I am unsure what is really to blame for this issue. I think it's Typescript, but it could be ng-packagr or Angular. It only started when I updated to Angular 9.
Here is the message I get on my production build...
WARNING: Conflicting namespaces: dist/web-apps-shared/esm2015/public_api.js re-exports 'ɵ0' from both dist/web-apps-shared/esm2015/lib/api-applications/reducers.js and dist/web-apps-shared/esm2015/lib/account-codes/reducers.js (will be ignored)
Here is one of the sources that is causing this...
export const selectTotalAccountCodes = createSelector(selectSharedAccountCodeState,
(state: SharedAccountCodeState) => state.totalItems);
The compiler for some reason takes the function parameter and assigns it to a const and then exports it like so...
const ɵ0 = (state) => state.totalItems;
export const selectTotalAccountCodes = createSelector(selectSharedAccountCodeState, ɵ0);
export { ɵ0 };
The question I have is, why does ɵ0 need to be exported? It is only used internally in this file. I am I missing something? Should worry about this? It doesn't seem to be causing an issue when consuming the library that is built with this code.
I've got the same warning while updating to Angular 9, looking on the web for some info/solutions I've also found this Angular issue page https://github.com/angular/angular/issues/33668 ( 11/2019 so 3 months ago ), where they say that is an Ivy's issue, something related to the "export * ".
This is strange since I need to publish to npm and build recommendation says to disable Ivy , so I've disabled it ( angularCompilerOptions.enableIvy false in tsconfig.lib.json ): instead, set enableIvy to true makes the warning disappear.
So I did this try, while keeping enableIvy set to false in tsconfig.lib.json, in the public-api.ts I've modified the "export * " replacing the "*" with all the exported objects, one by one: warning is gone, the library is working.
But I really don't know if this is a good fix or if it is better just to show the warnings..