TypeScript compile error in @middy/core 5.2.4

[cm-rwakatsuki]

Describe the bug After updating @middy/core from 5.2.3 to 5.2.4, an error occurred in TypeScript compile (tsc).

To Reproduce How to reproduce the behaviour:

Sample code

• packages/server/src/lambda/handlers/api-gateway/rest-api/router.ts

import serverlessExpress from "@codegenie/serverless-express";
import middy from "@middy/core";
import express from "express";

const app = express();

export const handler = middy(serverlessExpress({ app }));

Thrown error

tsc --noEmit

src/lambda/handlers/api-gateway/rest-api/router.ts:11:30 - error TS2345: Argument of type 'Handler<any, any> & ConfigureResult<any, any>' is not assignable to parameter of type 'PluginObject | MiddyInputHandler<any, any, Context> | undefined'.
  Type 'Handler<any, any> & ConfigureResult<any, any>' is not assignable to type 'MiddyInputHandler<any, any, Context>'.
    Types of parameters 'callback' and 'opts' are incompatible.
      Type 'MiddyHandlerObject' is not assignable to type 'Callback<any>'.
        Type 'MiddyHandlerObject' provides no match for the signature '(error?: string | Error | null | undefined, result?: any): void'.

11 export const handler = middy(serverlessExpress({ app }));

Expected behaviour tsc can run without errors.

Environment (please complete the following information):

• Node.js: 20.9.0
• Middy: 5.2.4
• AWS SDK 2.1450.0

[lynxSven]

Is this merge here the issue? https://github.com/middyjs/middy/pull/1165 The removal of the callback? Have the same issue with https://github.com/DefinitelyTyped/DefinitelyTyped/blob/7bd4a02ba62ede50a6198bd5b10712ae1a2fe6c8/types/aws-lambda/handler.d.ts#L84 the aws-lambda handler. Still has a callback but it doesn't match the new schema

[willfarrell]

Thanks for reporting. Would someone like to put a PR together for this fix?

[sekhavati]

Same issue is reproducible with the following basic Lambda using TypeScript 5.3.3:

import { type Handler } from "aws-lambda";
import middy from "@middy/core";

const baseHandler: Handler = async (event) => {
  console.log("Hello world");
};

export const handler = middy(baseHandler); // <== error here as described in issue thread

[garysassano]

I could confirm that my issue https://github.com/middyjs/middy/issues/1182 is related to this.

After downgrading to @middy/core 5.2.3, TypeScript stopped throwing the error.

[cmcnicholas]

This is really frustrating, writing a proxy function just to massage the types between middy and aws lambda here means me updating a few hundred functions across our services.

https://github.com/middyjs/middy/pull/1165#issuecomment-1980921633

[phmasek]

Thanks for reporting. Would someone like to put a PR together for this fix?

@willfarrell, how would you like that PR to address and resolve this issue?

[lmammino]

I might have a possible solution in #1198. Is there any blessed soul willing to review it? :)