[in_app_purchase] Fix wrong _pendingCompletePurchase flag value

[malsabbagh]

Description

When purchasing the _pendingCompletePurchase flag is always set to false as we were not using the setter that was setting _pendingCompletePurchase to true when purchasing status was true.

Related Issues

flutter/flutter#49083

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[cyanglaz]

Thanks for the PR! The fix is great! Would you mind add some tests before we land the PR?

[cyanglaz]

LGTM! Thank you very much!

[malsabbagh]

np :)

[d0bry]

To clarify, now pendingCompletePurchase remains true after completion.

If this is intended then the name may be misleading (after migration to Play Billing Library 2.0, I thought on Android it means 'not yet acknowledged'). Anyway, this may only result in redundant completePurchase calls, which is no harm.

[malsabbagh]

Yea I was thinking about that use case as well. But then as you said extra calls to completePurchase won't cause issues.

[cyanglaz]

@d0bry The purchases are not considered completed unless a completePurchase is called. So I guess the name is fitting. However, I think we should make our documentation clearer about this terminology.

[d0bry]

@cyanglaz Yes, I just meant that pendingCompletePurchase may suggest the purchase is not yet completed, even if it is (after completePurchase has already been called).