fix for WhenAny WhenAnyValue ToProperty

src/ReactiveUI.Fody.Helpers/ObservableAsPropertyExtensions.cs

@@ -33,8 +33,8 @@ public static class ObservableAsPropertyExtensions
         /// </exception>
         public static ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(
             this IObservable<TRet> item,
-            TObj? source,
-            Expression<Func<TObj, TRet?>> property,
+            TObj source,
+            Expression<Func<TObj, TRet>> property,
             bool deferSubscription = false,
             IScheduler? scheduler = null)
             where TObj : ReactiveObject
@@ -88,8 +88,8 @@ public static ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(
         /// </exception>
         public static ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(
             this IObservable<TRet> item,
-            TObj? source,
-            Expression<Func<TObj, TRet?>> property,
+            TObj source,
+            Expression<Func<TObj, TRet>> property,
             TRet initialValue,
             bool deferSubscription = false,
             IScheduler? scheduler = null)

src/ReactiveUI.Fody.Tests/API/ApiApprovalTests.ReactiveUIFody.net5.0.approved.txt

@@ -14,9 +14,9 @@ namespace ReactiveUI.Fody.Helpers
     }
     public static class ObservableAsPropertyExtensions
     {
-        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj? source, System.Linq.Expressions.Expression<System.Func<TObj, TRet?>> property, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
+        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj source, System.Linq.Expressions.Expression<System.Func<TObj, TRet>> property, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
             where TObj : ReactiveUI.ReactiveObject { }
-        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj? source, System.Linq.Expressions.Expression<System.Func<TObj, TRet?>> property, TRet initialValue, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
+        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj source, System.Linq.Expressions.Expression<System.Func<TObj, TRet>> property, TRet initialValue, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
             where TObj : ReactiveUI.ReactiveObject { }
     }
     [System.AttributeUsage(System.AttributeTargets.Property | System.AttributeTargets.All)]

src/ReactiveUI.Fody.Tests/API/ApiApprovalTests.ReactiveUIFody.netcoreapp3.1.approved.txt

@@ -14,9 +14,9 @@ namespace ReactiveUI.Fody.Helpers
     }
     public static class ObservableAsPropertyExtensions
     {
-        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj? source, System.Linq.Expressions.Expression<System.Func<TObj, TRet?>> property, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
+        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj source, System.Linq.Expressions.Expression<System.Func<TObj, TRet>> property, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
             where TObj : ReactiveUI.ReactiveObject { }
-        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj? source, System.Linq.Expressions.Expression<System.Func<TObj, TRet?>> property, TRet initialValue, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
+        public static ReactiveUI.ObservableAsPropertyHelper<TRet> ToPropertyEx<TObj, TRet>(this System.IObservable<TRet> item, TObj source, System.Linq.Expressions.Expression<System.Func<TObj, TRet>> property, TRet initialValue, bool deferSubscription = false, System.Reactive.Concurrency.IScheduler? scheduler = null)
             where TObj : ReactiveUI.ReactiveObject { }
     }
     [System.AttributeUsage(System.AttributeTargets.Property | System.AttributeTargets.All)]

src/ReactiveUI.Splat.Tests/ReactiveUI.Splat.Tests.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>netcoreapp3.1;net5.0</TargetFrameworks>
@@ -10,7 +10,7 @@
 
   <ItemGroup>
     <PackageReference Include="Splat.Autofac" Version="12.*" />
-    <PackageReference Include="Splat.DryIoc" Version="11.*" />
+    <PackageReference Include="Splat.DryIoc" Version="12.*" />
     <PackageReference Include="Splat.Ninject" Version="12.*" />
   </ItemGroup>
 

src/ReactiveUI.Tests/Mocks/MockBindListView.cs

@@ -55,7 +55,7 @@ public MockBindListView()
                     .Where(i => i != null)
                     .Cast<MockBindListItemViewModel>()
                     .Do(_ => ItemList.UnselectAll())
-                    .InvokeCommand(this, v => v.ViewModel!.SelectItem).DisposeWith(d);
+                    .InvokeCommand(this, v => v!.ViewModel!.SelectItem).DisposeWith(d);
             });
         }
 

src/ReactiveUI.Tests/ObservableAsPropertyHelper/ObservableAsPropertyHelperTest.cs

