From a222bf9239f5c4333c480797bc5b6d982a923b4c Mon Sep 17 00:00:00 2001
From: Giuseppe Lippolis <workgroupengineering@outlook.com>
Date: Wed, 12 Aug 2020 11:10:10 +0200
Subject: [PATCH] Add test to check ViewModel is Collected

---
 src/Avalonia.Base/Properties/AssemblyInfo.cs  |  1 +
 .../Data/BindingTests_Method.cs               | 46 ++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Properties/AssemblyInfo.cs b/src/Avalonia.Base/Properties/AssemblyInfo.cs
index 692982cdc6..13b247de51 100644
--- a/src/Avalonia.Base/Properties/AssemblyInfo.cs
+++ b/src/Avalonia.Base/Properties/AssemblyInfo.cs
@@ -9,3 +9,4 @@ using Avalonia.Metadata;
 [assembly: InternalsVisibleTo("Avalonia.UnitTests")]
 [assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")]
 [assembly: InternalsVisibleTo("Avalonia.Controls.DataGrid")]
+[assembly: InternalsVisibleTo("Avalonia.Markup.Xaml.UnitTests")]
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_Method.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_Method.cs
index e1a7803821..7931912649 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_Method.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_Method.cs
@@ -1,4 +1,5 @@
-using System.ComponentModel;
+using System;
+using System.ComponentModel;
 using Avalonia.Controls;
 using Avalonia.Input;
 using Avalonia.UnitTests;
@@ -140,6 +141,49 @@ namespace Avalonia.Markup.Xaml.UnitTests.Data
             }
         }
 
+        [Fact]
+        public void Binding_Method_To_Command_Collected()
+        {
+            WeakReference<ViewModel> MakeRef()
+            {
+                var weakVm = new WeakReference<ViewModel>(null);
+                {
+                    var vm = new ViewModel()
+                    {
+                        Parameter = null,
+                    };
+                    weakVm.SetTarget(vm);
+                    var canExecuteCount = 0;
+                    var action = new Action<object>(vm.Do);
+                    var command = new Avalonia.Data.Converters.MethodToCommandConverter(action);
+                    command.CanExecuteChanged += (s, e) => canExecuteCount++;
+                    vm.Parameter = 0;
+                    Threading.Dispatcher.UIThread.RunJobs();
+                    vm.Parameter = null;
+                    Threading.Dispatcher.UIThread.RunJobs();
+                    Assert.Equal(2, canExecuteCount);
+                }
+                return weakVm;
+            }
+            bool IsAlive(WeakReference<ViewModel> @ref)
+            {
+                return @ref.TryGetTarget(out var instance)
+                    && instance is null == false;
+            }
+
+            var vmref = MakeRef();
+
+            var beforeCollect = IsAlive(vmref);
+
+            GC.Collect();
+            GC.WaitForPendingFinalizers();
+
+            var afterCollect = IsAlive(vmref);
+
+            Assert.True(beforeCollect, "Invalid ViewModel instance, it is already collected.");
+            Assert.False(afterCollect, "ViewModel instance was not collected");
+        }
+
         static void PerformClick(Button button)
         {
             button.RaiseEvent(new KeyEventArgs