Nuxt/packages/cli/src/commands/dev.ts

import { resolve } from 'upath'
import chokidar from 'chokidar'
import debounce from 'debounce-promise'
import type { Nuxt } from '@nuxt/kit'
import { createServer, createLoadingHandler } from '../utils/server'
import { showBanner } from '../utils/banner'
import { requireModule } from '../utils/cjs'
import { error } from '../utils/log'
import { defineNuxtCommand } from './index'

export default defineNuxtCommand({
  meta: {
    name: 'dev',
    usage: 'nu dev [rootDir] [--clipboard] [--open, -o]',
    description: 'Run nuxt development server'
  },
  async invoke (args) {
    process.env.NODE_ENV = process.env.NODE_ENV || 'development'
    const server = createServer()
    const listener = await server.listen({
      clipboard: args.clipboard,
      open: args.open || args.o
    })

    const rootDir = resolve(args._[0] || '.')

    const { loadNuxt, buildNuxt } = requireModule('@nuxt/kit', rootDir) as typeof import('@nuxt/kit')

    let currentNuxt: Nuxt
    const load = async (isRestart: boolean) => {
      try {
        const message = `${isRestart ? 'Restarting' : 'Starting'} nuxt...`
        server.setApp(createLoadingHandler(message))
        if (isRestart) {
          console.log(message)
        }
        if (currentNuxt) {
          await currentNuxt.close()
        }
        const newNuxt = await loadNuxt({ rootDir, dev: true, ready: false })
        currentNuxt = newNuxt
        await currentNuxt.ready()
        await buildNuxt(currentNuxt)
        server.setApp(currentNuxt.server.app)
        if (isRestart && args.clear !== false) {
          showBanner()
          listener.showURL()
        }
      } catch (err) {
        error(`Cannot ${isRestart ? 'restart' : 'start'} nuxt: `, err)
        server.setApp(createLoadingHandler(
          'Error while loading nuxt. Please check console and fix errors.'
        ))
      }
    }

    // Watch for config changes
    // TODO: Watcher service, modules, and requireTree
    const dLoad = debounce(load, 250)
    const watcher = chokidar.watch([rootDir], { ignoreInitial: true, depth: 1 })
    watcher.on('all', (_event, file) => {
      if (file.includes('nuxt.config') || file.includes('modules') || file.includes('pages')) {
        dLoad(true)
      }
    })

    await load(false)
  }
})