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

import type { NextApiResponse } from '../../types'
import type { IncomingMessage, ServerResponse } from 'node:http'

import { sendError } from '../../server/api-utils'
import { RouteKind } from '../../server/route-kind'
import type { Span } from '../../server/lib/trace/tracer'
import { PagesAPIRouteModule } from '../../server/route-modules/pages-api/module.compiled'

import { hoist } from './helpers'

// Import the userland code.
import * as userland from 'VAR_USERLAND'
import { getTracer, SpanKind } from '../../server/lib/trace/tracer'
import { BaseServerSpan } from '../../server/lib/trace/constants'
import type { InstrumentationOnRequestError } from '../../server/instrumentation/types'

// Re-export the handler (should be the default export).
export default hoist(userland, 'default')

// Re-export config.
export const config = hoist(userland, 'config')

// Create and export the route module that will be consumed.
const routeModule = new PagesAPIRouteModule({
  definition: {
    kind: RouteKind.PAGES_API,
    page: 'VAR_DEFINITION_PAGE',
    pathname: 'VAR_DEFINITION_PATHNAME',
    // The following aren't used in production.
    bundlePath: '',
    filename: '',
  },
  userland,
  distDir: process.env.__NEXT_RELATIVE_DIST_DIR || '',
  relativeProjectDir: process.env.__NEXT_RELATIVE_PROJECT_DIR || '',
})

export async function handler(
  req: IncomingMessage,
  res: ServerResponse,
  ctx: {
    waitUntil?: (prom: Promise<void>) => void
  }
): Promise<void> {
  let srcPage = 'VAR_DEFINITION_PAGE'

  // turbopack doesn't normalize `/index` in the page name
  // so we need to to process dynamic routes properly
  // TODO: fix turbopack providing differing value from webpack
  if (process.env.TURBOPACK) {
    srcPage = srcPage.replace(/\/index$/, '') || '/'
  }

  const prepareResult = await routeModule.prepare(req, res, { srcPage })

  if (!prepareResult) {
    res.statusCode = 400
    res.end('Bad Request')
    ctx.waitUntil?.(Promise.resolve())
    return
  }

  const { query, params, prerenderManifest, routerServerContext } =
    prepareResult

  try {
    const method = req.method || 'GET'
    const tracer = getTracer()

    const activeSpan = tracer.getActiveScopeSpan()
    const onRequestError =
      routeModule.instrumentationOnRequestError.bind(routeModule)

    const invokeRouteModule = async (span?: Span) =>
      routeModule
        .render(req, res, {
          query: {
            ...query,
            ...params,
          },
          params,
          allowedRevalidateHeaderKeys: process.env
            .__NEXT_ALLOWED_REVALIDATE_HEADERS as any as string[],
          multiZoneDraftMode: Boolean(process.env.__NEXT_MULTI_ZONE_DRAFT_MODE),
          trustHostHeader: process.env
            .__NEXT_TRUST_HOST_HEADER as any as boolean,
          // TODO: get this from from runtime env so manifest
          // doesn't need to load
          previewProps: prerenderManifest.preview,
          propagateError: false,
          dev: routeModule.isDev,
          page: 'VAR_DEFINITION_PAGE',

          internalRevalidate: routerServerContext?.revalidate,

          onError: (...args: Parameters<InstrumentationOnRequestError>) =>
            onRequestError(req, ...args),
        })
        .finally(() => {
          if (!span) return

          span.setAttributes({
            'http.status_code': res.statusCode,
            'next.rsc': false,
          })

          const rootSpanAttributes = tracer.getRootSpanAttributes()
          // We were unable to get attributes, probably OTEL is not enabled
          if (!rootSpanAttributes) {
            return
          }

          if (
            rootSpanAttributes.get('next.span_type') !==
            BaseServerSpan.handleRequest
          ) {
            console.warn(
              `Unexpected root span type '${rootSpanAttributes.get(
                'next.span_type'
              )}'. Please report this Next.js issue https://github.com/vercel/next.js`
            )
            return
          }

          const route = rootSpanAttributes.get('next.route')
          if (route) {
            const name = `${method} ${route}`

            span.setAttributes({
              'next.route': route,
              'http.route': route,
              'next.span_name': name,
            })
            span.updateName(name)
          } else {
            span.updateName(`${method} ${req.url}`)
          }
        })

    // TODO: activeSpan code path is for when wrapped by
    // next-server can be removed when this is no longer used
    if (activeSpan) {
      await invokeRouteModule(activeSpan)
    } else {
      await tracer.withPropagatedContext(req.headers, () =>
        tracer.trace(
          BaseServerSpan.handleRequest,
          {
            spanName: `${method} ${req.url}`,
            kind: SpanKind.SERVER,
            attributes: {
              'http.method': method,
              'http.target': req.url,
            },
          },
          invokeRouteModule
        )
      )
    }
  } catch (err) {
    // we re-throw in dev to show the error overlay
    if (routeModule.isDev) {
      throw err
    }
    // this is technically an invariant as error handling
    // should be done inside of api-resolver onError
    sendError(res as NextApiResponse, 500, 'Internal Server Error')
  } finally {
    // We don't allow any waitUntil work in pages API routes currently
    // so if callback is present return with resolved promise since no
    // pending work
    ctx.waitUntil?.(Promise.resolve())
  }
}