feature: Add C# 8 Nullability

.gitignore

@@ -365,4 +365,5 @@ src/Tools/
 **/*.Android/**/[Rr]esource.[Dd]esigner.cs
 **/*.Droid/**/[Rr]esource.[Dd]esigner.cs
 **/Android/**/[Rr]esource.[Dd]esigner.cs
-**/Droid/**/[Rr]esource.[Dd]esigner.cs
+**/Droid/**/[Rr]esource.[Dd]esigner.cs
+**/[Rr]esources/[Rr]esource.[Dd]esigner.cs

src/Directory.build.props

@@ -29,6 +29,9 @@
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <!-- Include PDB in the built .nupkg -->
     <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
+    <Nullable>enable</Nullable>
+    <LangVersion>latest</LangVersion>
+    <WarningsAsErrors>CS8600;CS8602;CS8603;CS8604;CS8605;CS8606;CS8607;CS8608;CS8609;CS8610;CS8611;CS8612;CS8613;CS8614;CS8615;CS8616;CS8617;CS8618;CS8619;CS8620;CS8621;CS8622;CS8623;CS8624;CS8625;CS8626;CS8627;CS8628;CS8629;CS8630;CS8634;CS8766;CS8767</WarningsAsErrors>
   </PropertyGroup>
 
   <!-- MonoAndroid doesn't seem to want to allow debugging for maintainers -->

src/ReactiveUI.AndroidSupport/ReactiveAppCompatActivity.cs

@@ -27,7 +27,7 @@ namespace ReactiveUI.AndroidSupport
     public class ReactiveAppCompatActivity<TViewModel> : ReactiveAppCompatActivity, IViewFor<TViewModel>, ICanActivate
         where TViewModel : class
     {
-        private TViewModel _viewModel;
+        private TViewModel? _viewModel;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReactiveAppCompatActivity{TViewModel}"/> class.
@@ -37,17 +37,17 @@ protected ReactiveAppCompatActivity()
         }
 
         /// <inheritdoc/>
-        public TViewModel ViewModel
+        public TViewModel? ViewModel
         {
             get => _viewModel;
             set => this.RaiseAndSetIfChanged(ref _viewModel, value);
         }
 
         /// <inheritdoc/>
-        object IViewFor.ViewModel
+        object? IViewFor.ViewModel
         {
             get => _viewModel;
-            set => _viewModel = (TViewModel)value;
+            set => _viewModel = (TViewModel?)value;
         }
     }
 
@@ -80,10 +80,10 @@ protected ReactiveAppCompatActivity(IntPtr handle, JniHandleOwnership ownership)
         }
 
         /// <inheritdoc/>
-        public event PropertyChangingEventHandler PropertyChanging;
+        public event PropertyChangingEventHandler? PropertyChanging;
 
         /// <inheritdoc/>
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler? PropertyChanged;
 
         /// <inheritdoc/>
         public IObservable<IReactivePropertyChangedEventArgs<ReactiveAppCompatActivity>> Changing => this.GetChangingObservable();

src/ReactiveUI.AndroidSupport/ReactiveDialogFragment.cs

@@ -21,7 +21,7 @@ namespace ReactiveUI.AndroidSupport
     public class ReactiveDialogFragment<TViewModel> : ReactiveDialogFragment, IViewFor<TViewModel>, ICanActivate
         where TViewModel : class
     {
-        private TViewModel _viewModel;
+        private TViewModel? _viewModel;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReactiveDialogFragment{TViewModel}"/> class.
@@ -31,17 +31,17 @@ protected ReactiveDialogFragment()
         }
 
         /// <inheritdoc/>
-        public TViewModel ViewModel
+        public TViewModel? ViewModel
         {
             get => _viewModel;
             set => this.RaiseAndSetIfChanged(ref _viewModel, value);
         }
 
         /// <inheritdoc/>
-        object IViewFor.ViewModel
+        object? IViewFor.ViewModel
         {
             get => _viewModel;
-            set => _viewModel = (TViewModel)value;
+            set => _viewModel = (TViewModel?)value;
         }
     }
 
@@ -63,10 +63,10 @@ protected ReactiveDialogFragment()
         }
 
         /// <inheritdoc/>
-        public event PropertyChangingEventHandler PropertyChanging;
+        public event PropertyChangingEventHandler? PropertyChanging;
 
