next-dev.js

import { NextRequest } from 'https://esm.sh/v91/next@12.2.5/deno/dist/server/web/spec-extension/request.js'
import { NextResponse } from 'https://esm.sh/v91/next@12.2.5/deno/dist/server/web/spec-extension/response.js'
import { fromFileUrl } from 'https://deno.land/std@0.151.0/path/mod.ts'
import { buildResponse } from '../edge-shared/utils.ts'

globalThis.NFRequestContextMap ||= new Map()
globalThis.__dirname = fromFileUrl(new URL('./', import.meta.url)).slice(0, -1)
globalThis.process ||= { env: Deno.env.toObject() }

// Next.js uses this extension to the Headers API implemented by Cloudflare workerd
if (!('getAll' in Headers.prototype)) {
  Headers.prototype.getAll = function getAll(name) {
    name = name.toLowerCase()
    if (name !== 'set-cookie') {
      throw new Error('Headers.getAll is only supported for Set-Cookie')
    }
    return [...this.entries()].filter(([key]) => key === name).map(([, value]) => value)
  }
}

let idx = 0

const handler = async (req, context) => {
  if (!Deno.env.get('NETLIFY_DEV')) {
    // Only run in dev
    return
  }

  let middleware
  // Dynamic imports and FS operations aren't allowed when deployed,
  // but that's fine because this is only ever used locally.
  // We don't want to just try importing and use that to test,
  // because that would also throw if there's an error in the middleware,
  // which we would want to surface not ignore.
  try {
    // We need to cache-bust the import because otherwise it will claim it
    // doesn't exist if the user creates it after the server starts
    const nextMiddleware = await import(`../../middleware.js#${++idx}`)
    middleware = nextMiddleware.middleware
  } catch (importError) {
    if (importError.code === 'ERR_MODULE_NOT_FOUND' && importError.message.includes(`middleware.js`)) {
      //  No middleware, so we silently return
      return
    }

    throw importError
  }

  //  This is the format expected by Next.js along with the timezone which we support.
  const geo = {
    country: context.geo.country?.code,
    region: context.geo.subdivision?.code,
    city: context.geo.city,
    latitude: context.geo.latitude?.toString(),
    longitude: context.geo.longitude?.toString(),
    timezone: context.geo.timezone,
  }

  // A default request id is fine locally
  const requestId = req.headers.get('x-nf-request-id') || 'request-id'

  globalThis.NFRequestContextMap.set(requestId, {
    request: req,
    context,
  })

  const request = {
    headers: Object.fromEntries(req.headers.entries()),
    geo,
    method: req.method,
    ip: context.ip,
    body: req.body || undefined,
  }

  const nextRequest = new NextRequest(req, request)

  try {
    const response = await middleware(nextRequest)
    return buildResponse({
      result: { response: response || NextResponse.next(), waitUntil: Promise.resolve() },
      request: req,
      context,
    })
  } catch (error) {
    console.error(error)
    return new Response(error.message, { status: 500 })
  } finally {
    if (requestId) {
      globalThis.NFRequestContextMap.delete(requestId)
    }
  }
}

export default handler