAll('prebuild', args)
      .then(() => new Promise((resolve, reject) => {
        const config = this.getWebpackOptions();
        const compiler = webpack(config);

        compiler.run((err, stats) => {
          const failed = this.handleErrors(err, stats);

          if (failed) {
            return reject();
          }

          console.log(stats.toString({
            colors: true,
            chunks: false,
            children: false
          }));

          resolve();
        });
      }))
      .then(() => this.emitForAll('build', args));
  }

  start(args) {
    return this
      .emitForAll('prestart', args)
      .then(() => {
        const config = this.getWebpackOptions();

        if (config.devServer) {
          return this._devServer();
        }

        if (config.target === 'node') {
          console.log('Warning: This preset does not support watch compilation. Falling back to a one-time build.');
          return this.build();
        }

        return new Promise(resolve => {
          const config = this.getWebpackOptions();
          const compiler = webpack(config);
          const watcher = compiler.watch(config.watchOptions || {}, (err, stats) => {
            this.handleErrors(err, stats);
          });

          process.on('SIGINT', () => watcher.close(resolve));
        });
      })
      .then(() => this.emitForAll('start', args));
  }

  _devServer() {
    return new Promise(resolve => {
      const starting = ora('Starting development server').start();
      const config = this.getWebpackOptions();
      const protocol = config.devServer.https ? 'https' : 'http';
      const host = config.devServer.host || 'localhost';
      const port = config.devServer.port || 5000;

      config.devServer.noInfo = true;

      const compiler = webpack(config);
      const server = new DevServer(compiler, config.devServer);
      const building = ora('Waiting for initial build to finish').start();

      process.on('SIGINT', resolve);
      server.listen(port, host, () => {
        starting.succeed(`Development server running on: ${protocol}://${host}:${port}`);
        compiler.plugin('compile', () => {
          building.text = 'Source changed, re-compiling';
          building.start();
        });
        compiler.plugin('done', () => building.succeed('Build completed'));
      });
    });
  }

  test(args) {
    return this
      .emitForAll('pretest', args)
      .then(() => this.emitForAll('test', args));
  }
}

module.exports = Neutrino;