Add postDistributedNotifications matcher for testing DistributedNotificationCenter

[fabianmuecke]

This is a workaround for postNotification not working at all on Catalina, due to Catalina not calling any observers subscribed to "nil" name.

Checklist - While not every PR needs it, new features should consider this list:

• Does this have tests?
• Does this have documentation?
• Does this break the public API (Requires major version bump)?
• Is this a new feature (Requires minor version bump)?

[ikesyo]

Thanks for submitting the pull request!

postNotification not working at all on Catalina, due to Catalina not calling any observers subscribed to "nil" name.

We don't see such breakage on our CI tests so I'm confused 🤔 We use GitHub Actions and the environment is Catalina:

https://help.github.com/en/actions/reference/virtual-environments-for-github-hosted-runners#supported-runners-and-hardware-resources

macOS Catalina 10.15

And also I can't find any description about the behavioral change at https://developer.apple.com/documentation/foundation/notificationcenter/1411723-addobserver.

[fabianmuecke]

Then it is probably limited to DistributedNotificationCenter. It is indeed an undocumented change, but Apple acknowledged it exists. See: https://mjtsai.com/blog/2019/10/04/nsdistributednotificationcenter-no-longer-supports-nil-names/ for more.

[ikesyo]

Thanks for the input, I didn't know DistributedNotificationCenter at all (I'm an iOS app developer 😄 ). Then I recommend you to add a postNotifications overload which takes DistributedNotificationCenter over NotificationCenter and make names parameter non-nil, leaving the existing matchers as is. That should make the situation/constraint clear (notification names are mandatory for DistributedNotificationCenter).

[fabianmuecke]

Sounds good.

[fabianmuecke]

Tried to implement your suggestion. Unfortunately users still won't be forced to use the function with the names parameter, as the DistributedNotificationCenter inherits from NotificationCenter and the function without names would still be valid for the compiler. Therefore I added it as a new function called postDistributedNotification, trying to make it clearer that this is intended for working with DistributedNotificationCenter. Also please note that the tests will fail, if not using toEventually, as the DistributedNotificationCenter works async, even if using deliverImmediately: true.

[ikesyo]

LGTM, thanks for the contribution! 👍