[Core] Don't leave phantom categories from grouped types

Author: Eric Maupin

Xamarin.PropertyEditing.Tests/PanelViewModelTests.cs

@@ -209,7 +209,7 @@ public async Task PropertyListCategoryFiltered ()
 		[Test]
 		public async Task PropertyListCategoryGroupedWithNullCategory ()
 		{
-			// Purposefully a null catgory
+			// Purposefully a null category
 			var normalProp = new Mock<IPropertyInfo> ();
 			normalProp.SetupGet (p => p.Type).Returns (typeof(string));
 			normalProp.SetupGet (p => p.Name).Returns ("name");
@@ -414,6 +414,34 @@ public void AutoExpandChosenGroups ()
 			Assert.That (vm.GetIsExpanded (normalProp.Object.Category), Is.True);
 		}
 
+		[Test]
+		public void GroupedTypesDoNotLeavePhantomCategory ()
+		{
+			var target = new object ();
+
+			var property = new Mock<IPropertyInfo> ();
+			property.SetupGet (p => p.Type).Returns (typeof (string));
+			property.SetupGet (p => p.Category).Returns ((string)null);
+			property.SetupGet (p => p.Name).Returns ("name");
+
+			var provider = new Mock<IEditorProvider> ();
+			provider.Setup (ep => ep.GetObjectEditorAsync (target))
+				.ReturnsAsync (new MockObjectEditor (property.Object) { Target = target });
+
+			var platform = new TargetPlatform (provider.Object) {
+				GroupedTypes = new Dictionary<Type, string> {
+					{ typeof(string), "strings" }
+				}
+			};
+
+			var vm = CreateVm (platform);
+			vm.ArrangeMode = PropertyArrangeMode.Category;
+			vm.AutoExpand = true;
+			vm.SelectedObjects.Add (target);
+
+			Assert.That (vm.ArrangedEditors.Count, Is.EqualTo (1));
+		}
+
 		internal override PanelViewModel CreateVm (TargetPlatform platform)
 		{
 			return new PanelViewModel (platform);

Xamarin.PropertyEditing/ViewModels/PanelViewModel.cs

@@ -246,10 +246,11 @@ protected override void OnAddEditors (IEnumerable<EditorViewModel> editors)
 					}
 				}
 
-				string key = grouping.Key ?? String.Empty;
-				if (remainingItems != null) // TODO: pretty sure this was out of order before, add test
-					this.arranged.Add (key, new PanelGroupViewModel (key, grouping.Where (evm => remainingItems.Contains (evm))));
-				else
+				string key = grouping.Key;
+				if (remainingItems != null) {// TODO: pretty sure this was out of order before, add test
+					if (remainingItems.Count > 0)
+						this.arranged.Add (key, new PanelGroupViewModel (key, grouping.Where (evm => remainingItems.Contains (evm))));
+				} else
 					this.arranged.Add (key, new PanelGroupViewModel (key, grouping, separateUncommon: !isFlat));
 
 				AutoExpandGroup (key);