[mail-composer][android] fix composeAsync not resolving after send/ discard

[keith-kurak]

Why

Fixes #20509

How

TL;DR - this fix restores the documented behavior, albeit with a visual bug that seems to be peculiar to Gmail.

I first tried to compare the send/ resolve flow to (what I thought) was the closest analog, expo-sms. The onHostResume lifecycle listener event is trigged in the SMS package, but not mail composer. Nothing along these lines worked (e.g., matching the Intent flags).

It turns out that expo-sharing is perhaps a more appropriate comparison, because they both use Intent.createChooser to create a share sheet (the mail composer's sheet mainly filters on email apps and can pass additional email-related keys). It seems like onHostResume never responds to returning from a share sheet. Sharing uses the ActivityEventListener instead.

Anyway, this works, with one visual quirk that seems to be peculiar to the implementation of the Gmail client's new mail activity. Pressing back does not discard the email/ return to the app. It takes you back to your inbox. Once you do this, your only choice is to use the task switcher/ launcher to leave the email, and, in the task switcher, the image of the app doesn't update, continuing to show a picture of the email that you were composing.

Other apps demonstrate the same issue with sharing to Gmail (e.g., Twitter), though others don't (e.g., Facebook). Seems possible that this is related to task/ activity settings outside the control of this package, e.g., android:launchMode.

Comparing to external packages that fulfill a similar purpose, I found some (e.g., react-native-mail) that resolve the promise as soon as the share sheet opens, which is an option, but would break the documented behavior and not match iOS.

Test Plan

Scenarios:

• single email client (bypasses chooser)
• multiple email clients (shows chooser)
• send email (returns to app, promise resolves)
• discard email (returns to app, promise resolves)
• share email, open task switcher, return to app (promise resolves, but task switcher freezes on email client)
• test with latest Expo Go unversioned as of 2/1/2023

See video (including visual bug at the end)

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for expo prebuild & EAS Build (eg: updated a module plugin).

[linear]

CX-189 Android Mail Composer not returning after finishing

Seems like SMS does it sometimes on Snack, but not always (odd), even though it uses the same code.

Would also be nice if these used the same/ similar return types #20509

[lukmccall]

LGTM ✅