Circular dependency between modules in nestjs

Question

The official doc is not clear about how modules in nestjs work and I'm having a problem with a circular dependency. It seems like my module structure is messed up I would like to understand what is wrong with it. The error I'm getting reads:

Nest cannot create the module instance. Often, this is because of a circular dependency between modules. Use forwardRef() to avoid it. (Read more: https://docs.nestjs.com/fundamentals/circular-dependency) Scope [AppModule -> UsersModule -> CategoriesModule]

Here are the import parts of all the modules mentioned in the error message.

AppModule:

UsersModule,
SmsRegistrationModule,
AuthModule,
SubscriptionModule,
EmailModule,
EntriesModule,
CategoriesModule,
AwsModule,
SharedModule

UsersModule:

CategoriesModule

CategoriesModule:

AwsModule,
SharedModule,

The error raised when I added SharedModule to the CategoriesModule module. Seems like I'm missing something on how these modules communicate and thus can't resolve this error.

Your help would be much apprecicted.

EDIT:

SharedModule:

@Module({
  providers: [
    CacheService,
    CodeGenService,
    IsUniqueEmail,
    BasicFileService,
  ],
  imports: [
    CacheModule.registerAsync({
      imports: [ConfigModule],
      useClass: CacheConfigService,
    }),
    UsersModule,
    AwsModule,
  ],
  exports: [
    CacheService,
    CodeGenService,
    IsUniqueEmail,
    BasicFileService,
  ],
})
export class SharedModule {}

There isn't enough here to know why you might have a circular dependency. What does SharedModule have in terms of import modules? — Jay McDoniel
@JayMcDoniel I've just added info on SharedModule, please, have a look. — Albert

Jay McDoniel Jay McDoniel · Accepted Answer · 2020-07-17T17:38:10

Your SharedModule imports UserModule, so the import chain (or at least the one I'm going to follow here) is AppModule -> UsersModule -> CategoriesModule -> SharedModule -> UsersModule -> CategoriesMOdule -> SharedModule -> .... To get around this, either the SharedModule should not import the UsersModule, or you should forward reference the CategoriesModule from the UserModule, the UserModule from the SharedModule and the SharedModule from the CategoriesModule. This is my first time seeing a circular dependency a few modules deep, so I can't give the exact syntax of how to work with the forwardRef method.

Circular dependency between modules in nestjs

1 Answers