Resource loading (#815)

* Resource Loader

* Replace XamlLoader API by ResourceLoader for the Previewer

* instruct generated IL to use the resourceLoader

* [docs] update docs

* oops

* [docs] fix docs

4 files changed, 22 insertions, 13 deletions

diff --git a/Xamarin.Forms.Xaml/ApplyPropertiesVisitor.cs b/Xamarin.Forms.Xaml/ApplyPropertiesVisitor.cs
index 5b8a8403..337b2ace 100644
--- a/Xamarin.Forms.Xaml/ApplyPropertiesVisitor.cs
+++ b/Xamarin.Forms.Xaml/ApplyPropertiesVisitor.cs
@@ -305,8 +305,8 @@ namespace Xamarin.Forms.Xaml
 				return;
 
 			xpe = xpe ?? new XamlParseException($"Cannot assign property \"{localName}\": Property does not exists, or is not assignable, or mismatching type between value and property", lineInfo);
-			if (context.DoNotThrowOnExceptions)
-				System.Diagnostics.Debug.WriteLine(xpe.Message);
+			if (context.ExceptionHandler != null)
+				context.ExceptionHandler(xpe);
 			else
 				throw xpe;
 		}
diff --git a/Xamarin.Forms.Xaml/HydratationContext.cs b/Xamarin.Forms.Xaml/HydratationContext.cs
index 7273a2cc..172bce17 100644
--- a/Xamarin.Forms.Xaml/HydratationContext.cs
+++ b/Xamarin.Forms.Xaml/HydratationContext.cs
@@ -3,7 +3,7 @@ using System.Collections.Generic;
 
 namespace Xamarin.Forms.Xaml
 {
-	internal class HydratationContext
+	class HydratationContext
 	{
 		public HydratationContext()
 		{
@@ -17,8 +17,8 @@ namespace Xamarin.Forms.Xaml
 
 		public HydratationContext ParentContext { get; set; }
 
-		public bool DoNotThrowOnExceptions { get; set; }
+		public Action<Exception> ExceptionHandler { get; set; }
 
 		public object RootElement { get; set; }
 	}
-}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Xaml/XamlFilePathAttribute.cs b/Xamarin.Forms.Xaml/XamlFilePathAttribute.cs
index 615f290b..7a6d665b 100644
--- a/Xamarin.Forms.Xaml/XamlFilePathAttribute.cs
+++ b/Xamarin.Forms.Xaml/XamlFilePathAttribute.cs
@@ -3,7 +3,7 @@ using System.Runtime.CompilerServices;
 
 namespace Xamarin.Forms.Xaml
 {
-	[AttributeUsage(AttributeTargets.Class, Inherited = false)]
+	[AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
 	public sealed class XamlFilePathAttribute : Attribute
 	{
 		public XamlFilePathAttribute([CallerFilePath] string filePath = "")
diff --git a/Xamarin.Forms.Xaml/XamlLoader.cs b/Xamarin.Forms.Xaml/XamlLoader.cs
index 7fee40da..cdf73bdd 100644
--- a/Xamarin.Forms.Xaml/XamlLoader.cs
+++ b/Xamarin.Forms.Xaml/XamlLoader.cs
@@ -32,9 +32,11 @@ using System.IO;
 using System.Reflection;
 using System.Text.RegularExpressions;
 using System.Xml;
+using Xamarin.Forms.Internals;
 
 namespace Xamarin.Forms.Xaml.Internals
 {
+	[Obsolete ("Replaced by ResourceLoader")]
 	public static class XamlLoader
 	{
 		public static Func<Type, string> XamlFileProvider { get; internal set; }
@@ -44,7 +46,7 @@ namespace Xamarin.Forms.Xaml.Internals
 
 namespace Xamarin.Forms.Xaml
 {
-	internal static class XamlLoader
+	static class XamlLoader
 	{
 		static readonly Dictionary<Type, string> XamlResources = new Dictionary<Type, string>();
 
@@ -75,7 +77,9 @@ namespace Xamarin.Forms.Xaml
 					XamlParser.ParseXaml (rootnode, reader);
 					Visit (rootnode, new HydratationContext {
 						RootElement = view,
-						DoNotThrowOnExceptions = Xamarin.Forms.Xaml.Internals.XamlLoader.DoNotThrowOnExceptions
+#pragma warning disable 0618
+						ExceptionHandler = ResourceLoader.ExceptionHandler ?? (Internals.XamlLoader.DoNotThrowOnExceptions ? e => { }: (Action<Exception>)null)
+#pragma warning restore 0618
 					});
 					break;
 				}
@@ -99,7 +103,7 @@ namespace Xamarin.Forms.Xaml
 					var rootnode = new RuntimeRootNode (new XmlType (reader.NamespaceURI, reader.Name, null), null, (IXmlNamespaceResolver)reader);
 					XamlParser.ParseXaml (rootnode, reader);
 					var visitorContext = new HydratationContext {
-						DoNotThrowOnExceptions = doNotThrow,
+						ExceptionHandler = doNotThrow ? e => { } : (Action<Exception>)null,
 					};
 					var cvv = new CreateValuesVisitor (visitorContext);
 					cvv.Visit ((ElementNode)rootnode, null);
@@ -127,10 +131,14 @@ namespace Xamarin.Forms.Xaml
 
 		static string GetXamlForType(Type type)
 		{
-			string xaml = null;
-
 			//the Previewer might want to provide it's own xaml for this... let them do that
-			if (Xamarin.Forms.Xaml.Internals.XamlLoader.XamlFileProvider != null && (xaml = Xamarin.Forms.Xaml.Internals.XamlLoader.XamlFileProvider(type)) != null)
+			//the check at the end is preferred (using ResourceLoader). keep this until all the previewers are updated
+
+#pragma warning disable 0618
+			var xaml = Internals.XamlLoader.XamlFileProvider?.Invoke(type);
+#pragma warning restore 0618
+
+			if (xaml != null && ResourceLoader.ResourceProvider == null)
 				return xaml;
 
 			var assembly = type.GetTypeInfo().Assembly;
@@ -189,7 +197,8 @@ namespace Xamarin.Forms.Xaml
 				return null;
 
 			XamlResources[type] = resourceName;
-			return xaml;
+			var alternateXaml = ResourceLoader.ResourceProvider?.Invoke(resourceName);
+			return alternateXaml ?? xaml;
 		}
 
 		static bool ResourceMatchesFilename(Assembly assembly, string resource, string filename)