Nullability annotations for bindables

osu.Framework.Tests/Bindables/BindableDoubleTest.cs

@@ -125,7 +125,7 @@ public void TestParsingNumberLocale(double value, string locale, string expected
             CultureInfo.CurrentCulture = CultureInfo.GetCultureInfo(locale);
 
             var bindable = new BindableDouble(value);
-            string? asString = bindable.ToString();
+            string asString = bindable.ToString();
             Assert.AreEqual(expected, asString);
             Assert.DoesNotThrow(() => bindable.Parse(asString, CultureInfo.CurrentCulture));
             Assert.AreEqual(value, bindable.Value, Precision.DOUBLE_EPSILON);

osu.Framework.Tests/Bindables/BindableFloatTest.cs

@@ -112,7 +112,7 @@ public void TestParsingNumberLocale(float value, string locale, string expected)
             CultureInfo.CurrentCulture = CultureInfo.GetCultureInfo(locale);
 
             var bindable = new BindableFloat(value);
-            string? asString = bindable.ToString();
+            string asString = bindable.ToString();
             Assert.AreEqual(expected, asString);
             Assert.DoesNotThrow(() => bindable.Parse(asString, CultureInfo.CurrentCulture));
             Assert.AreEqual(value, bindable.Value, Precision.FLOAT_EPSILON);

osu.Framework.Tests/Bindables/BindableLeasingTest.cs

@@ -95,7 +95,7 @@ public void TestDoubleLeaseFails()
         public void TestIncorrectEndLease()
         {
             // end a lease when no lease exists.
-            Assert.Throws<InvalidOperationException>(() => original.EndLease(null));
+            Assert.Throws<InvalidOperationException>(() => original.EndLease(null!));
 
             // end a lease with an incorrect bindable
             original.BeginLease(true);

osu.Framework.Tests/Visual/Platform/FrameworkConfigVisualiser.cs

@@ -59,6 +59,6 @@
             }));
         }
 
-        private void updateText() => valueText.Text = bindable.ToString() ?? "<null>";
+        private void updateText() => valueText.Text = bindable?.ToString() ?? "<null>";
     }
 }

osu.Framework/Bindables/AggregateBindable.cs

@@ -1,8 +1,6 @@
 // Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 
@@ -30,7 +28,7 @@ public class AggregateBindable<T>
         /// </summary>
         /// <param name="aggregateFunction">The function to be used for aggregation, taking two input <typeparamref name="T"/> values and returning one output.</param>
         /// <param name="resultBindable">An optional newly constructed bindable to use for <see cref="Result"/>. The initial value of this bindable is used as the initial value for the aggregate.</param>
-        public AggregateBindable(Func<T, T, T> aggregateFunction, Bindable<T> resultBindable = null)
+        public AggregateBindable(Func<T, T, T> aggregateFunction, Bindable<T>? resultBindable = null)
         {
             this.aggregateFunction = aggregateFunction;
             result = resultBindable ?? new Bindable<T>();
@@ -85,7 +83,7 @@ public void RemoveSource(IBindable<T> bindable)
             return null;
         }
 
-        private void recalculateAggregate(ValueChangedEvent<T> obj = null)
+        private void recalculateAggregate(ValueChangedEvent<T>? obj = null)
         {
             T calculated = initialValue;
 

osu.Framework/Bindables/Bindable.cs

@@ -1,10 +1,9 @@
 // Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Linq;
 using JetBrains.Annotations;
@@ -25,20 +24,17 @@ public class Bindable<T> : IBindable<T>, IBindable, IParseable, ISerializableBin
         /// <summary>
         /// An event which is raised when <see cref="Value"/> has changed (or manually via <see cref="TriggerValueChange"/>).
         /// </summary>
-        [CanBeNull]
-        public event Action<ValueChangedEvent<T>> ValueChanged;
+        public event Action<ValueChangedEvent<T>>? ValueChanged;
 
         /// <summary>
         /// An event which is raised when <see cref="Disabled"/> has changed (or manually via <see cref="TriggerDisabledChange"/>).
         /// </summary>
-        [CanBeNull]
-        public event Action<bool> DisabledChanged;
+        public event Action<bool>? DisabledChanged;
 
         /// <summary>
         /// An event which is raised when <see cref="Default"/> has changed (or manually via <see cref="TriggerDefaultChange"/>).
         /// </summary>
-        [CanBeNull]
-        public event Action<ValueChangedEvent<T>> DefaultChanged;
+        public event Action<ValueChangedEvent<T>>? DefaultChanged;
 
         private T value;
 
@@ -63,7 +59,7 @@ public virtual bool Disabled
             }
         }
 
-        internal void SetDisabled(bool value, bool bypassChecks = false, Bindable<T> source = null)
+        internal void SetDisabled(bool value, bool bypassChecks = false, Bindable<T>? source = null)
         {
             if (!bypassChecks)
                 throwIfLeased();
@@ -94,15 +90,15 @@ public virtual T Value
                 // if the leased bindable decides to disable exclusive access (by setting Disabled = false) then anything will be able to write to Value.
 
