Merge pull request #7240 from AvaloniaUI/fixes/avalonia-styling-nulla…

…bility

Added nullable annotations to Avalonia.Styling.

src/Avalonia.Styling/Avalonia.Styling.csproj

@@ -9,4 +9,5 @@
     <ProjectReference Include="..\Avalonia.Base\Avalonia.Base.csproj" />
   </ItemGroup>
   <Import Project="..\..\build\ApiDiff.props" />
+  <Import Project="..\..\build\NullableEnable.props" />
 </Project>

src/Avalonia.Styling/Controls/ChildNameScope.cs

@@ -15,20 +15,20 @@ public ChildNameScope(INameScope parentScope)
 
         public void Register(string name, object element) => _inner.Register(name, element);
 
-        public SynchronousCompletionAsyncResult<object> FindAsync(string name)
+        public SynchronousCompletionAsyncResult<object?> FindAsync(string name)
         {
             var found = Find(name);
             if (found != null)
-                return new SynchronousCompletionAsyncResult<object>(found);
+                return new SynchronousCompletionAsyncResult<object?>(found);
             // Not found and both current and parent scope are in completed state
             if(IsCompleted)
-                return new SynchronousCompletionAsyncResult<object>(null);
+                return new SynchronousCompletionAsyncResult<object?>(null);
             return DoFindAsync(name);
         }
 
-        public SynchronousCompletionAsyncResult<object> DoFindAsync(string name)
+        public SynchronousCompletionAsyncResult<object?> DoFindAsync(string name)
         {
-            var src = new SynchronousCompletionAsyncResultSource<object>();
+            var src = new SynchronousCompletionAsyncResultSource<object?>();
 
             void ParentSearch()
             {
@@ -56,7 +56,7 @@ void ParentSearch()
             return src.AsyncResult;
         }
 
-        public object Find(string name)
+        public object? Find(string name)
         {
             var found = _inner.Find(name);
             if (found != null)

src/Avalonia.Styling/Controls/INameScope.cs

@@ -22,14 +22,14 @@ public interface INameScope
         /// </summary>
         /// <param name="name">The name.</param>
         /// <returns>The element, or null if the name was not found.</returns>
-        SynchronousCompletionAsyncResult<object> FindAsync(string name);
+        SynchronousCompletionAsyncResult<object?> FindAsync(string name);
 
         /// <summary>
         /// Finds a named element in the name scope, returns immediately, doesn't traverse the name scope stack
         /// </summary>
         /// <param name="name">The name.</param>
         /// <returns>The element, or null if the name was not found.</returns>
-        object Find(string name);
+        object? Find(string name);
 
         /// <summary>
         /// Marks the name scope as completed, no further registrations will be allowed

src/Avalonia.Styling/Controls/NameScope.cs

@@ -22,8 +22,8 @@ public class NameScope : INameScope
 
         private readonly Dictionary<string, object> _inner = new Dictionary<string, object>();
 
-        private readonly Dictionary<string, SynchronousCompletionAsyncResultSource<object>> _pendingSearches =
-            new Dictionary<string, SynchronousCompletionAsyncResultSource<object>>();
+        private readonly Dictionary<string, SynchronousCompletionAsyncResultSource<object?>> _pendingSearches =
+            new Dictionary<string, SynchronousCompletionAsyncResultSource<object?>>();
 
         /// <summary>
         /// Gets the value of the attached <see cref="NameScopeProperty"/> on a styled element.
@@ -32,7 +32,7 @@ public class NameScope : INameScope
         /// <returns>The value of the NameScope attached property.</returns>
         public static INameScope GetNameScope(StyledElement styled)
         {
-            Contract.Requires<ArgumentNullException>(styled != null);
+            _ = styled ?? throw new ArgumentNullException(nameof(styled));
 
             return styled.GetValue(NameScopeProperty);
         }
@@ -44,7 +44,7 @@ public static INameScope GetNameScope(StyledElement styled)
         /// <param name="value">The value to set.</param>
         public static void SetNameScope(StyledElement styled, INameScope value)
         {
-            Contract.Requires<ArgumentNullException>(styled != null);
+            _ = styled ?? throw new ArgumentNullException(nameof(styled));
 
             styled.SetValue(NameScopeProperty, value);
         }
@@ -54,12 +54,11 @@ public void Register(string name, object element)
         {
             if (IsCompleted)
                 throw new InvalidOperationException("NameScope is completed, no further registrations are allowed");
-            Contract.Requires<ArgumentNullException>(name != null);
-            Contract.Requires<ArgumentNullException>(element != null);
 
