.net8 Android not building because Resources from resx not found.

[dellis1972]

Fixes #9163

With the release of the new Resource Designer assembly we purposely removed the existing legacy Resource.designer.cs file from the @(Compile) ItemGroup. This is so that we did not get any clashes with the new system.

Unfortunately the name Resource.designer.cs is also used by developers as the name for the generated class when using .resx files. As a result we got the above bug report because the class was disappearing.

error CS0234: The type or namespace name 'Resources' does not exist in the namespace 'StringResourcesBug' (are you missing an assembly reference?)

It turns out that the _RemoveLegacyDesigner was being a bit too aggressive with its removal of files. Because it was matching on filename only it was removing files which had nothing to do with Android Resources. This would cause the above error.

The fix in this case is to check for additional metadata. In the case of .resx file designers they typically have a DependentUpon metadata to signal that they are generated from the .resx. So we should check this metadata to make sure it is NOT set before removing a file.

A new unit test was added to test this fix and it worked. But it did show up one other issue. In certain cases we would end up with two Resource classes in the same namespace. This would then cause the following build error.

error CS0260: Missing partial modifier on declaration of type 'Resource'; another partial declaration of this type exists

This is because the two classes had different modifiers. We could also get an error if the access modifiers are different (public vs internal). So lets add a new MSBuild property AndroidResourceDesignerClassModifier. This property defaults to public, but can be overridden by the user to control the access modifier of the generated class.

Also we have to remove the GeneratedCode Attribute usage on the generated Resource class. Since it can conflict with the one that is auto added to the Resource.designer.cs generated by the resx code generator. If we leave this in place we get the following error.

__Microsoft.Android.Resource.Designer.cs(15,3,15,16): error CS0579: Duplicate 'GeneratedCode' attribute

Unfortunately the GeneratedCode Attribute [1] is marked as AllowMultiple=false and in this case there is no way to know if it exists on the class already as its a partial class.

[1] https://learn.microsoft.com/en-us/dotnet/api/system.codedom.compiler.generatedcodeattribute?view=net-8.0

[jonathanpeppers]

Otherwise, LGTM.

[jonathanpeppers]

Overall, LGTM. 👍 I reran some test lanes to check if they will be green.