docusaurus/lib/dev.js

const ora = require('ora');
const path = require('path');
const fs = require('fs-extra');
const chalk = require('chalk');
const webpack = require('webpack');
const chokidar = require('chokidar');
const serve = require('webpack-serve');
const load = require('./loader');
const createDevConfig = require('./webpack/dev');
const blogiLog = require('./webpack/log');

module.exports = async function dev(sourceDir, cliOptions = {}) {
  const logger = ora(chalk.blue('Starting development server')).start();

  // load site props from preprocessed files in source directory
  const props = await load(sourceDir);

  // Reload for any add/change/remove of file
  const reload = () => {
    load(sourceDir).catch(err => {
      console.error(chalk.red(err.stack));
    });
  };
  const fsWatcher = chokidar.watch(['**/*.md'], {
    cwd: sourceDir,
    ignoreInitial: true
  });
  fsWatcher.on('add', reload);
  fsWatcher.on('change', reload);
  fsWatcher.on('unlink', reload);
  fsWatcher.on('addDir', reload);
  fsWatcher.on('unlinkDir', reload);

  // resolve webpack config
  let config = createDevConfig(props);

  const port = cliOptions.port || 8080;
  const {publicPath} = props;

  config.plugin('blogi-log').use(blogiLog, [
    {
      port,
      publicPath
    }
  ]);

  // create compiler from generated webpack config
  config = config.toConfig();
  const compiler = webpack(config);
  logger.succeed();

  // webpack-serve
  await serve(
    {},
    {
      compiler,
      open: false, // don't open browser automatically
      devMiddleware: {
        logLevel: 'warn',
        publicPath
      },
      hotClient: {
        port: port + 1,
        logLevel: 'error'
      },
      logLevel: 'error',
      port
    }
  );
};