ng-packagr: ng-packagr does not export angular interfaces

Type of Issue

Either a bug or a feature request

[ ] Bug Report [X] Feature Request

Description

Im trying to export an interface to the package in order to can be imported somewhere else. Im doing this on the public_api.ts file and i get everything exported but the interface.

PUBLIC API

export { SearchbarLibModule } from './src/app/searchbar-lib/searchbar-lib.module';
export { SearchbarInterface, SearchbarInterfaceInitialState } from './src/app/store/searchbar.store';
export { searchbarReducer } from './src/app/store/searchbar.reducers';

Interface code

import { SearchOption, SearchOptionInitialState } from '../shared/searchbar/searchbar.model';
import { FilterOption, FilterOptionInitialState } from '../shared/dialog-modal/filter.model';

interface SearchbarInterface {
  searchInterface: SearchOption;
  filterInterface: FilterOption;
}

const SearchbarInterfaceInitialState: SearchbarInterface = {
  searchInterface: SearchOptionInitialState,
  filterInterface: FilterOptionInitialState
}

export { SearchbarInterface, SearchbarInterfaceInitialState };

How To Reproduce

Just try to add an interface export in the public api and you will check why is not importing.

Expected Behaviour

for bugs: please describe what behaviour or result you expected

for features: do you have a first draft or an idea how to implement?

Version Information

ng-packagr: 1.6.0 @angular/*: 1.3.0 typescript: 2.3.3 rxjs: 5.4.2 node: 8.9.3 npm/yarn: 5.0.0

Im using the https://github.com/angular-redux/store for handling redux in my project.