Question Unsolvable compilation errors that show up as soon as Unity IAP package is imported.

I tried integrating Unity IAP package (from the package manager) into my project (empty project for now), only to be met with very strange compilation errors

Happens in Unity 2019.4.33f1 and Unity 2019.4.36f1. They are:

Library\PackageCache\com.unity.purchasing@4.1.3\Runtime\AppleCore\INativeAppleStore.cs(5,42): error CS0122: 'UnityPurchasingCallback' is inaccessible due to its protection level

and

Microsoft (R) Visual C# Compiler version 2.9.1.65535 (9d34608e)
Copyright (C) Microsoft Corporation. All rights reserved.
error CS1704: An assembly with the same simple name 'Purchasing.Common' has already been imported. Try removing one of the references (e.g. 'E:\_Unity2k19\UnityA12Test\Library\ScriptAssemblies\Purchasing.Common.dll') or sign them to enable side-by-side.


I am totally clueless as to the raison d'etre of these errors, given that they do not originate from scripts I wrote. Can anyone please help me out with this? What could be causing this error and how can I resolve it.

 

As mentioned in my post, the project is completely empty, no scripts, no assets, just a brand new project (I faced this issue while using 2019.4.33f1, I thought it was a Unity version problem, so I downloaded the latest version to give it a try and unfortunately the issue is still present). The project is empty. I just created an empty project, switched to Android (Target Android) and imported IAP, then got this error. All of my projects are in Unity 2019.4.21f1 and Unity does not have this IAP caused compilation error..IAP just works just fine with 2019.4.21f1.

I am doing all my best to move to the latest version of Unity 2019.x because none of my apps would install on any device running Android 12. Google Play won't accept any of my updates targeting Android 12, due to the android:export=true issue. I tried all sorts of fixes on this forum and from the internet, all to no avail. From what I read, the said issue with the manifest file has been automatically fixed starting with Unity 2019.4.33f1. Unfortunately I can't move my projects to these Unity versions because to the problems mentioned in this post.

 

Can I please know what you mean by " it's only with 2019.4.33f1". Do you mean the Android 12 issue is fixed ONLY with Unity 2019.4.33f1?

"You only install IAP from Package Manager, not from the Services window. Do not Import if prompted." I guess that's what I did wrong. I imported also from the Services window. Actually, I saw a warning on the services Window prohibiting me from clicking "import". I went ahead to do it because after installing the IAP package from the package manager, there was no noticeable change. I generally verify a proper installation of the IAP package by going to Window>Unity IAP> Create IAP button. But after installing IAP from the package manager (the errors mentioned in my post don't show up after I do this) nothing happens, "Unity IAP" isn't even present in the Window section. So I go ahead to import from the services window (which I used to do in the past to get IAP working), which seems to then cause all the trouble I am currently facing. So please, how should I go about fixing this? How should I get IAP properly installed and functioning (able to even edit the IAP catalog from the Window menu) without importing from the Services section as I used to do in the past.

 

"Can you try with IAP 2020/2021 versions?" Where do I get these versions? From the asset store?

If by "it's only with 2019.4.33f1" you meant the issue only occurs with 2019.4.33f1, that's not the case, it also occurs with Unity 2019.4.36f1.