Introduce ESLint rule to prevent Observable-return methods from being used in Angular templates

[ybnd]

We commonly use this pattern in DSpace Angular:

• Component method returnSomething$() returns an Observable
• Called from the template, with | async

Effectively this causes the RxJS pipe to be executed again for each change detection cycle, often leading to performance issues.

We should look into introducing an ESLint rule to guard against this.

Existing cases should be rewritten into the following pattern:

• Subscribe within ngOnInit()
• Pass emitted values to a BehaviorSubject; this will be the new target for | async
• Unsubscribe within ngOnDestroy()

[Aryakoste]

@lgeggleston I would like to work on this issue.

[lgeggleston]

Hi @Aryakoste you're assigned, thank you!