Fix Share dialog not resolving promise when dismissed on iOS

[v-fernandez]

Summary

On iOS the promised returned by Share.share(content, options) isn't resolved if the user dismisses the dialog by either pressing "Cancel" or pressing outside the shared dialog. This PR fixes this issue.

This fixes #26809.

Changelog

[iOS] [Fixed] - Fix promised returned by Share.share(content, options) not resolving if share dialog dismissed

Test Plan

1. on iOS, open a share dialog with:

const onShare = async () => {
  const result = await Share.share({ message: 'example message' });
}

2. Dismiss the opened share dialog and the returned promised should resolve.

[tomtargosz]

So it looks like this is because of my PR (#26429). I added this check because we need to have some sort of guard against the success callback being called multiple times. Is there a way we can know that the ActionSheet was closed so we can do if (completed || dismissed)?

[tomtargosz]

@v-fernandez so I think we can change the check to:
if (completed || activityType == nil)

It looks like in completionWithItemsHandler the activityType will only be nil if the user closed the ShareSheet themselves, like so:

Here's when they close the reminders modal:

And the photos modal:

This should fix the current issue without reintroducing the crash.

[v-fernandez]

@tomtargosz makes sense. I'll update the PR with this. Thanks for the help!

[cpojer]

Nice, thank you!

[facebook-github-bot]

@cpojer is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[react-native-bot]

This pull request was successfully merged by @v-fernandez in 7468a6c.

^{When will my fix make it into a release? | Upcoming Releases}

[franciscomorais]

When is this PR going to be picked?

[dpolkovnikov]

When is this PR going to be picked?

https://github.com/facebook/react-native/releases/tag/v0.62.0-rc.0