         /// <inheritdoc/>
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler? PropertyChanged;
 
         /// <inheritdoc/>
         public IObservable<Exception> ThrownExceptions => this.GetThrownExceptionsObservable();

src/ReactiveUI.AndroidSupport/ReactiveFragment.cs

@@ -21,7 +21,7 @@ namespace ReactiveUI.AndroidSupport
     public class ReactiveFragment<TViewModel> : ReactiveFragment, IViewFor<TViewModel>, ICanActivate
         where TViewModel : class
     {
-        private TViewModel _viewModel;
+        private TViewModel? _viewModel;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReactiveFragment{TViewModel}"/> class.
@@ -31,17 +31,17 @@ protected ReactiveFragment()
         }
 
         /// <inheritdoc/>
-        public TViewModel ViewModel
+        public TViewModel? ViewModel
         {
             get => _viewModel;
             set => this.RaiseAndSetIfChanged(ref _viewModel, value);
         }
 
         /// <inheritdoc/>
-        object IViewFor.ViewModel
+        object? IViewFor.ViewModel
         {
             get => _viewModel;
-            set => _viewModel = (TViewModel)value;
+            set => _viewModel = (TViewModel?)value;
         }
     }
 
@@ -63,10 +63,10 @@ protected ReactiveFragment()
         }
 
         /// <inheritdoc/>
-        public event PropertyChangingEventHandler PropertyChanging;
+        public event PropertyChangingEventHandler? PropertyChanging;
 
         /// <inheritdoc/>
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler? PropertyChanged;
 
         /// <inheritdoc/>
         public IObservable<Exception> ThrownExceptions => this.GetThrownExceptionsObservable();

src/ReactiveUI.AndroidSupport/ReactiveFragmentActivity.cs

@@ -27,7 +27,7 @@ namespace ReactiveUI.AndroidSupport
     public class ReactiveFragmentActivity<TViewModel> : ReactiveFragmentActivity, IViewFor<TViewModel>, ICanActivate
         where TViewModel : class
     {
-        private TViewModel _viewModel;
+        private TViewModel? _viewModel;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReactiveFragmentActivity{TViewModel}"/> class.
@@ -37,17 +37,17 @@ protected ReactiveFragmentActivity()
         }
 
         /// <inheritdoc/>
-        public TViewModel ViewModel
+        public TViewModel? ViewModel
         {
             get => _viewModel;
             set => this.RaiseAndSetIfChanged(ref _viewModel, value);
         }
 
         /// <inheritdoc/>
-        object IViewFor.ViewModel
+        object? IViewFor.ViewModel
         {
             get => _viewModel;
-            set => _viewModel = (TViewModel)value;
+            set => _viewModel = (TViewModel?)value;
         }
     }
 
@@ -63,10 +63,10 @@ public class ReactiveFragmentActivity : FragmentActivity, IReactiveObject, IReac
         private readonly Subject<(int requestCode, Result result, Intent intent)> _activityResult = new Subject<(int requestCode, Result result, Intent intent)>();
 
         /// <inheritdoc/>
-        public event PropertyChangingEventHandler PropertyChanging;
+        public event PropertyChangingEventHandler? PropertyChanging;
 
         /// <inheritdoc/>
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler? PropertyChanged;
 
         /// <inheritdoc />
         public IObservable<IReactivePropertyChangedEventArgs<ReactiveFragmentActivity>> Changing => this.GetChangingObservable();
@@ -78,7 +78,7 @@ public class ReactiveFragmentActivity : FragmentActivity, IReactiveObject, IReac
         public IObservable<Exception> ThrownExceptions => this.GetThrownExceptionsObservable();
 
         /// <summary>
-        /// Gets a singal when the activity fragment is activated.
+        /// Gets a signal when the activity fragment is activated.
         /// </summary>
         public IObservable<Unit> Activated => _activated.AsObservable();
 

src/ReactiveUI.AndroidSupport/ReactivePagerAdapter.cs

@@ -28,7 +28,7 @@ public class ReactivePagerAdapter<TViewModel> : PagerAdapter, IEnableLogger
     {
         private readonly SourceList<TViewModel> _list;
         private readonly Func<TViewModel, ViewGroup, View> _viewCreator;
-        private readonly Action<TViewModel, View> _viewInitializer;
+        private readonly Action<TViewModel, View>? _viewInitializer;
         private readonly IDisposable _inner;
 
