How to use only dependency injection container from Nest.js framework?

Question

Is it possible to use just DI and IoC functionality from the Nest.js framework? If it is, how to achieve that?

I tried to implement it in this way:

import { NestFactory } from "@nestjs/core";
import { Module, Injectable } from "@nestjs/common";

@Injectable()
class AppRepository {
  sayHi() {
    console.log("app repository");
    console.log("Hello");
  }
}

@Injectable()
class AppService {
  constructor(private appRepository: AppRepository) {}
  sayHi() {
    console.log("app service");
    this.appRepository.sayHi();
  }
}

@Module({
  imports: [],
  providers: [AppService, AppRepository]
})
class AppModule {
  constructor(private appService: AppService) {}
  sayHi() {
    console.log("app module");
    this.appService.sayHi();
  }
}

async function bootstrap() {
  const app = await NestFactory.createApplicationContext(AppModule);
  const module = app.get<AppModule>(AppModule);
  module.sayHi();
}

bootstrap();

But when I run the code I get:

app module
(node:70976) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'sayHi' of undefined
    at AppModule.sayHi (/Users/jakub/projects/nest-di-clean/build/main.js:47:25)
    at /Users/jakub/projects/nest-di-clean/build/main.js:60:16
    at Generator.next (<anonymous>)
    at fulfilled (/Users/jakub/projects/nest-di-clean/build/main.js:11:58)
    at process._tickCallback (internal/process/next_tick.js:68:7)
    at Function.Module.runMain (internal/modules/cjs/loader.js:834:11)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)

So I get instance of AppModule, but an instance of AppService isn't injected.

I would like to use it in a library I'm contributing to which doesn't need controllers and other server-side stuff.

Answer 1

I found a solution. I didn't create a new project with nest-cli but just created an empty npm project with TypeScript and added @nestjs/common and @nestjs/core as dependencies (I want to minimize dependencies). My mistake was in tsconfig.json file where I forgot to allow emitDecoratorMetadata. Here is my package.json and tsconfig.json file for those who would be interested:

package.json

{
  "name": "nest-di-clean",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "compile": "yarn tsc",
    "start": "node ./build/main.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@nestjs/common": "^6.11.5",
    "@nestjs/core": "^6.11.5",
    "reflect-metadata": "^0.1.13",
    "rxjs": "^6.5.4"
  },
  "devDependencies": {
    "@types/node": "^13.7.0",
    "typescript": "^3.7.5"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "target": "ES2015",                     
    "module": "commonjs",                   
    "outDir": "./build",                    
    "strict": true,                         
    "esModuleInterop": true,                
    "experimentalDecorators": true,         
    "emitDecoratorMetadata": true,          
    "forceConsistentCasingInFileNames": true
  }
}

The content of main.js file is all in my question.