@@ -456,13 +456,13 @@ public void ToProperty_NameOf_ValidValuesProduced(string[] testWords, string[] f
 
             fixture.ObservableForProperty(x => x.LastThreeLettersOfOneWord, beforeChange: true).ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var lastThreeChanging).Subscribe();
 
-            var changing = new[] { firstThreeChanging, lastThreeChanging };
+            var changing = new[] { firstThreeChanging!, lastThreeChanging };
 
             fixture.ObservableForProperty(x => x.FirstThreeLettersOfOneWord, beforeChange: false).ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var firstThreeChanged).Subscribe();
 
             fixture.ObservableForProperty(x => x.LastThreeLettersOfOneWord, beforeChange: false).ToObservableChangeSet(ImmediateScheduler.Instance).Bind(out var lastThreeChanged).Subscribe();
 
-            var changed = new[] { firstThreeChanged, lastThreeChanged };
+            var changed = new[] { firstThreeChanged!, lastThreeChanged };
 
             Assert.True(changed.All(x => x.Count == 0));
             Assert.True(changing.All(x => x.Count == 0));
@@ -551,11 +551,11 @@ public void NullableTypesTestShouldntNeedDecorators2_ToProperty()
             fixture.WhenAnyValue(
                 x => x.ProjectService.ProjectsNullable,
                 x => x.AccountService.AccountUsersNullable)
-                   .Where(tuple => tuple.Item1.Any() && tuple.Item2.Any())
+                   .Where(tuple => tuple.Item1?.Count > 0 && tuple.Item2?.Count > 0)
                    .Select(tuple =>
                    {
                        var (projects, users) = tuple;
-                       return (int?)users.Values.Count(x => !string.IsNullOrWhiteSpace(x?.LastName));
+                       return users?.Values.Count(x => !string.IsNullOrWhiteSpace(x?.LastName));
                    })
                    .ToProperty(fixture, x => x.AccountsFound, out fixture._accountsFound);
 

src/ReactiveUI.Tests/Resolvers/DependencyResolverTests.cs

@@ -145,13 +145,13 @@ private static Dictionary<Type, List<Type>> GetServicesThatShouldBeRegistered(IR
 
             new Registrations().Register((factory, serviceType) =>
             {
-                if (serviceTypeToImplementationTypes.TryGetValue(serviceType, out var implementationTypes) == false)
+                if (serviceTypeToImplementationTypes.TryGetValue(serviceType!, out var implementationTypes) == false)
                 {
                     implementationTypes = new List<Type>();
-                    serviceTypeToImplementationTypes.Add(serviceType, implementationTypes);
+                    serviceTypeToImplementationTypes.Add(serviceType!, implementationTypes);
                 }
 
-                implementationTypes.Add(factory().GetType());
+                implementationTypes.Add(factory()!.GetType());
             });
 
             new PlatformRegistrations().Register((factory, serviceType) =>

src/ReactiveUI.Tests/WhenAny/Mockups/HostTestFixture.cs

@@ -3,19 +3,50 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
+using System.Reactive.Linq;
+
 namespace ReactiveUI.Tests
 {
     /// <summary>
     /// A host test fixture.
     /// </summary>
     public class HostTestFixture : ReactiveObject
     {
+        private readonly ObservableAsPropertyHelper<string?> _ownerName;
         private TestFixture? _Child;
-
+        private OwnerClass? _owner;
         private NonObservableTestFixture? _PocoChild;
-
         private int _SomeOtherParam;
 
+        public HostTestFixture()
+        {
+            _ownerName = this.WhenAnyValue(x => x.Owner)
+              .WhereNotNull()
+              .Select(owner => owner.WhenAnyValue(x => x.Name))
+              .Switch()
+              .ToProperty(this, x => x.OwnerName);
+        }
+
+        /// <summary>
+        /// Gets the name of the owner.
+        /// </summary>
+        /// <value>
+        /// The name of the owner.
+        /// </value>
+        public string? OwnerName => _ownerName.Value;
+
+        /// <summary>
+        /// Gets or sets the owner.
+        /// </summary>
+        /// <value>
+        /// The owner.
+        /// </value>
+        public OwnerClass? Owner
+        {
+            get => _owner;
+            set => this.RaiseAndSetIfChanged(ref _owner, value);
+        }
+
         /// <summary>
         /// Gets or sets the child.
         /// </summary>

