Add protected to no-exposed-subject eslint rule

[butterknight]

Hey!

The no-exposed-subjects rule by default (when turned on) requires Subjects to always be private. Its documentation states that it can be configured to allow them to be protected as well. The use-case for this are abstract classes that could expose a subject to its inheriting classes.

The downside of this is that, with the new version of Angular, protected members can be accessed from the template so it could be a potential risk.

Do you think it might be beneficial enough to allow protected with this rule or should we leave it only for private as it is currently?

[thabalija]

We use protected when we have class inheritance. I think that the proper way would be to have:

• private Subject in the base class
• a protected method in a base class that updated that subject
• public Observable which is used in the template (either in base or class which extends it, depending on the needs)

This approach has a bit of a boilerplate, but I think it is "by the book" solution.

[fvoska]

I think we could allow protected subjects. This will help with inheritance and in Angular v14+ it will also work if you need just a simple subject for use in template. Since Angular 14, you can access protected members from template: https://twitter.com/angular/status/1537181658461265920?lang=en

[butterknight]

By default I'd be fully up for it, but I'm just a bit concerned whether allowing protected could be a potential risk precisely because they can now be used in the template.

[butterknight]

Is this something on what we can make a decision or do we need to discuss it further?

[fvoska]

I vote for leaving it private-only

[butterknight]

I tend to agree. Should we close this discussion?

How do we actually close this discussion? 😅

[fvoska]

[fvoska]

I have locked the discussion