What happen if you import the same module twice?
No problem! You can import the same module twice but Angular does not like modules with circular references and raise the circular dependency warnings on builds.
Actually, the module helps you to organize an application into associative blocks of functionality.
For example – Class-A and Class-B can absolutely be in the same file if needed. This warning is not an opinion on bad behavior.
What kinds of modules should I have and how should I use them?
Every app is different. Developers have various levels of experience and comfort with the available choices.
Some suggestions and guidelines appear to have broad appeal.
3. Feature Modules - Domain, Routed, Routing, Service, and Widget