src/ReactiveUI.Tests/WhenAny/Mockups/OwnerClass.cs

@@ -0,0 +1,28 @@
+// Copyright (c) 2021 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+namespace ReactiveUI.Tests
+{
+    /// <summary>
+    /// Owner Class.
+    /// </summary>
+    /// <seealso cref="ReactiveUI.ReactiveObject" />
+    public class OwnerClass : ReactiveObject
+    {
+        private string? _name;
+
+        /// <summary>
+        /// Gets or sets the name.
+        /// </summary>
+        /// <value>
+        /// The name.
+        /// </value>
+        public string? Name
+        {
+            get => _name;
+            set => this.RaiseAndSetIfChanged(ref _name, value);
+        }
+    }
+}

src/ReactiveUI.Tests/WhenAny/ReactiveNotifyPropertyChangedMixinTest.cs

@@ -636,9 +636,9 @@ public void WhenAnyValueShouldWorkEvenWithNormalProperties()
             };
 
             var output1 = new List<string?>();
-            var output2 = new List<int>();
+            var output2 = new List<int?>();
             fixture.WhenAnyValue(x => x.PocoProperty).Subscribe(output1.Add);
-            fixture.WhenAnyValue(x => x.IsOnlyOneWord, x => x.Length).Subscribe(output2.Add);
+            fixture.WhenAnyValue(x => x.IsOnlyOneWord, x => x?.Length).Subscribe(output2.Add);
 
             Assert.Equal(1, output1.Count);
             Assert.Equal("Bamf", output1[0]);
@@ -784,11 +784,11 @@ public void NullableTypesTestShouldntNeedDecorators2()
             fixture.WhenAnyValue(
                 x => x.ProjectService.ProjectsNullable,
                 x => x.AccountService.AccountUsersNullable)
-                   .Where(tuple => tuple.Item1.Any() && tuple.Item2.Any())
+                   .Where(tuple => tuple.Item1?.Count > 0 && tuple.Item2?.Count > 0)
                    .Select(tuple =>
                    {
                        var (projects, users) = tuple;
-                       return users.Values.Where(x => !string.IsNullOrWhiteSpace(x?.LastName));
+                       return users?.Values.Where(x => !string.IsNullOrWhiteSpace(x?.LastName));
                    })
                    .Subscribe(dict => result = dict);
 
@@ -804,7 +804,7 @@ public void NonNullableTypesTestShouldntNeedDecorators()
             WhenAnyTestFixture fixture = new();
             IEnumerable<AccountUser>? result = null;
             fixture.WhenAnyValue(x => x.AccountService.AccountUsers)
-                   .Where(users => users.Any())
+                   .Where(users => users.Count > 0)
                    .Select(users => users.Values.Where(x => !string.IsNullOrWhiteSpace(x.LastName)))
                    .Subscribe(dict => result = dict);
 
@@ -818,15 +818,15 @@ public void NonNullableTypesTestShouldntNeedDecorators()
         public void NonNullableTypesTestShouldntNeedDecorators2()
         {
             WhenAnyTestFixture fixture = new();
-            IEnumerable<AccountUser?>? result = null;
+            IEnumerable<AccountUser>? result = null;
             fixture.WhenAnyValue(
                 x => x.ProjectService.Projects,
                 x => x.AccountService.AccountUsers)
-                   .Where(tuple => tuple.Item1.Any() && tuple.Item2.Any())
+                   .Where(tuple => tuple.Item1?.Count > 0 && tuple.Item2?.Count > 0)
                    .Select(tuple =>
                    {
                        var (projects, users) = tuple;
-                       return users.Values.Where(x => !string.IsNullOrWhiteSpace(x?.LastName));
+                       return users!.Values.Where(x => !string.IsNullOrWhiteSpace(x.LastName));
                    })
                    .Subscribe(dict => result = dict);
 
@@ -842,16 +842,52 @@ public void WhenAnyValueWith1Paramerters()
             WhenAnyTestFixture fixture = new();
             string? result = null;
             fixture.WhenAnyValue(
-                x => x.Value1)
-                   .Select(value =>
-                   {
-                       return value;
-                   })
-                   .Subscribe(value => result = value);
+                x => x.Value1).Subscribe(value => result = value);
 
