http-error-handler : set custom test to return error instead of `statusCode`

[Benjamin Besse]

Is your feature request related to a problem? Please describe.

Others libraries return error with statusCode but their are not HTTP-Errors and return many internal details (example : objection.js with mySqlError)

Actually, it's not possible to change how the test is made to return the error or use custom field/test to go to fallback

Describe the solution you'd like

• Use directly method isHttpError from http-errors or set a custom function to test if our function is a corect http-error or not

import middy from '@middy/core'
import httpErrorHandler from '@middy/http-error-handler'
import createError from 'http-errors'
import { isHttpError } from 'http-errors'

const lambdaHandler = (event, context) => {
  throw new createError.UnprocessableEntity()
}
export const handler = middy()
    .use(httpErrorHandler({ 
        fallbackMessage : JSON.stringify({ message : 'Internal Server Error' }),
        test: (err) => isHttpError(err)
    }))
    .handler(lambdaHandler)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[will Farrell]

Sounds like it would best handled by a custom error handler or a middleware to modify the non-http errors into ones.

[Benjamin Besse]

Actually, I made this middleware to fix that :

import type { MiddlewareObj } from '@middy/core';

import errorHandler from '@middy/http-error-handler';
import { isHttpError } from 'http-errors';

/**
 * Use @middy/http-error-handler with default error message configured
 */
export const httpErrorMiddleware = (): MiddlewareObj<unknown> => {
    const errorMiddleware = errorHandler({ fallbackMessage : JSON.stringify({ message : 'Internal Server Error' }) });

    return {
        onError : (request) => {
            if (!isHttpError(request.error)) {
                // eslint-disable-next-line @typescript-eslint/no-explicit-any
                (request.error as any).expose = false;
            }

            return errorMiddleware.onError?.(request);
        },
    };
};