From 8dccf2f43933ed1e5fd8cb2cebbc491f5c57a8ac Mon Sep 17 00:00:00 2001
From: Stephane Delcroix <stephane@delcroix.org>
Date: Wed, 6 Mar 2019 09:39:12 +0100
Subject: [PATCH] [XamlC] throw on invalid DataType (#5335)

Invalid x:DataType was ignored up to now. Change the behavior so it
throws a XPE.

- fixes #5330
---
 Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs  |  6 +++-
 Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml    |  8 ++++++
 Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml.cs | 32 ++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml
 create mode 100644 Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml.cs

diff --git a/Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs b/Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs
index 5d6194a..c02070b 100644
--- a/Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs
+++ b/Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs
@@ -378,8 +378,12 @@ namespace Xamarin.Forms.Build.Tasks
 					break;
 				n = n.Parent as IElementNode;
 			}
+
+			if (dataTypeNode is null)
+				yield break;
+
 			if (!((dataTypeNode as ValueNode)?.Value is string dataType))
-				yield break; //throw
+				throw new XamlParseException("x:DataType expects a string literal", dataTypeNode as IXmlLineInfo);
 
 			var prefix = dataType.Contains(":") ? dataType.Substring(0, dataType.IndexOf(":", StringComparison.Ordinal)) : "";
 			var namespaceuri = node.NamespaceResolver.LookupNamespace(prefix) ?? "";
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml
new file mode 100644
index 0000000..162f20c
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml
@@ -0,0 +1,8 @@
+<?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.Gh5330"
+        x:DataType="{x:Type Button}">
+    <Label Text="{Binding foo}" />
+</ContentPage>
diff --git a/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml.cs b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml.cs
new file mode 100644
index 0000000..f480a03
--- /dev/null
+++ b/Xamarin.Forms.Xaml.UnitTests/Issues/Gh5330.xaml.cs
@@ -0,0 +1,32 @@
+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 Gh5330 : ContentPage
+	{
+		public Gh5330() => InitializeComponent();
+		public Gh5330(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;
+
+			[Test]
+			public void FailOnUnresolvedDataType([Values(true)]bool useCompiledXaml)
+			{
+				if (useCompiledXaml)
+					Assert.Throws<XamlParseException>(() => MockCompiler.Compile(typeof(Gh5330)));
+			}
+		}
+	}
+}
-- 
2.7.4