TypeError: Cannot call a class as a function

[clayrisser]

Bug Report

NestJS does not correctly detect class when babel transforms class to function.

Current behavior

throws following error

TypeError: Cannot call a class as a function

Input Code

.baberc

{
  "presets": [
    [
      "@babel/preset-env",
      {
        "corejs": 3,
        "spec": true,
        "useBuiltIns": "usage",
        "targets": {
          "node": "12"
        }
      }
    ],
    "@babel/preset-typescript"
  ],
  "plugins": [
    "babel-plugin-transform-typescript-metadata",
    ["@babel/plugin-proposal-decorators", { "legacy": true }],
    ["@babel/plugin-proposal-class-properties", { "loose": true }],
    "@babel/plugin-proposal-optional-chaining",
    "@babel/plugin-transform-runtime"
  ]
}

import { Injectable, Inject, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';

@Injectable()
export default class SomeMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    console.log('some middleware');
    next();
  }
}

Expected behavior

Should log some middleware when api is called.

Possible Solution

Update isClass implementation to detect a class that was transformed to a function.

nest/packages/core/middleware/utils.ts

Line 62 in d6bc71d

export function isClass(middleware: any): middleware is Type<any> {

Environment

Nest version: X.Y.Z

 
For Tooling issues:
- Node version: v12.20.0
- Platform:  Debian Linux
- NestJS: 7.6.13

[jmcdo29]

Please provide a minimum reproduction

[clayrisser]

This is worth reading regarding this issue. Basically it's only checking if it's a native class. It's not checking if it's a conventional class.

https://stackoverflow.com/a/49510834

Here is an example of a regex that checks for a conventional class. If we're worried that checking for a conventional class will trigger a false positive, we could also use duck typing to check if the use() method exists.

https://github.com/bevry/typechecker/blob/master/source/index.ts#L5

[clayrisser]

Please provide a minimum reproduction

docker run --rm -p 27017:27017 mongo

npm install -g pnpm
git clone https://github.com/clayrisser/example-graphback-nestjs
cd example-graphback-nestjs
make start

curl localhost:3000

[clayrisser]

I created a pull request to fix this. #6587

[kamilmysliwiec]

Let's track this herehttps://github.com//pull/6587