Fix when running in MSBuild / netstandard2.0 context

Author: jonathanpeppers

src/Java.Interop.Tools.TypeNameMappings/Java.Interop.Tools.TypeNameMappings/JavaNativeTypeManager.cs

@@ -167,10 +167,6 @@ public static string ToJniName (Type type)
 				"java/lang/Object";
 		}
 
-		static readonly Lazy<Type> IJavaPeerableType = new Lazy<Type> (() =>
-			Type.GetType ("Java.Interop.IJavaPeerable, Java.Interop", throwOnError: true)!
-		);
-
 		static string? ToJniName (Type type, ExportParameterKind exportKind)
 		{
 			if (type == null)
@@ -182,14 +178,29 @@ public static string ToJniName (Type type)
 			if (type == typeof (string))
 				return "java/lang/String";
 
-			if (IJavaPeerableType.Value.IsAssignableFrom (type))
+			if (ShouldCheckSpecialExportJniType (type))
 				return GetSpecialExportJniType (type.FullName!, exportKind);
 
 			return ToJniName (type, t => t.DeclaringType!, t => t.Name, GetPackageName, t => {
 				return ToJniNameFromAttributes (t);
 			}, _ => false);
 		}
 
+#if !NETSTANDARD2_0
+		static readonly Lazy<Type> IJavaPeerableType = new Lazy<Type> (() =>
+			Type.GetType ("Java.Interop.IJavaPeerable, Java.Interop", throwOnError: true)!
+		);
+#endif
+
+		// NOTE: NETSTANDARD2_0 could be running in an MSBuild context where Java.Interop.dll is not available.
+		// Trimming warnings are not enabled for netstandard2.0 in this project.
+		static bool ShouldCheckSpecialExportJniType (Type type) =>
+#if NETSTANDARD2_0
+			type.GetInterfaces ().Any (t => t.FullName == "Java.Interop.IJavaPeerable");
+#else
+			IJavaPeerableType.Value.IsAssignableFrom (type);
+#endif
+
 		public static string ToJniName (string jniType, int rank)
 		{
 			if (rank == 0)