Web error handling concept

The next step would be transferring the error to the frontend.

For this, you need to walk down the DetailedError chain and search for frontend information.

Here is an example of how it could look like:

// Example in go
func sendErrorResponse(w http.ResponseWriter, err error) {
	errorCode := "ERROR_INTERNAL_SERVER_ERROR"
	errorMessage := "Internal server error"
	statusCode := http.StatusInternalServerError

	for {
		detailedError, ok := err.(&DetailedError)
		if !ok {
			break
		}
		
		hasFrontendInfo := false
		if detailedError.FrontendErrorCode {
			errorCode = detailedError.FrontendErrorCode
			hasFrontendInfo = true
		}
		if detailedError.FrontendErrorMessage {
			errorMessage = detailedError.FrontendErrorMessage
			hasFrontendInfo = true
		}
		if detailedError.FrontendStatusCode {
			statusCode = detailedError.FrontendStatusCode
			hasFrontendInfo = true
		}
		if hasFrontendInfo {
			// break here, because we want the most recent info
			break
		}
		
		e = detailedError.InnerError
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(statusCode)
	fmt.Fprintf(w, toJsonString(map[string]any{
		"errorCode": errorCode,
		"error": errorMessage,
	}))
}

Or when you prefer TS:

// Example in TS
function sendErrorResponse(res: Response, e: unknown) {
	let errorCode = "ERROR_INTERNAL_SERVER_ERROR"
	let errorMessage = "Internal server error"
	let statusCode = 500
	let curentError: unknown =  e
	
	while (e instanceof DetailedError) {
		let hasFrontendInfo = false
		if (detailedError.frontendErrorCode) {
			errorCode = detailedError.frontendErrorCode
			hasFrontendInfo = true
		}
		if (detailedError.frontendErrorMessage) {
			errorMessage = detailedError.frontendErrorMessage
			hasFrontendInfo = true
		}
		if (detailedError.frontendStatusCode) {
			statusCode = detailedError.frontendStatusCode
			hasFrontendInfo = true
		}
		if (hasFrontendInfo) {
			// break here, because we want the most recent info
			break
		}
	
		e = e.innerError
	}
	
	res.status(statusCode).json({
		"errorCode": errorCode,
		"error": errorMessage,
	});
}