[XamlC] provide backward compat for ProvideValueTarget without Target… (#583)

* [XamlC] provide backward compat for ProvideValueTarget without TargetProperty

* docs

Xamarin.Forms.Xaml/MarkupExtensions/StaticResourceExtension.cs

@@ -12,21 +12,19 @@ namespace Xamarin.Forms.Xaml
 		{
 			if (serviceProvider == null)
 				throw new ArgumentNullException(nameof(serviceProvider));
-			if (Key == null)
-			{
-				var lineInfoProvider = serviceProvider.GetService(typeof (IXmlLineInfoProvider)) as IXmlLineInfoProvider;
+			if (Key == null) {
+				var lineInfoProvider = serviceProvider.GetService(typeof(IXmlLineInfoProvider)) as IXmlLineInfoProvider;
 				var lineInfo = (lineInfoProvider != null) ? lineInfoProvider.XmlLineInfo : new XmlLineInfo();
 				throw new XamlParseException("you must specify a key in {StaticResource}", lineInfo);
 			}
-			var valueProvider = serviceProvider.GetService(typeof (IProvideValueTarget)) as IProvideParentValues;
+			var valueProvider = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideParentValues;
 			if (valueProvider == null)
 				throw new ArgumentException();
-			var xmlLineInfoProvider = serviceProvider.GetService(typeof (IXmlLineInfoProvider)) as IXmlLineInfoProvider;
+			var xmlLineInfoProvider = serviceProvider.GetService(typeof(IXmlLineInfoProvider)) as IXmlLineInfoProvider;
 			var xmlLineInfo = xmlLineInfoProvider != null ? xmlLineInfoProvider.XmlLineInfo : null;
 			object resource = null;
 
-			foreach (var p in valueProvider.ParentObjects)
-			{
+			foreach (var p in valueProvider.ParentObjects) {
 				var ve = p as VisualElement;
 				var resDict = ve?.Resources ?? p as ResourceDictionary;
 				if (resDict == null)
@@ -36,7 +34,7 @@ namespace Xamarin.Forms.Xaml
 			}
 			if (resource == null && Application.Current != null && Application.Current.Resources != null &&
 				Application.Current.Resources.ContainsKey(Key))
-				resource = Application.Current.Resources [Key];
+				resource = Application.Current.Resources[Key];
 
 			if (resource == null)
 				throw new XamlParseException($"StaticResource not found for key {Key}", xmlLineInfo);
@@ -44,12 +42,17 @@ namespace Xamarin.Forms.Xaml
 			var bp = valueProvider.TargetProperty as BindableProperty;
 			var pi = valueProvider.TargetProperty as PropertyInfo;
 			var propertyType = bp?.ReturnType ?? pi?.PropertyType;
-			if (propertyType == null)
+			if (propertyType == null) {
+				if (resource.GetType().GetTypeInfo().IsGenericType && (resource.GetType().GetGenericTypeDefinition() == typeof(OnPlatform<>) || resource.GetType().GetGenericTypeDefinition() == typeof(OnIdiom<>))) {
+					// This is only there to support our backward compat story with pre 2.3.3 compiled Xaml project who was not providing TargetProperty
+					var method = resource.GetType().GetRuntimeMethod("op_Implicit", new[] { resource.GetType() });
+					resource = method.Invoke(resource, new[] { resource });
+				}
 				return resource;
+			}
 			if (propertyType.IsAssignableFrom(resource.GetType()))
 				return resource;
 			var implicit_op = resource.GetType().GetRuntimeMethod("op_Implicit", new [] { resource.GetType() });
-			//This will invoke the op_implicit on OnPlatform<>
 			if (implicit_op != null && propertyType.IsAssignableFrom(implicit_op.ReturnType))
 				return implicit_op.Invoke(resource, new [] { resource });
 

Xamarin.Forms.Xaml/XamlServiceProvider.cs

@@ -137,6 +137,11 @@ namespace Xamarin.Forms.Xaml.Internals
 		readonly object[] objectAndParents;
 		readonly object targetProperty;
 
+		[Obsolete("TargetProperty is now supported, use it")]
+		public SimpleValueTargetProvider(object[] objectAndParents) : this (objectAndParents, null)
+		{
+		}
+
 		public SimpleValueTargetProvider(object[] objectAndParents, object targetProperty)
 		{
 			if (objectAndParents == null)

docs/Xamarin.Forms.Xaml/Xamarin.Forms.Xaml.Internals/SimpleValueTargetProvider.xml

@@ -21,7 +21,13 @@
       <MemberType>Constructor</MemberType>
       <AssemblyInfo>
         <AssemblyVersion>1.5.0.0</AssemblyVersion>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
       </AssemblyInfo>
+      <Attributes>
+        <Attribute>
+          <AttributeName>System.Obsolete("TargetProperty is now supported, use it")</AttributeName>
+        </Attribute>
+      </Attributes>
       <Parameters>
         <Parameter Name="objectAndParents" Type="System.Object[]" />
       </Parameters>