         /// <summary>
@@ -40,7 +40,7 @@ public class ReactivePagerAdapter<TViewModel> : PagerAdapter, IEnableLogger
         public ReactivePagerAdapter(
             IObservable<IChangeSet<TViewModel>> changeSet,
             Func<TViewModel, ViewGroup, View> viewCreator,
-            Action<TViewModel, View> viewInitializer = null)
+            Action<TViewModel, View>? viewInitializer = null)
         {
             _list = new SourceList<TViewModel>(changeSet);
             _viewCreator = viewCreator;
@@ -132,7 +132,7 @@ public class ReactivePagerAdapter<TViewModel, TCollection> : ReactivePagerAdapte
         public ReactivePagerAdapter(
             TCollection collection,
             Func<TViewModel, ViewGroup, View> viewCreator,
-            Action<TViewModel, View> viewInitializer = null)
+            Action<TViewModel, View>? viewInitializer = null)
             : base(collection.ToObservableChangeSet<TCollection, TViewModel>(), viewCreator, viewInitializer)
         {
         }

src/ReactiveUI.AndroidSupport/ReactivePreferenceFragment.cs

@@ -23,7 +23,7 @@ namespace ReactiveUI.AndroidSupport
     public abstract class ReactivePreferenceFragment<TViewModel> : ReactivePreferenceFragment, IViewFor<TViewModel>, ICanActivate
         where TViewModel : class
     {
-        private TViewModel _viewModel;
+        private TViewModel? _viewModel;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReactivePreferenceFragment{TViewModel}"/> class.
@@ -43,17 +43,17 @@ protected ReactivePreferenceFragment(IntPtr handle, JniHandleOwnership ownership
         }
 
         /// <inheritdoc/>
-        public TViewModel ViewModel
+        public TViewModel? ViewModel
         {
             get => _viewModel;
             set => this.RaiseAndSetIfChanged(ref _viewModel, value);
         }
 
         /// <inheritdoc/>
-        object IViewFor.ViewModel
+        object? IViewFor.ViewModel
         {
             get => _viewModel;
-            set => _viewModel = (TViewModel)value;
+            set => _viewModel = (TViewModel?)value;
         }
     }
 
@@ -85,10 +85,10 @@ protected ReactivePreferenceFragment(IntPtr handle, JniHandleOwnership ownership
         }
 
         /// <inheritdoc/>
-        public event PropertyChangingEventHandler PropertyChanging;
+        public event PropertyChangingEventHandler? PropertyChanging;
 
         /// <inheritdoc/>
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler? PropertyChanged;
 
         /// <inheritdoc />
         public IObservable<IReactivePropertyChangedEventArgs<ReactivePreferenceFragment>> Changing => this.GetChangingObservable();

src/ReactiveUI.AndroidSupport/ReactiveRecyclerViewAdapter.cs

@@ -60,7 +60,7 @@ public override int GetItemViewType(int position)
         /// <param name="position">The position of the current view in the list.</param>
         /// <param name="viewModel">The ViewModel associated with the current View.</param>
         /// <returns>An ID to be used in OnCreateViewHolder.</returns>
-        public virtual int GetItemViewType(int position, TViewModel viewModel)
+        public virtual int GetItemViewType(int position, TViewModel? viewModel)
         {
             return base.GetItemViewType(position);
         }
@@ -93,7 +93,7 @@ protected override void Dispose(bool disposing)
             base.Dispose(disposing);
         }
 
-        private TViewModel GetViewModelByPosition(int position)
+        private TViewModel? GetViewModelByPosition(int position)
         {
             return position >= _list.Count ? null : _list.Items.ElementAt(position);
         }

src/ReactiveUI.AndroidSupport/ReactiveRecyclerViewViewHolder.cs

@@ -29,9 +29,9 @@ public class ReactiveRecyclerViewViewHolder<TViewModel> : RecyclerView.ViewHolde
         [SuppressMessage("Design", "CA1051: Do not declare visible instance fields", Justification = "Legacy reasons")]
         [SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1306: Field should start with a lower case letter", Justification = "Legacy reasons")]
         [IgnoreDataMember]
-        protected Lazy<PropertyInfo[]> AllPublicProperties;
+        protected Lazy<PropertyInfo[]> AllPublicProperties = null!;
 