-            object existing;
+            _ = name ?? throw new ArgumentNullException(nameof(name));
+            _ = element ?? throw new ArgumentNullException(nameof(element));
 
-            if (_inner.TryGetValue(name, out existing))
+            if (_inner.TryGetValue(name, out var existing))
             {
                 if (existing != element)
                 {
@@ -77,27 +76,26 @@ public void Register(string name, object element)
             }
         }
 
-        public SynchronousCompletionAsyncResult<object> FindAsync(string name)
+        public SynchronousCompletionAsyncResult<object?> FindAsync(string name)
         {
             var found = Find(name);
             if (found != null)
-                return new SynchronousCompletionAsyncResult<object>(found);
+                return new SynchronousCompletionAsyncResult<object?>(found);
             if (IsCompleted)
-                return new SynchronousCompletionAsyncResult<object>((object)null);
+                return new SynchronousCompletionAsyncResult<object?>(null);
             if (!_pendingSearches.TryGetValue(name, out var tcs))
                 // We are intentionally running continuations synchronously here
-                _pendingSearches[name] = tcs = new SynchronousCompletionAsyncResultSource<object>();
+                _pendingSearches[name] = tcs = new SynchronousCompletionAsyncResultSource<object?>();
 
             return tcs.AsyncResult;
         }
 
         /// <inheritdoc />
-        public object Find(string name)
+        public object? Find(string name)
         {
-            Contract.Requires<ArgumentNullException>(name != null);
+            _ = name ?? throw new ArgumentNullException(nameof(name));
 
-            object result;
-            _inner.TryGetValue(name, out result);
+            _inner.TryGetValue(name, out var result);
             return result;
         }
 

src/Avalonia.Styling/Controls/NameScopeExtensions.cs

@@ -17,11 +17,11 @@ public static class NameScopeExtensions
         /// <param name="nameScope">The name scope.</param>
         /// <param name="name">The name.</param>
         /// <returns>The named element or null if not found.</returns>
-        public static T Find<T>(this INameScope nameScope, string name)
+        public static T? Find<T>(this INameScope nameScope, string name)
             where T : class
         {
-            Contract.Requires<ArgumentNullException>(nameScope != null);
-            Contract.Requires<ArgumentNullException>(name != null);
+            _ = nameScope ?? throw new ArgumentNullException(nameof(nameScope));
+            _ = name ?? throw new ArgumentNullException(nameof(name));
 
             var result = nameScope.Find(name);
 
@@ -31,7 +31,7 @@ public static T Find<T>(this INameScope nameScope, string name)
                     $"Expected control '{name}' to be '{typeof(T)} but it was '{result.GetType()}'.");
             }
 
-            return (T)result;
+            return (T?)result;
         }
 
         /// <summary>
@@ -41,11 +41,11 @@ public static T Find<T>(this INameScope nameScope, string name)
         /// <param name="anchor">The control to take the name scope from.</param>
         /// <param name="name">The name.</param>
         /// <returns>The named element or null if not found.</returns>
-        public static T Find<T>(this ILogical anchor, string name)
+        public static T? Find<T>(this ILogical anchor, string name)
             where T : class
         {
-            Contract.Requires<ArgumentNullException>(anchor != null);
-            Contract.Requires<ArgumentNullException>(name != null);
+            _ = anchor ?? throw new ArgumentNullException(nameof(anchor));
+            _ = name ?? throw new ArgumentNullException(nameof(name));
             var styledAnchor = anchor as StyledElement;
             if (styledAnchor == null)
                 return null;
@@ -64,8 +64,8 @@ public static T Find<T>(this ILogical anchor, string name)
         public static T Get<T>(this INameScope nameScope, string name)
             where T : class
         {
-            Contract.Requires<ArgumentNullException>(nameScope != null);
-            Contract.Requires<ArgumentNullException>(name != null);
+            _ = nameScope ?? throw new ArgumentNullException(nameof(nameScope));
+            _ = name ?? throw new ArgumentNullException(nameof(name));
 
             var result = nameScope.Find(name);
 
