Simple Working example of issue in NestJS where built-in exceptions thrown in "npm linked" modules result in 500 errors in consuming app.
In this repo, ModuleB imports ModuleA.
In moduleB/src/app.module.ts, you can choose to use unlinked or linked import by commenting/uncommenting.
As a courtesy, link and unlink scripts are provided in project root.
Two run scripts for ModuleB npm run startLinked and npm run startUnlinked.
After starting ModuleB, sending a GET request to http://localhost:3000/say/badWord will result in a BadRequestException being thrown, which has an error code of 400.
It can be observed that Exceptions thrown in the unlinked version will result in the desired Error Code. In the linked version, it will result in a 500. Example output below:
[Nest] 4136 - 04/25/2020, 1:55:46 AM [NestFactory] Starting Nest application...
[Nest] 4136 - 04/25/2020, 1:55:46 AM [InstanceLoader] ModuleA dependencies initialized +17ms
[Nest] 4136 - 04/25/2020, 1:55:46 AM [InstanceLoader] AppModule dependencies initialized +1ms
[Nest] 4136 - 04/25/2020, 1:55:46 AM [RoutesResolver] AppController {}: +4ms
[Nest] 4136 - 04/25/2020, 1:55:46 AM [RouterExplorer] Mapped {, GET} route +3ms
[Nest] 4136 - 04/25/2020, 1:55:46 AM [RoutesResolver] ModuleAController {}: +0ms
[Nest] 4136 - 04/25/2020, 1:55:46 AM [RouterExplorer] Mapped {/say/:key, GET} route +2ms
[Nest] 4136 - 04/25/2020, 1:55:46 AM [NestApplication] Nest application successfully started +3ms
[Nest] 4136 - 04/25/2020, 1:56:00 AM [ExceptionsHandler] do not know bad word +13581ms
Error: do not know bad word
at ModuleAController.saySomething (/home/mdaum/NestJSNpmLinkBug/moduleA/dist/app.controller.js:19:19)
at /home/mdaum/NestJSNpmLinkBug/moduleB/node_modules/@nestjs/core/router/router-execution-context.js:37:29
at process._tickCallback (internal/process/next_tick.js:68:7)
It would appear this is being treated as a regular Error instead of an exception that should be giving the desired non-200 error code.