@nuxtjs/router/lib/module.js

const { resolve } = require('path')
const { existsSync } = require('fs')
const consola = require('consola')

function routerModule (moduleOptions) {
  this.nuxt.hook('build:before', () => {
    const defaultOptions = {
      path: this.options.srcDir,
      fileName: 'router.js',
      keepDefaultRouter: false
    }

    const options = {
      ...{},
      ...defaultOptions,
      ...this.options.routerModule,
      ...moduleOptions
    }

    const routerFilePath = resolve(options.path, options.fileName)

    // Check if router file path is defined
    if (!existsSync(routerFilePath)) {
      return consola.warn(`No \`${options.fileName}\` file found in \`${options.path}\`.`)
    }

    // Add router file path as the main template for routing
    this.addTemplate({
      fileName: 'router.js',
      src: routerFilePath
    })

    // Disable parsing `pages/`
    if (!options.keepDefaultRouter) {
      this.nuxt.options.build.createRoutes = () => {
        return []
      }

      return
    }

    // Put default router as .nuxt/defaultRouter.js
    let defaultRouter

    try {
      defaultRouter = require.resolve('@nuxt/vue-app/template/router')
    } catch (err) {
      /* istanbul ignore next */
      defaultRouter = require.resolve('nuxt/lib/app/router')
    }

    this.addTemplate({
      fileName: 'defaultRouter.js',
      src: defaultRouter
    })
  })
}

module.exports = routerModule
module.exports.meta = require('../package.json')