VNHumanBodyPose3DObservationJointName smart enum GetValue method linked away during optimized build

[haritha-mohan]

Ref: #19412

The xammac test fails to build when in release mode with all the optimizations enabled: stack trace.

Using tools.sln to build the app locally, I discovered the null reference exception mentioned in the trace originates from:

xamarin-macios/src/ObjCRuntime/Registrar.cs

Line 1267 in 2bd2338

foreach (var m in getValueMethods) {

The loop is trying to iterate through a null enumerable.

For an unknown reason, during the optimized release build the value extension methods for the smart enum Vision.VNHumanBodyPose3DObservationJointNameExtensions are getting linked away. This is only an issue with the Value methods as the constant methods mentioned right above this code are still present..and since the xammac debug and other release version (without the all optimizations argument passed) are passing it clarifies that its not an issue with the actual smart enum or api but just something during the linking step.

As a temp workaround, there has been an additional test added in the monotouch test suite (which is where the test code for xammac is) that uses the GetValue method to prevent it from being linked away from the time being. This allows for the xammac test to be built successfully.

Other helpful context I've come across when investigating:

• Similar stack trace when dealing with linker removing things it shouldn't: [registrar] Store the attribute type separately for availability attributes saved for the registrar. #2807
• [linker] Preserve smart enum conversion methods when needed. bdd4e48
• docs: https://learn.microsoft.com/en-us/xamarin/cross-platform/macios/binding/binding-types-reference#enum-attributes