[Xaml[C]] throw meaningful exception while trying to set the content … (#714)

* [Xaml[C]] throw meaningful exception while trying to set the content of a property without ContentPropertyAttribute

* fix test

Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs

@@ -128,7 +128,7 @@ namespace Xamarin.Forms.Build.Tasks
 				// Collection element, implicit content, or implicit collection element.
 				string contentProperty;
 				var parentVar = Context.Variables[(IElementNode)parentNode];
-				if (parentVar.VariableType.ImplementsInterface(Module.ImportReference(typeof (IEnumerable))))
+				if (parentVar.VariableType.ImplementsInterface(Module.ImportReference(typeof (IEnumerable))) && parentVar.VariableType.GetMethods(md => md.Name == "Add" && md.Parameters.Count == 1, Module).Any())
 				{
 					var elementType = parentVar.VariableType;
 					if (elementType.FullName != "Xamarin.Forms.ResourceDictionary" && elementType.Resolve().BaseType.FullName != "Xamarin.Forms.ResourceDictionary")
@@ -152,7 +152,8 @@ namespace Xamarin.Forms.Build.Tasks
 					if (parentNode is IElementNode && ((IElementNode)parentNode).SkipProperties.Contains (propertyName))
 						return;
 					Context.IL.Append(SetPropertyValue(Context.Variables[(IElementNode)parentNode], name, node, Context, node));
-				}
+				} else
+					throw new XamlParseException($"Can not set the content of {((IElementNode)parentNode).XmlType.Name} as it doesn't have a ContentPropertyAttribute", node);
 			}
 			else if (IsCollectionItem(node, parentNode) && parentNode is ListNode)
 			{

Xamarin.Forms.Xaml.UnitTests/Issues/Bz43694.xaml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+	xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+	x:Class="Xamarin.Forms.Xaml.UnitTests.Bz43694">
+	<ContentPage.Resources>
+		<ResourceDictionary>
+			<x:String x:Key="Dark">Dark</x:String>
+			<x:String x:Key="Light">
+				<OnPlatform x:TypeArguments="x:String">
+					<OnPlatform.iOS>OpenSans-Light</OnPlatform.iOS>
+					<OnPlatform.Android>OpenSans-Light</OnPlatform.Android>
+					<OnPlatform.WinPhone>/Assets/Fonts/OpenSans-Light.ttf#Open Sans</OnPlatform.WinPhone>
+				</OnPlatform>
+			</x:String>
+		</ResourceDictionary>
+	</ContentPage.Resources>
+	<Label Text="{StaticResource Light}" 
+		VerticalOptions="Center"
+		HorizontalOptions="Center"
+		x:Name="label"/>
+</ContentPage>

Xamarin.Forms.Xaml.UnitTests/Issues/Bz43694.xaml.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	[XamlCompilation(XamlCompilationOptions.Skip)]
+	public partial class Bz43694 : ContentPage
+	{
+		public Bz43694()
+		{
+			InitializeComponent();
+		}
+
+		public Bz43694(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture]
+		class Tests
+		{
+			[SetUp]
+			public void Setup()
+			{
+				Device.PlatformServices = new MockPlatformServices();
+			}
+
+			[TearDown]
+			public void TearDown()
+			{
+				Device.PlatformServices = null;
+			}
+
+			[TestCase(true)]
+			[TestCase(false)]
+			public void xStaticWithOnPlatformChildInRD(bool useCompiledXaml)
+			{
+				if (useCompiledXaml)
+					Assert.Throws(new XamlParseExceptionConstraint(9, 6), () => MockCompiler.Compile(typeof(Bz43694)));
+				else
+					Assert.Throws(new XamlParseExceptionConstraint(9, 6), () => new Bz43694(useCompiledXaml));
+			}
+		}
+	}
+}

Xamarin.Forms.Xaml.UnitTests/Xamarin.Forms.Xaml.UnitTests.csproj

@@ -433,6 +433,9 @@
     <Compile Include="DefaultCtorRouting2.xaml.cs">
       <DependentUpon>DefaultCtorRouting2.xaml</DependentUpon>
     </Compile>
+    <Compile Include="Issues\Bz43694.xaml.cs">
+      <DependentUpon>Bz43694.xaml</DependentUpon>
+    </Compile>
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <Import Project="..\.nuspec\Xamarin.Forms.Debug.targets" />
@@ -787,6 +790,9 @@
     <EmbeddedResource Include="DefaultCtorRouting2.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="Issues\Bz43694.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />

Xamarin.Forms.Xaml/ApplyPropertiesVisitor.cs

@@ -121,7 +121,7 @@ namespace Xamarin.Forms.Xaml
 			} else if (IsCollectionItem(node, parentNode) && parentNode is IElementNode) {
 				// Collection element, implicit content, or implicit collection element.
 				string contentProperty;
-				if (typeof(IEnumerable).GetTypeInfo().IsAssignableFrom(Context.Types [parentElement].GetTypeInfo())) {
+				if (typeof(IEnumerable).GetTypeInfo().IsAssignableFrom(Context.Types [parentElement].GetTypeInfo()) && Context.Types[parentElement].GetRuntimeMethods().Any(mi => mi.Name == "Add" && mi.GetParameters().Length == 1)) {
 					var source = Values [parentNode];
 					if (!(typeof(ResourceDictionary).IsAssignableFrom(Context.Types [parentElement]))) {
 						var addMethod =
@@ -137,7 +137,8 @@ namespace Xamarin.Forms.Xaml
 
 					var source = Values [parentNode];
 					SetPropertyValue(source, name, value, Context.RootElement, node, Context, node);
-				}
+				} else
+					throw new XamlParseException($"Can not set the content of {((IElementNode)parentNode).XmlType.Name} as it doesn't have a ContentPropertyAttribute", node);
 			} else if (IsCollectionItem(node, parentNode) && parentNode is ListNode) {
 				var parentList = (ListNode)parentNode;
 				var source = Values [parentNode.Parent];