[core] Add tests for #9151

Xamarin.Forms.Core.UnitTests/BindableObjectUnitTests.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using NUnit.Framework;
 using Xamarin.Forms.Internals;
@@ -61,6 +62,15 @@ public Baz Qux
 		}
 	}
 
+	internal static class AttachedPropertyHolder
+	{
+		public static readonly BindableProperty AttachedCollectionProperty =
+			BindableProperty.CreateAttached("AttachedCollection", typeof(IList<string>), typeof(AttachedPropertyHolder), new List<string>());
+
+		public static IList<string> GetAttachedCollection(BindableObject bindable) => (IList<string>)bindable.GetValue(AttachedCollectionProperty);
+		public static void SetAttachedCollection(BindableObject bindable, IList<string> value) => bindable.SetValue(AttachedCollectionProperty, value);
+	}
+
 	internal class ToBarConverter : TypeConverter
 	{
 		public override object ConvertFrom(System.Globalization.CultureInfo culture, object value)
@@ -1593,5 +1603,33 @@ public void SetBindingToTextInvokesToString()
 			Assert.That(bindable.GetValue(prop), Is.EqualTo("converted"));
 		}
 
+		[Test]
+		//https://github.com/xamarin/Xamarin.Forms/issues/9151
+		public void SetValueWorksWithAttachedCollectionValuedProperties()
+		{
+			var prop = BindableProperty.CreateAttached("AttachedCollection", typeof(IList<string>), typeof(AttachedPropertyHolder), null, defaultValueCreator: _ => new List<string>());
+			var collection = new[] { "a", "b" };
+			var bindable = new MockBindable() { BindingContext = new { info = collection } };
+			bindable.SetBinding(prop, "info");
+
+			Assert.That(bindable.GetValue(prop), Is.EquivalentTo(collection));
+		}
+
+		[Test]
+		//https://github.com/xamarin/Xamarin.Forms/issues/9151
+		public void SetValueWorksWithAttachedCollectionValuedPropertiesOnMultipleBindables()
+		{
+			var prop = BindableProperty.CreateAttached("AttachedCollection", typeof(IList<string>), typeof(AttachedPropertyHolder), null, defaultValueCreator: _ => new List<string>());
+			var collection1 = new[] { "a", "b" };
+			var collection2 = new[] { "c", "d" };
+
+			var bindable1 = new MockBindable() { BindingContext = new { info = collection1 } };
+			bindable1.SetValue(prop, collection1);
+			var bindable2 = new MockBindable() { BindingContext = new { info = collection2 } };
+			bindable2.SetValue(prop, collection2);
+
+			Assert.That(bindable1.GetValue(prop), Is.EquivalentTo(collection1));
+			Assert.That(bindable2.GetValue(prop), Is.EquivalentTo(collection2));
+		}
 	}
 }

Xamarin.Forms.Xaml.UnitTests/AttachedProperties.xaml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+			 xmlns:local="clr-namespace:Xamarin.Forms.Xaml.UnitTests"
+             x:Class="Xamarin.Forms.Xaml.UnitTests.AttachedProperties">
+	<ContentPage.Content>
+        <StackLayout>
+            <StackLayout x:Name="StackLayout1">
+                <local:StackLayoutProperties.StackLayoutCollection>
+                    <local:MyCustomClass ExampleProperty1="a"/>
+                    <local:MyCustomClass ExampleProperty1="b"/>
+                </local:StackLayoutProperties.StackLayoutCollection>
+            </StackLayout>
+            <StackLayout x:Name="StackLayout2">
+                <local:StackLayoutProperties.StackLayoutCollection>
+                    <local:MyCustomClass ExampleProperty1="c"/>
+                    <local:MyCustomClass ExampleProperty1="d"/>
+                </local:StackLayoutProperties.StackLayoutCollection>
+            </StackLayout>
+        </StackLayout>
+	</ContentPage.Content>
+</ContentPage>

Xamarin.Forms.Xaml.UnitTests/AttachedProperties.xaml.cs

@@ -0,0 +1,68 @@
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public partial class AttachedProperties : ContentPage
+	{
+
+		public AttachedProperties()
+		{
+			InitializeComponent();
+		}
+
+		public AttachedProperties(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+		[TestFixture]
+		public class Tests
+		{
+			[SetUp]
+			public void Setup()
+			{
+				Device.PlatformServices = new MockPlatformServices();
+			}
+
+			[TearDown]
+			public void TearDown()
+			{
+				Device.PlatformServices = null;
+			}
+
+			[TestCase(true)]
+			[TestCase(false)]
+			public void BindProperties(bool useCompiledXaml)
+			{
+				var layout = new AttachedProperties(useCompiledXaml);
+				var collection1 = StackLayoutProperties.GetStackLayoutCollection(layout.StackLayout1);
+				var collection2 = StackLayoutProperties.GetStackLayoutCollection(layout.StackLayout2);
+				Assert.That(collection1[0].ExampleProperty1, Is.EqualTo("a"));
+				Assert.That(collection1[1].ExampleProperty1, Is.EqualTo("b"));
+				Assert.That(collection2[0].ExampleProperty1, Is.EqualTo("c"));
+				Assert.That(collection2[1].ExampleProperty1, Is.EqualTo("d"));
+			}
+		}
+	}
+
+
+	public class MyCustomClass
+	{
+		public string ExampleProperty1 { get; set; }
+	}
+
+	public class StackLayoutProperties
+	{
+		public static readonly BindableProperty StackLayoutCollectionProperty =
+			BindableProperty.CreateAttached("StackLayoutCollection",
+				typeof(IList<MyCustomClass>),
+				typeof(StackLayoutProperties),
+				null,
+				defaultValueCreator: _ => new List<MyCustomClass>());
+
+		public static IList<MyCustomClass> GetStackLayoutCollection(BindableObject view) => (IList<MyCustomClass>)view.GetValue(StackLayoutCollectionProperty);
+		public static void SetStackLayoutCollection(BindableObject view, IList<MyCustomClass> value) => view.SetValue(StackLayoutCollectionProperty, value);
+	}
+}