I am trying to implement lazy loading in my Angular 6 app, all of my http calls are made in the FeatureModule (lazy loaded), but still I have to add HttpClientModule in my AppModule and not in FeatureModule. Didn't really understand why.
Also, when I added interceptors in my FeatureModule, they didn't intercept any request. I have to add it in the AppModule only (I guess, it is because HttpClientModule is in AppModule).
I want to understand why this is the case?? Why can't we have HttpClientModule and HTTP_INTERCEPTORS only in the FeatureModule and not in AppModule where I am not making any http calls?
To answer this question.
Only add HttpClientModule at once place at the root level. No other modules regardless of how they are imported lazy or eager even if it is from a library. Ensure that it is not importing HttpClientModule
You can however use HTTP_INTERCEPTORS providers across modules without an issue.
When you import HttpClientModule across modules and then re import that into another module it effectively resets the providers for HTTP_INTERCEPTORS for that module.
This is an intended behaviour. If you need more information about the discussion you can check: https://github.com/angular/angular/issues/20575