             Assert.Equal(result, "1");
         }
 
+        [Fact]
+        public void WhenAnyValueWith1ParamertersSequentialCheck()
+        {
+            WhenAnyTestFixture fixture = new();
+            var result = string.Empty;
+            fixture.Value1 = null!;
+            fixture.WhenAnyValue(
+                x => x.Value1).Subscribe(value => result = value);
+
+            Assert.Equal(result, null);
+
+            fixture.Value1 = "A";
+            Assert.Equal(result, "A");
+
+            fixture.Value1 = "B";
+            Assert.Equal(result, "B");
+
+            fixture.Value1 = null!;
+            Assert.Equal(result, null);
+        }
+
+        [Fact]
+        public void WhenAnyValueWith1ParamertersSequentialCheckNullable()
+        {
+            WhenAnyTestFixture fixture = new();
+            var result = string.Empty;
+            fixture.WhenAnyValue(
+                x => x.Value2).Subscribe(value => result = value);
+
+            Assert.Equal(result, null);
+
+            fixture.Value2 = "A";
+            Assert.Equal(result, "A");
+
+            fixture.Value2 = "B";
+            Assert.Equal(result, "B");
+
+            fixture.Value2 = null;
+            Assert.Equal(result, null);
+        }
+
         /// <summary>
         /// Whens any value with2 paramerters returns tuple.
         /// </summary>
@@ -1289,5 +1325,31 @@ public void WhenAnyValueWith12ParamertersReturnsValues()
 
             Assert.Equal(result, "1357911");
         }
+
+        [Fact]
+        public void WhenAnyValueWithToProperty()
+        {
+            HostTestFixture? fixture = new();
+
+            Assert.Equal(null, fixture.Owner);
+            Assert.Equal(null, fixture.OwnerName);
+
+            fixture.Owner = new();
+            fixture.Owner.Name = "Fred";
+            Assert.NotNull(fixture.Owner);
+            Assert.Equal("Fred", fixture.OwnerName);
+
+            fixture.Owner.Name = "Wilma";
+            Assert.Equal("Wilma", fixture.OwnerName);
+
+            fixture.Owner.Name = null;
+            Assert.Equal(null, fixture.OwnerName);
+
+            fixture.Owner.Name = "Barney";
+            Assert.Equal("Barney", fixture.OwnerName);
+
+            fixture.Owner.Name = "Betty";
+            Assert.Equal("Betty", fixture.OwnerName);
+        }
     }
 }

src/ReactiveUI/Mixins/ReactiveNotifyPropertyChangedMixin.cs

@@ -49,15 +49,10 @@ public static class ReactiveNotifyPropertyChangedMixin
         /// notifications for the given property.</returns>
         public static IObservable<IObservedChange<TSender, TValue>> ObservableForProperty<TSender, TValue>(
                 this TSender? item,
-                Expression<Func<TSender, TValue?>> property,
+                Expression<Func<TSender, TValue>> property,
                 bool beforeChange = false,
                 bool skipInitial = true)
         {
-            if (item is null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
-
             if (property is null)
             {
                 throw new ArgumentNullException(nameof(property));
@@ -105,7 +100,7 @@ public static IObservable<IObservedChange<TSender, TValue>> ObservableForPropert
         /// notifications for the given property.</returns>
         public static IObservable<TRet> ObservableForProperty<TSender, TValue, TRet>(
                 this TSender? item,
-                Expression<Func<TSender, TValue?>> property,
+                Expression<Func<TSender, TValue>> property,
                 Func<TValue?, TRet> selector,
                 bool beforeChange = false) // TODO: Create Test
             where TSender : class
@@ -139,13 +134,8 @@ public static IObservable<IObservedChange<TSender, TValue>> SubscribeToExpressio
             bool skipInitial = true,
             bool suppressWarnings = false) // TODO: Create Test
         {
-            if (source is null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
-
             IObservable<IObservedChange<object?, object?>> notifier =
-                Observable.Return(new ObservedChange<object?, object?>(null, null!, source));
+                Observable.Return(new ObservedChange<object?, object?>(null, null, source));
 
             var chain = Reflection.Rewrite(expression).GetExpressionChain();
             notifier = chain.Aggregate(notifier, (n, expr) => n
@@ -168,7 +158,7 @@ public static IObservable<IObservedChange<TSender, TValue>> SubscribeToExpressio
                     throw new InvalidCastException($"Unable to cast from {val.GetType()} to {typeof(TValue)}.");
                 }
 
-                return new ObservedChange<TSender, TValue>(source, expression, (TValue)val!);
+                return new ObservedChange<TSender, TValue>(source!, expression, (TValue)val!);
             });
 
             return r.DistinctUntilChanged(x => x.Value);