@@ -94,9 +94,9 @@ public static T Get<T>(this INameScope nameScope, string name)
         public static T Get<T>(this ILogical anchor, string name)
             where T : class
         {
-            Contract.Requires<ArgumentNullException>(anchor != null);
-            Contract.Requires<ArgumentNullException>(name != null);
-               
+            _ = anchor ?? throw new ArgumentNullException(nameof(anchor));
+            _ = name ?? throw new ArgumentNullException(nameof(name));
+
             var nameScope = (anchor as INameScope) ?? NameScope.GetNameScope((StyledElement)anchor);
             if (nameScope == null)
                 throw new InvalidOperationException(
@@ -105,9 +105,9 @@ public static T Get<T>(this ILogical anchor, string name)
             return nameScope.Get<T>(name);
         }
 
-        public static INameScope FindNameScope(this ILogical control)
+        public static INameScope? FindNameScope(this ILogical control)
         {
-            Contract.Requires<ArgumentNullException>(control != null);
+            _ = control ?? throw new ArgumentNullException(nameof(control));
 
             var scope = control.GetSelfAndLogicalAncestors()
                 .OfType<StyledElement>()

src/Avalonia.Styling/Controls/NameScopeLocator.cs

@@ -11,9 +11,9 @@ public class NameScopeLocator
         /// </summary>
         /// <param name="scope">The scope relative from which the object should be resolved.</param>
         /// <param name="name">The name of the object to find.</param>
-        public static IObservable<object> Track(INameScope scope, string name)
+        public static IObservable<object?> Track(INameScope scope, string name)
         {
-            return new NeverEndingSynchronousCompletionAsyncResultObservable<object>(scope.FindAsync(name));
+            return new NeverEndingSynchronousCompletionAsyncResultObservable<object?>(scope.FindAsync(name));
         }
 
         // This class is implemented in such weird way because for some reason
@@ -22,7 +22,7 @@ public static IObservable<object> Track(INameScope scope, string name)
 
         private class NeverEndingSynchronousCompletionAsyncResultObservable<T> : IObservable<T>
         {
-            private T _value;
+            private T? _value;
             private SynchronousCompletionAsyncResult<T>? _asyncResult;
 
             public NeverEndingSynchronousCompletionAsyncResultObservable(SynchronousCompletionAsyncResult<T> task)
@@ -47,7 +47,7 @@ public IDisposable Subscribe(IObserver<T> observer)
                         observer.OnNext(_asyncResult.Value.GetResult());
                     });
                 else
-                    observer.OnNext(_value);
+                    observer.OnNext(_value!);
 
                 return Disposable.Empty;
             }

src/Avalonia.Styling/Controls/PseudoClassesExtensions.cs

@@ -12,7 +12,7 @@ public static class PseudolassesExtensions
         /// <param name="value">True to add the pseudoclass or false to remove.</param>
         public static void Set(this IPseudoClasses classes, string name, bool value)
         {
-            Contract.Requires<ArgumentNullException>(classes != null);
+            _ = classes ?? throw new ArgumentNullException(nameof(classes));
 
             if (value)
             {

src/Avalonia.Styling/Controls/ResourceDictionary.cs

@@ -177,7 +177,7 @@ void IResourceProvider.RemoveOwner(IResourceHost owner)
             }
         }
 
-        private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        private void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
             Owner?.NotifyHostedResourcesChanged(ResourcesChangedEventArgs.Empty);
         }

src/Avalonia.Styling/Controls/ResourceNodeExtensions.cs

@@ -109,7 +109,7 @@ protected override void Subscribed(IObserver<object?> observer, bool first)
                 observer.OnNext(Convert(_target.FindResource(_key)));
             }
 
