a.ts

import {NgModule} from '@angular/core'
import {ModuleB} from './b'

@Component({
  selector: 'component-a',
  template: `
    <component-b></component-b>
  `
})
export class ComponentA {}
 
 
@NgModule({
  imports: [ ModuleB ],
  declarations: [ ComponentA ]
})
export class ModuleA {}

b.ts

import {NgModule} from '@angular/core'

@Component({
  selector: 'component-b'
})
export class ComponentB {}

@NgModule({
  declarations: [ ComponentB ],
  exports: [ ComponentB ]
})
export class ModuleB {

}