[generator] Disable [SupportedOSPlatform] until .NET 5/6. (#781)

Context: da12df4
Context: a33084b
Context: dotnet/android#5497 (review)

We cannot currently build `net5.0` or `net6.0` assemblies in our
xamarin-android tree; we instead do some workaround that involves
compiling with `netcoreapp3.1` while referencing the 5.0 BCL.

This creates a conflict between the local `[SupportedOSPlatform]` we
create in `Mono.Android.dll` built for `netcoreapp3.1` , and the real
one in the 5.0 BCL.

	error CS0433: The type 'SupportedOSPlatformAttribute' exists in both
	'Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065' and
	'System.Runtime, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
	[/Users/runner/work/1/s/tests/Mono.Android-Tests/Java.Interop-Tests/Java.Interop-Tests.NET.csproj]

Disable generating `SupportedOSPlatformAttribute` until we can build
`Mono.Android.dll` with `NET` defined, in which case it will not
contain the local attribute, and we can re-enable da12df4.

Author: jpobst

tests/generator-Tests/Unit-Tests/CodeGeneratorTests.cs

@@ -236,18 +236,20 @@ class XAJavaInteropCodeGeneratorTests : CodeGeneratorTests
 	{
 		protected override CodeGenerationTarget Target => CodeGenerationTarget.XAJavaInterop1;
 
-		[Test]
-		public void SupportedOSPlatform ()
-		{
-			var klass = SupportTypeBuilder.CreateClass ("java.code.MyClass", options);
-			klass.ApiAvailableSince = 30;
 
-			generator.Context.ContextTypes.Push (klass);
-			generator.WriteType (klass, string.Empty, new GenerationInfo ("", "", "MyAssembly"));
-			generator.Context.ContextTypes.Pop ();
+		// Disabled until we can properly build .NET 5/6 assemblies in our XA tree.
+		//[Test]
+		//public void SupportedOSPlatform ()
+		//{
+		//	var klass = SupportTypeBuilder.CreateClass ("java.code.MyClass", options);
+		//	klass.ApiAvailableSince = 30;
 
-			StringAssert.Contains ("[global::System.Runtime.Versioning.SupportedOSPlatformAttribute (\"android30.0\")]", builder.ToString (), "Should contain SupportedOSPlatform!");
-		}
+		//	generator.Context.ContextTypes.Push (klass);
+		//	generator.WriteType (klass, string.Empty, new GenerationInfo ("", "", "MyAssembly"));
+		//	generator.Context.ContextTypes.Pop ();
+
+		//	StringAssert.Contains ("[global::System.Runtime.Versioning.SupportedOSPlatformAttribute (\"android30.0\")]", builder.ToString (), "Should contain SupportedOSPlatform!");
+		//}
 	}
 
 	[TestFixture]

tools/generator/Java.Interop.Tools.Generator.ObjectModel/NamespaceMapping.cs

@@ -32,20 +32,21 @@ public void Generate (CodeGenerationOptions opt, GenerationInfo gen_info)
 				foreach (var jni in opt.GetJniMarshalDelegates ())
 					sw.WriteLine ($"delegate {FromJniType (jni[jni.Length - 1])} {jni} (IntPtr jnienv, IntPtr klass{GetDelegateParameters (jni)});");
 
+				// Disabled until we can properly build .NET 5/6 assemblies in our XA tree.
 				// [SupportedOSPlatform] only exists in .NET 5.0+, so we need to generate a
 				// dummy one so earlier frameworks can compile.
-				if (opt.CodeGenerationTarget == Xamarin.Android.Binder.CodeGenerationTarget.XAJavaInterop1) {
-					sw.WriteLine ("#if !NET");
-					sw.WriteLine ("namespace System.Runtime.Versioning {");
-					sw.WriteLine ("    [System.Diagnostics.Conditional(\"NEVER\")]");
-					sw.WriteLine ("    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Constructor | AttributeTargets.Event | AttributeTargets.Method | AttributeTargets.Module | AttributeTargets.Property | AttributeTargets.Struct, AllowMultiple = true, Inherited = false)]");
-					sw.WriteLine ("    internal sealed class SupportedOSPlatformAttribute : Attribute {");
-					sw.WriteLine ("        public SupportedOSPlatformAttribute (string platformName) { }");
-					sw.WriteLine ("    }");
-					sw.WriteLine ("}");
-					sw.WriteLine ("#endif");
-					sw.WriteLine ("");
-				}
+				//if (opt.CodeGenerationTarget == Xamarin.Android.Binder.CodeGenerationTarget.XAJavaInterop1) {
+				//	sw.WriteLine ("#if !NET");
+				//	sw.WriteLine ("namespace System.Runtime.Versioning {");
+				//	sw.WriteLine ("    [System.Diagnostics.Conditional(\"NEVER\")]");
+				//	sw.WriteLine ("    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Constructor | AttributeTargets.Event | AttributeTargets.Method | AttributeTargets.Module | AttributeTargets.Property | AttributeTargets.Struct, AllowMultiple = true, Inherited = false)]");
+				//	sw.WriteLine ("    internal sealed class SupportedOSPlatformAttribute : Attribute {");
+				//	sw.WriteLine ("        public SupportedOSPlatformAttribute (string platformName) { }");
+				//	sw.WriteLine ("    }");
+				//	sw.WriteLine ("}");
+				//	sw.WriteLine ("#endif");
+				//	sw.WriteLine ("");
+				//}
 			}
 		}
 

tools/generator/SourceWriters/Attributes/SupportedOSPlatformAttr.cs

@@ -15,7 +15,8 @@ public class SupportedOSPlatformAttr : AttributeWriter
 
 		public override void WriteAttribute (CodeWriter writer)
 		{
-			writer.WriteLine ($"[global::System.Runtime.Versioning.SupportedOSPlatformAttribute (\"android{Version}.0\")]");
+			// Disabled until we can properly build .NET 5/6 assemblies in our XA tree.
+			//writer.WriteLine ($"[global::System.Runtime.Versioning.SupportedOSPlatformAttribute (\"android{Version}.0\")]");
 		}
 	}
 }