-            private void ResourcesChanged(object sender, ResourcesChangedEventArgs e)
+            private void ResourcesChanged(object? sender, ResourcesChangedEventArgs e)
             {
                 PublishNext(Convert(_target.FindResource(_key)));
             }
@@ -159,7 +159,7 @@ private void PublishNext()
                 }
             }
 
-            private void OwnerChanged(object sender, EventArgs e)
+            private void OwnerChanged(object? sender, EventArgs e)
             {
                 if (_owner is object)
                 {
@@ -176,7 +176,7 @@ private void OwnerChanged(object sender, EventArgs e)
                 PublishNext();
             }
 
-            private void ResourcesChanged(object sender, ResourcesChangedEventArgs e)
+            private void ResourcesChanged(object? sender, ResourcesChangedEventArgs e)
             {
                 PublishNext();
             }

src/Avalonia.Styling/INamed.cs

@@ -8,6 +8,6 @@ public interface INamed
         /// <summary>
         /// Gets the element name.
         /// </summary>
-        string Name { get; }
+        string? Name { get; }
     }
 }

src/Avalonia.Styling/LogicalTree/ControlLocator.cs

@@ -9,19 +9,19 @@ namespace Avalonia.LogicalTree
     /// </summary>
     public static class ControlLocator
     {
-        public static IObservable<ILogical> Track(ILogical relativeTo, int ancestorLevel, Type ancestorType = null)
+        public static IObservable<ILogical?> Track(ILogical relativeTo, int ancestorLevel, Type? ancestorType = null)
         {
             return new ControlTracker(relativeTo, ancestorLevel, ancestorType);
         }
 
-        private class ControlTracker : LightweightObservableBase<ILogical>
+        private class ControlTracker : LightweightObservableBase<ILogical?>
         {
             private readonly ILogical _relativeTo;
             private readonly int _ancestorLevel;
-            private readonly Type _ancestorType;
-            private ILogical _value;
+            private readonly Type? _ancestorType;
+            private ILogical? _value;
 
-            public ControlTracker(ILogical relativeTo, int ancestorLevel, Type ancestorType)
+            public ControlTracker(ILogical relativeTo, int ancestorLevel, Type? ancestorType)
             {
                 _relativeTo = relativeTo;
                 _ancestorLevel = ancestorLevel;
@@ -43,18 +43,18 @@ protected override void Deinitialize()
                 _value = null;
             }
 
-            protected override void Subscribed(IObserver<ILogical> observer, bool first)
+            protected override void Subscribed(IObserver<ILogical?> observer, bool first)
             {
                 observer.OnNext(_value);
             }
 
-            private void Attached(object sender, LogicalTreeAttachmentEventArgs e)
+            private void Attached(object? sender, LogicalTreeAttachmentEventArgs e)
             {
                 Update();
                 PublishNext(_value);
             }
 
-            private void Detached(object sender, LogicalTreeAttachmentEventArgs e)
+            private void Detached(object? sender, LogicalTreeAttachmentEventArgs e)
             {
                 _value = null;
                 PublishNext(null);

src/Avalonia.Styling/LogicalTree/ILogical.cs

@@ -12,12 +12,12 @@ public interface ILogical
         /// <summary>
         /// Raised when the control is attached to a rooted logical tree.
         /// </summary>
-        event EventHandler<LogicalTreeAttachmentEventArgs> AttachedToLogicalTree;
+        event EventHandler<LogicalTreeAttachmentEventArgs>? AttachedToLogicalTree;
 
         /// <summary>
         /// Raised when the control is detached from a rooted logical tree.
         /// </summary>
-        event EventHandler<LogicalTreeAttachmentEventArgs> DetachedFromLogicalTree;
+        event EventHandler<LogicalTreeAttachmentEventArgs>? DetachedFromLogicalTree;
 
         /// <summary>
         /// Gets a value indicating whether the element is attached to a rooted logical tree.
@@ -27,7 +27,7 @@ public interface ILogical
         /// <summary>
         /// Gets the logical parent.
         /// </summary>
-        ILogical LogicalParent { get; }
+        ILogical? LogicalParent { get; }
 
         /// <summary>
         /// Gets the logical children.