next.js/packages/next/src/build/templates/pages-edge-api.ts

import type { AdapterOptions } from '../../server/web/adapter'

import '../../server/web/globals'

import { adapter } from '../../server/web/adapter'
import { IncrementalCache } from '../../server/lib/incremental-cache'
import { wrapApiHandler } from '../../server/api-utils'

// Import the userland code.
import handler from 'VAR_USERLAND'

const page = 'VAR_DEFINITION_PAGE'

if (typeof handler !== 'function') {
  throw new Error(
    `The Edge Function "pages${page}" must export a \`default\` function`
  )
}

export default function (
  opts: Omit<AdapterOptions, 'IncrementalCache' | 'page' | 'handler'>
) {
  return adapter({
    ...opts,
    IncrementalCache,
    page: 'VAR_DEFINITION_PATHNAME',
    handler: wrapApiHandler(page, handler),
  })
}