[Core] Fix ObservableLookup events

Because the groups are IList implementers, the IList overload was being
executed, giving out the wrong items in the old/new items in the change
event. Now we ensure groupings are treated as the item changed which
fixes issues in the WPF frontend bindings.

1 files changed, 71 insertions, 0 deletions

diff --git a/Xamarin.PropertyEditing.Tests/ObservableLookupTests.cs b/Xamarin.PropertyEditing.Tests/ObservableLookupTests.cs
new file mode 100644
index 0000000..f88b9b5
--- /dev/null
+++ b/Xamarin.PropertyEditing.Tests/ObservableLookupTests.cs
@@ -0,0 +1,71 @@
+using System.Collections.Specialized;
+using System.Linq;
+using NUnit.Framework;
+
+namespace Xamarin.PropertyEditing.Tests
+{
+	[TestFixture]
+	internal class ObservableLookupTests
+	{
+		[TestCase ("key")]
+		[TestCase (null)]
+		public void RemoveGroup (string key)
+		{
+			const string value = "value";
+			var lookup = new ObservableLookup<string, string> ();
+			lookup.Add (key, value);
+			Assume.That (lookup.Contains (key), Is.True);
+			Assume.That (lookup[key], Contains.Item (value));
+
+			bool groupRemoved = false;
+			lookup.CollectionChanged += (sender, args) => {
+				if (args.Action == NotifyCollectionChangedAction.Remove) {
+					var g = args.OldItems[0] as IGrouping<string, string>;
+					if (g != null && g.Key == key)
+						groupRemoved = true;
+				}
+			};
+
+			var grouping = lookup[key];
+			lookup.Remove (key);
+
+			Assert.That (groupRemoved, Is.True);
+			Assert.That (lookup, Does.Not.Contain (grouping));
+		}
+
+		[TestCase ("key")]
+		[TestCase (null)] // The reality is that null as a key receives special treatment
+		public void RemoveLastItemInGroup (string key)
+		{
+			const string value = "value";
+			var lookup = new ObservableLookup<string, string> ();
+			lookup.Add (key, value);
+			Assume.That (lookup.Contains (key), Is.True);
+			Assume.That (lookup[key], Contains.Item (value));
+
+			bool itemRemoved = false, groupRemoved = false;
+			lookup.CollectionChanged += (sender, args) => {
+				if (args.Action == NotifyCollectionChangedAction.Remove) {
+					var g = args.OldItems[0] as IGrouping<string, string>;
+					if (g != null && g.Key == key)
+						groupRemoved = true;
+				}
+			};
+
+			var grouping = lookup[key];
+			((INotifyCollectionChanged) grouping).CollectionChanged += (sender, args) => {
+				if (args.Action == NotifyCollectionChangedAction.Remove) {
+					if (args.OldItems[0] == value)
+						itemRemoved = true;
+				}
+			};
+
+			lookup.Remove (key, value);
+
+			Assert.That (itemRemoved, Is.True);
+			Assert.That (groupRemoved, Is.True);
+			Assert.That (grouping, Does.Not.Contains (value));
+			Assert.That (lookup, Does.Not.Contain (grouping));
+		}
+	}
+}