Feedback received from engineering:

Short answer: always unsubscribe.
Slightly longer answer: It's easier to just always unsubscribe than try to learn exactly when you need to.
👍 and when you need to can be super subtle and dependent on interceptors, etc.
Best practice is to always unsubscribe when a component is destroyed.

@bob-watson that's great and as I wrote above this is exactly what I recommend my team to do, but can we please have it written in the documentation, instead of just having the generic mention of the async pipe?

Related to this topic, another pain point that I struggled to convince my team about is to never subscribe to such observables in (singleton) services, at least not without an extra mechanism to unsubscribe from the previous observable before creating a new one. I suppose this should be obvious coming from the recommendation to always unsubscribe when a component is destroyed, but again, would be nice to clarify in the documentation.

Under "Starting the request", added the following note:

You should always unsubscribe from an observable when a component is destroyed. You can use the AsyncPipe to subscribe to and unsubscribe from an observable automatically.

@pkozlowski-opensource sorry, I don't think I understand how this is solving the issue here. It's been stated that the documentation of HttpClient is not clear regarding the need to unsubscribe.
Here we have https://stackoverflow.com/a/35043309/6456946 a lot of discussion regarding the topic and it shows how different opinions devs have. Now it would be fair if angular provided their recommendation as to if and why.
@digeomel do you agree?

@Tomassito @pkozlowski-opensource @ileil I would word it slightly different, explaining why always unsubscribing is important:

You should always unsubscribe from observables, even those created by the HttpService, because of edge cases (e.g. slow network) where the built-in unsubscribe mechanism may not kick in when the component is destroyed. When the observable is used in a component, you can use the AsyncPipe in the component template to achieve this.

But the line added by @ileil and the clarifications provided here are already an improvement 😄 👍🏼 Maybe we can link to this discussion from the docs?

Yes, there should be definitely more information on what to expect from the observables exposed by angular services, especially the httpClient. Do docs even mention the fact that an http request auto completes?

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