-        private TViewModel _viewModel;
+        private TViewModel? _viewModel;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReactiveRecyclerViewViewHolder{TViewModel}"/> class.
@@ -60,7 +60,7 @@ protected ReactiveRecyclerViewViewHolder(View view)
                                 h => view.LongClick += h,
                                 h => view.LongClick -= h);
 
-            SelectedWithViewModel = Observable.FromEvent<EventHandler, TViewModel>(
+            SelectedWithViewModel = Observable.FromEvent<EventHandler, TViewModel?>(
                                 eventHandler =>
                                 {
                                     void Handler(object sender, EventArgs e) => eventHandler(ViewModel);
@@ -69,7 +69,7 @@ protected ReactiveRecyclerViewViewHolder(View view)
                                 h => view.Click += h,
                                 h => view.Click -= h);
 
-            LongClickedWithViewModel = Observable.FromEvent<EventHandler<View.LongClickEventArgs>, TViewModel>(
+            LongClickedWithViewModel = Observable.FromEvent<EventHandler<View.LongClickEventArgs>, TViewModel?>(
                                 eventHandler =>
                                 {
                                     void Handler(object sender, View.LongClickEventArgs e) => eventHandler(ViewModel);
@@ -80,10 +80,10 @@ protected ReactiveRecyclerViewViewHolder(View view)
         }
 
         /// <inheritdoc/>
-        public event PropertyChangingEventHandler PropertyChanging;
+        public event PropertyChangingEventHandler PropertyChanging = null!;
 
         /// <inheritdoc/>
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler PropertyChanged = null!;
 
         /// <summary>
         /// Gets an observable that signals that this ViewHolder has been selected.
@@ -98,7 +98,7 @@ protected ReactiveRecyclerViewViewHolder(View view)
         ///
         /// The <see cref="IObservable{TViewModel}"/> is the ViewModel of this ViewHolder in the <see cref="RecyclerView"/>.
         /// </summary>
-        public IObservable<TViewModel> SelectedWithViewModel { get; }
+        public IObservable<TViewModel?> SelectedWithViewModel { get; }
 
         /// <summary>
         /// Gets an observable that signals that this ViewHolder has been long-clicked.
@@ -113,15 +113,15 @@ protected ReactiveRecyclerViewViewHolder(View view)
         ///
         /// The <see cref="IObservable{TViewModel}"/> is the ViewModel of this ViewHolder in the <see cref="RecyclerView"/>.
         /// </summary>
-        public IObservable<TViewModel> LongClickedWithViewModel { get; }
+        public IObservable<TViewModel?> LongClickedWithViewModel { get; }
 
         /// <summary>
         /// Gets the current view being shown.
         /// </summary>
         public View View => ItemView;
 
         /// <inheritdoc/>
-        public TViewModel ViewModel
+        public TViewModel? ViewModel
         {
             get => _viewModel;
             set => this.RaiseAndSetIfChanged(ref _viewModel, value);
@@ -134,10 +134,10 @@ public TViewModel ViewModel
         public IObservable<Exception> ThrownExceptions => this.GetThrownExceptionsObservable();
 
         /// <inheritdoc/>
-        object IViewFor.ViewModel
+        object? IViewFor.ViewModel
         {
             get => ViewModel;
-            set => ViewModel = (TViewModel)value;
+            set => ViewModel = (TViewModel?)value;
         }
 
         /// <inheritdoc/>

src/ReactiveUI.AndroidSupport/ReactiveUI.AndroidSupport.csproj

@@ -4,6 +4,7 @@
     <TargetFrameworks>MonoAndroid90</TargetFrameworks>
     <PackageDescription>Provides ReactiveUI extensions for the Android Support Library</PackageDescription>
     <PackageId>ReactiveUI.AndroidSupport</PackageId>
+    <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <PackageTags>mvvm;reactiveui;rx;reactive extensions;observable;LINQ;events;frp;xamarin;android;forms;monodroid;monotouch;xamarin.android;net;</PackageTags>
   </PropertyGroup>