sls invoke local won't work

[jrean]

Hey, I'm trying to understand the following behaviour. Here are the steps to reproduce:

// node v14.21.3
// npm 6.14.18

npm install serverless-webpack --save-dev

I update the package.json to include serverless version 3. Here is the default package.json:

{
  "name": "serverless-3",
  "version": "1.0.0",
  "description": "Serverless google-nodejs-typescript template",
  "main": "serverless.ts",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "deploy": "sls deploy",
    "compile": "tsc"
  },
  "engines": {
    "node": ">=14.15.0"
  },
  "devDependencies": {
    "@serverless/typescript": "^3.30.1",
    "@types/express": "^4.17.11",
    "@types/node": "^20.2.5",
    "express": "^4.18.2",
    "serverless": "^3.31.0",
    "serverless-google-cloudfunctions": "^4.6.0",
    "serverless-webpack": "^5.11.0",
    "ts-loader": "^9.4.3",
    "ts-node": "^10.9.1",
    "tsconfig-paths": "^4.2.0",
    "tsconfig-paths-webpack-plugin": "^4.0.1",
    "typescript": "^5.0.4",
    "webpack": "^5.84.1",
    "webpack-node-externals": "^3.0.0"
  },
  "author": "Corentin Doué",
  "license": "MIT"
}

I run the typescript compiler, no warnings / errors. All good. I run the default httpHello function locally with the following command: sls invoke local --function httpHello -p src/tests/mocks/postHelloWorld.json --verbose.
The content of postHelloWorld.json is as follow:

{
  "method": "POST",
  "headers": {
    "content-type": "application/json"
  },
  "body": {
    "message": "Hello World"
  }
}

All good it's very fast:

Running "serverless" from node_modules
Using configuration:
{
  "webpackConfig": "./webpack.config.js",
  "includeModules": true,
  "packager": "npm",
  "packagerOptions": {},
  "keepOutputDirectory": false,
  "concurrency": 4
}
Removing xxx/serverless-3/.webpack
[Webpack] Building with Webpack
...
 2023-05-28 16:33:27: webpack 5.84.1 compiled successfully in 306 ms (9c707081b43153503a0e)

{"severity":"INFO","message":"Hello World"}
{
    "status": 200,
    "headers": {}
}

Now, I update the default http-hello/handler.ts as follow, to have some validation layer:

import type { Request, Response } from './types';
import { body } from 'express-validator';
import { handleWithValidation } from '@libs/http-handler';
import { logger } from '@libs/logs';

export const httpHello = handleWithValidation(
  body('message').isString(),
  async (req: Request, res: Response) => {

    const {
      body: { message },
    } = req

    logger.info({ message })

    res.status(200).send()
  }
)

And the libs/http-handler.ts as follow:

import type { Request , Response, RequestHandler } from 'express';
import { validationResult as defaultValidationResult } from 'express-validator';
import express from 'express';
import { logger } from "@libs/logs";

export const handle = (...handlers: RequestHandler[]): RequestHandler => {
  const httpHandler = express()
  httpHandler.use(express.json())
  httpHandler.use(async (req: Request, res: Response, next): Promise<void> => {
    logger.init(req);

    try {
      next()
    } catch (error) {
      logger.error(error);
      res.status(500).send();
    }
  })

  httpHandler.use(handlers);

  return httpHandler;
};

export const validationResult = defaultValidationResult.withDefaults({
  formatter: error => {
    delete error.msg;
    return error;
  }
})

export const handleValidation: RequestHandler = (req, res, next) => {
  const errors = validationResult(req);

  if (!errors.isEmpty()) {
    return res.status(422).json({
      errors: errors.mapped()
    })
  }

  next()
}

export const handleWithValidation = (...handlers: RequestHandler[]): RequestHandler => {
  handlers.splice(handlers.length - 1, 0, handleValidation);

  return handle(...handlers);
}

Nothing crazy! I install the express-validator package. I run the typescript compiler, no warnings / errors.
I do not change anything from the previous tests.

I run the exact same command: sls invoke local --function httpHello -p src/tests/mocks/postHelloWorld.json --verbose.
But this time webpack stay stuck forever:

...
2023-05-28 16:41:41: webpack 5.84.1 compiled successfully in 329 ms (8958ac2868ea56396deb)
⠏ [Webpack] Building with Webpack ...

And the output of the function never happens.
What am I missing please?