[generator] Add [SupportedOSPlatform] to bound constant fields (#1038)

Context: #1037
Currently we do not add `[SupportedOSPlatform]` attributes to bound
`const` fields, which can lead to customers using them on platforms
where they are not supported:
namespace Android.Telecom {
public partial class TelecomManager : Java.Lang.Object {
[Register("ACTION_POST_CALL", ApiSince=30)]
public const string ActionPostCall = "android.telecom.action.POST_CALL";
}
}
Update `generator` so that `[SupportedOSPlatform]` is emitted for
such `const` fields:
namespace Android.Telecom {
public partial class TelecomManager : Java.Lang.Object {
[Register("ACTION_POST_CALL", ApiSince=30)]
[global::System.Runtime.Versioning.SupportedOSPlatformAttribute ("android30.0")]
public const string ActionPostCall = "android.telecom.action.POST_CALL";
}
}
Note this does not address the `enum` part of #1037, which will
require a much more involved fix.

Author: jpobst

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

@@ -736,6 +736,24 @@ public void SupportedOSPlatform ()
 
 StringAssert.Contains("[global::System.Runtime.Versioning.SupportedOSPlatformAttribute (\"android30.0\")]",builder.ToString(),"Should contain SupportedOSPlatform!");
 }
+
+[Test]
+publicvoidSupportedOSPlatformConstFields()
+{
+// Ensure we write [SupportedOSPlatform] for const fields
+varklass=newTestClass("java.lang.Object","com.mypackage.foo");
+varfield=newTestField("java.lang.String","bar").SetConstant("MY_VALUE");
+
+field.ApiAvailableSince=30;
+
+klass.Fields.Add(field);
+
+generator.Context.ContextTypes.Push(klass);
+generator.WriteType(klass,string.Empty,newGenerationInfo("","","MyAssembly"));
+generator.Context.ContextTypes.Pop();
+
+StringAssert.Contains("[global::System.Runtime.Versioning.SupportedOSPlatformAttribute (\"android30.0\")]",builder.ToString(),"Should contain SupportedOSPlatform!");
+}
 }
 
 [TestFixture]

tools/generator/SourceWriters/BoundField.cs

@@ -31,6 +31,7 @@ public BoundField (GenBase type, Field field, CodeGenerationOptions opt)
 if(field.IsEnumified)
 Attributes.Add(newGeneratedEnumAttr());
 
+SourceWriterExtensions.AddSupportedOSPlatform(Attributes,field,opt);
 SourceWriterExtensions.AddObsolete(Attributes,field.DeprecatedComment,opt,field.IsDeprecated,isError:field.IsDeprecatedError,deprecatedSince:field.DeprecatedSince);
 
 if(field.Annotation.HasValue())