Angular Library base class without any decorator but using Angular features

Question

I came across this in the Angular migration guide.

https://angular.io/guide/migration-undecorated-classes

I'm a library author. Should I add the @Directive() decorator to base classes?

As support for selectorless decorators is introduced in Angular version 9, if you want to support Angular version 8 and earlier, you shouldn't add a selectorless @Directive() decorator. You can either add @Directive() with a selector or move the Angular-specific features to affected subclasses.

I then checked our code library to find that there are some base classes that still don't have any decorators but is running in Angular V11. I don't see any compile errors nor linting errors.

There are many such base classes that uses angular features, hostbinding etc but still without a decorator. Is there a linting rule or some way with which we can catch these?

Answer 1

I later figured out that with Ivy Compiler such classes without decorators are caught at compile time: NG2007: Class is using Angular features but is not decorated. Please add an explicit Angular decorator.