DiscoveryService's getProviders and getControllers fail when metadata key is not applied at least once

[germangorodnev]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

When using getProvider/getControllers with metadataKey parameter and there is no use of this metadata, i.e. decorator is not applied to any class, -- both methods fail due to wrappersByMetaKey being undefined.

Error:

TypeError: Cannot read properties of undefined (reading 'get')
    at DiscoverableMetaHostCollection.getProvidersByMetaKey (/home/projects/nestjs-typescript-starter-9qt4jp/node_modules/@nestjs/core/discovery/discoverable-meta-host-collection.js:46:34)
    at DiscoveryService.getProviders (/home/projects/nestjs-typescript-starter-9qt4jp/node_modules/@nestjs/core/discovery/discovery-service.js:42:98)
    at AppTestModule.onModuleInit (/home/projects/nestjs-typescript-starter-9qt4jp/dist/main.js:38:49)
    at callModuleInitHook (/home/projects/nestjs-typescript-starter-9qt4jp/node_modules/@nestjs/core/hooks/on-module-init.hook.js:51:35)
    at async NestApplication.callInitHook (/home/projects/nestjs-typescript-starter-9qt4jp/node_modules/@nestjs/core/nest-application-context.js:223:13)
    at async NestApplication.init (/home/projects/nestjs-typescript-starter-9qt4jp/node_modules/@nestjs/core/nest-application.js:100:9)
    at async bootstrap (/home/projects/nestjs-typescript-starter-9qt4jp/dist/main.js:55:5)

Not sure if this is intended, as they're supposed to behave like filters and could just return an empty array when there are no suitable providers/controllers.

Minimum reproduction code

https://stackblitz.com/edit/nestjs-discovery-service-issue?file=src%2Fmain.ts

Steps to reproduce

1. npm i
2. npm run start
3. See error in the terminal

Then bring back @DiscoverDecorator on controller and provider - it will work.

Expected behavior

These methods could return [] instead.

Package

• I don't know. Or some 3rd-party package
• @nestjs/common
• @nestjs/core
• @nestjs/microservices
• @nestjs/platform-express
• @nestjs/platform-fastify
• @nestjs/platform-socket.io
• @nestjs/platform-ws
• @nestjs/testing
• @nestjs/websockets
• Other (see below)

Other package

No response

NestJS version

10.2.0+

Packages versions

Node.js version

18.18.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[kamilmysliwiec]

Let's track this here #12519