next.js/packages/next/src/next-devtools/server/get-next-error-feedback-middleware.ts

import { eventErrorFeedback } from '../../telemetry/events/error-feedback'
import { middlewareResponse } from './middleware-response'
import type { ServerResponse, IncomingMessage } from 'http'
import type { Telemetry } from '../../telemetry/storage'

// Handles HTTP requests to /__nextjs_error_feedback endpoint for collecting user feedback on error messages
export function getNextErrorFeedbackMiddleware(telemetry: Telemetry) {
  return async function (
    req: IncomingMessage,
    res: ServerResponse,
    next: () => void
  ): Promise<void> {
    const { pathname, searchParams } = new URL(`http://n${req.url}`)

    if (pathname !== '/__nextjs_error_feedback') {
      return next()
    }

    try {
      const errorCode = searchParams.get('errorCode')
      const wasHelpful = searchParams.get('wasHelpful')

      if (!errorCode || !wasHelpful) {
        return middlewareResponse.badRequest(res)
      }

      await telemetry.record(
        eventErrorFeedback({
          errorCode,
          wasHelpful: wasHelpful === 'true',
        })
      )

      return middlewareResponse.noContent(res)
    } catch (error) {
      return middlewareResponse.internalServerError(res)
    }
  }
}