Open Radar

 
Action Extensions should be able to query host app at least one the following:
1. whether it will use the returning items supplied in NSExtensionContext.completeRequestReturningItems.
2. its bundle id.

Reason:

"An Action extension helps users view or transform content originating in a host app. For example, an Action extension might help users edit an image in a document that they’re viewing in a text editor." —— quote from App Extension Programming Guide

So as an image editor, it is very reasonable that I add a Done button that sends edited image back to the host app.

However, currently very few apps really use the return results from Action Extensions. The end result is that my Done button confuses or even misleads users to believe the host app would update its content to the edited image from my App Extension. When they find out that it is not the case they get angry with me because they think it is my Action Extension that loses their work.

If Action Extension can query the host app whether it will use the returning items I can adjust the UI of my Action Extension accordingly:
* Show a Done button, if so
* Show a Close button and warn users that they are going to lose the work if they close it without saving or sharing by other way, if not

If the first kind of query is not supported then I'd like to at least know the host app's bundle id, so that I can collect a list of apps that use returning items and only show Done button when my Action Extension is invoked by them.