NestJS-Spelunker

Description

This module does a bit of a dive through the provided module and reads through the dependency tree from the point of entry given. It will find what a module imports, provides, has controllers for, and exports and will recursively search through the dependency tree until all modules have been scanned. For providers if there is a custom provider, the Spelunker will do its best to determine if Nest is to use a value, a class/standard, or a factory, and if a factory, what value is to be injected.

Exploration Mode

Exploration Usage

Much like the SwaggerModule, the SpelunkerModule is not a module that you register within Nest's DI system, but rather use after the DI system has done all of the heavy lifting. Simple usage of the Spelunker could be like:

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  SpelunkerModule.explore(app);
  app.listen(3000);
}

The SpelunkerModule will not get in the way of application bootstrapping, and will still allow for the server to listen.

Exploration Sample Output

Currently, the SpelunkerModule only logs to the terminal, though this is temporary and will eventually be to a file so that everything can be stylized. For now, this is a sample of the output:

[
  {
    name: 'AppModule',
    imports: ['AnimalsModule'],
    providers: {},
    controllers: [],
    exports: [],
  },
  {
    name: 'AnimalsModule',
    imports: ['CatsModule', 'DogsModule', 'HamstersModule'],
    providers: {
      AnimalsService: {
        method: 'value',
      },
    },
    controllers: ['AnimalsController'],
    exports: ['DogsModule'],
  },
  {
    name: 'CatsModule',
    imports: [],
    providers: {
      CatsService: {
        method: 'standard',
      },
    },
    controllers: ['CatsController'],
    exports: [],
  },
  {
    name: 'DogsModule',
    imports: [],
    providers: {
      DogsService: {
        method: 'factory',
        injections: ['someString'],
      },
      someString: {
        method: 'value',
      },
    },
    controllers: ['DogsController'],
    exports: ['DogsService'],
  },
  {
    name: 'HamstersModule',
    imports: [],
    providers: {
      HamstersService: {
        method: 'standard',
      },
    },
    controllers: ['HamstersController'],
    exports: [],
  },
];

In this example, AppModule imports AnimalsModule, and AnimalsModule imports CatsModule, DogsModule, and HamstersModule and each of those has its own set of providers and controllers.

Debug Mode

Every now again again you may find yourself running into problems where Nest can't resolve a provider's dependencies. The SpelunkerModule has a debug method that's meant to help out with this kind of situation.

Debug Usage

Assume you have a DogsModule with the following information:

@Module({
  controller: [DogsController],
  exports: [DogsService],
  providers: [
    {
      provide: 'someString',
      useVal:ue: 'something',
    },
    {
      provide: DogsService,
      inject: ['someString'],
      useFactory: (someStringInjection: string) => {
        return new DogsService(someStringInjection),
      },
    }
  ]
})
export class DogsModule {}

Now the SpelunkerModule.debug() method can be used anywhere with the DogsModule to get the dependency tree of the DogsModule including what the controller depends on, what imports are made, and what providers exist and their token dependencies.

async function bootstrap() {
  const dogsDeps = await SpelunkerModule.debug(DogsModule);
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}

Because this method does not require the INestApplicationContext it can be used before the NestFactory allowing you to have insight into what is being seen as the injection values and what's needed for the module to run.

Debug Sample Output

The output of the debug() method is an array of metadata, imports, controllers, exports, and providers. The DogsModule from above would look like this:

[
  {
    name: 'DogsModule',
    imports: [],
    providers: [
      {
        name: 'someString',
        dependencies: [],
        type: 'value',
      },
      {
        name: 'DogsService',
        dependencies: ['someString'],
        type: 'factory',
      },
    ],
    controllers: [
      {
        name: 'DogsController',
        dependencies: ['DogsService'],
      },
    ],
    exports: [
      {
        name: 'DogsService',
        type: 'provider',
      },
    ],
  },
];

Caution

This package is in early development, and any bugs found or improvements that can be thought of would be amazingly helpful. You can log a bug here, and you can reach out to me on Discord at PerfectOrphan#6003.