                 if (Disabled)
-                    throw new InvalidOperationException($"Can not set value to \"{value.ToString()}\" as bindable is disabled.");
+                    throw new InvalidOperationException($"Can not set value to \"{value}\" as bindable is disabled.");
 
                 if (EqualityComparer<T>.Default.Equals(this.value, value)) return;
 
                 SetValue(this.value, value);
             }
         }
 
-        internal void SetValue(T previousValue, T value, bool bypassChecks = false, Bindable<T> source = null)
+        internal void SetValue(T previousValue, T value, bool bypassChecks = false, Bindable<T>? source = null)
         {
             this.value = value;
             TriggerValueChange(previousValue, source ?? this, true, bypassChecks);
@@ -120,21 +116,21 @@ public virtual T Default
                 // if the leased bindable decides to disable exclusive access (by setting Disabled = false) then anything will be able to write to Default.
 
                 if (Disabled)
-                    throw new InvalidOperationException($"Can not set default value to \"{value.ToString()}\" as bindable is disabled.");
+                    throw new InvalidOperationException($"Can not set default value to \"{value}\" as bindable is disabled.");
 
                 if (EqualityComparer<T>.Default.Equals(defaultValue, value)) return;
 
                 SetDefaultValue(defaultValue, value);
             }
         }
 
-        internal void SetDefaultValue(T previousValue, T value, bool bypassChecks = false, Bindable<T> source = null)
+        internal void SetDefaultValue(T previousValue, T value, bool bypassChecks = false, Bindable<T>? source = null)
         {
             defaultValue = value;
             TriggerDefaultChange(previousValue, source ?? this, true, bypassChecks);
         }
 
-        private WeakReference<Bindable<T>> weakReferenceInstance;
+        private WeakReference<Bindable<T>>? weakReferenceInstance;
 
         private WeakReference<Bindable<T>> weakReference => weakReferenceInstance ??= new WeakReference<Bindable<T>>(this);
 
@@ -143,20 +139,22 @@ internal void SetDefaultValue(T previousValue, T value, bool bypassChecks = fals
         /// </summary>
         [UsedImplicitly]
         private Bindable()
-            : this(default)
+            : this(default!)
         {
         }
 
         /// <summary>
         /// Creates a new bindable instance initialised with a default value.
         /// </summary>
         /// <param name="defaultValue">The initial and default value for this bindable.</param>
-        public Bindable(T defaultValue = default)
+        public Bindable(T defaultValue = default!)
         {
-            value = Default = defaultValue;
+            // TODO: add a custom analyser warning about no default value provided for non-nullable T
+            // remember to also check for derived class constructors
+            value = this.defaultValue = defaultValue;
         }
 
-        protected LockedWeakList<Bindable<T>> Bindings { get; private set; }
+        protected LockedWeakList<Bindable<T>>? Bindings { get; private set; }
 
         void IBindable.BindTo(IBindable them)
         {
@@ -249,7 +247,7 @@ private void addWeakReference(WeakReference<Bindable<T>> weakReference)
         /// </summary>
         /// <param name="input">The input which is to be parsed.</param>
         /// <param name="provider">An object that provides culture-specific formatting information about <paramref name="input"/>.</param>
-        public virtual void Parse(object input, IFormatProvider provider)
+        public virtual void Parse(object? input, IFormatProvider provider)
         {
             switch (input)
             {
@@ -263,7 +261,7 @@ public virtual void Parse(object input, IFormatProvider provider)
                     // Nullable value types and reference types (annotated or not) are allowed to be initialised with `null`.
                     if (typeof(T).IsNullable() || typeof(T).IsClass)
                     {
-                        Value = default;
+                        Value = default!;
                         break;
                     }
 
@@ -283,7 +281,7 @@ public virtual void Parse(object input, IFormatProvider provider)
                         // Nullable value types and reference types are initialised to `null` on empty strings.
                         if (typeof(T).IsNullable() || typeof(T).IsClass)
                         {
-                            Value = default;
+                            Value = default!;
                             break;
                         }
 
@@ -417,11 +415,11 @@ public virtual void UnbindFrom(IUnbindable them)
             tThem.removeWeakReference(weakReference);
         }
 
-        public string Description { get; set; }
+        public string Description { get; set; } = string.Empty;
 
         public sealed override string ToString() => ToString(null, CultureInfo.CurrentCulture);
 
-        public virtual string ToString(string format, IFormatProvider formatProvider) => string.Format(formatProvider, $"{{0:{format}}}", Value);
+        public virtual string ToString(string? format, IFormatProvider? formatProvider) => string.Format(formatProvider, $"{{0:{format}}}", Value);
 
         /// <summary>
         /// Create an unbound clone of this bindable.
@@ -454,11 +452,14 @@ void ISerializableBindable.SerializeTo(JsonWriter writer, JsonSerializer seriali
 
         void ISerializableBindable.DeserializeFrom(JsonReader reader, JsonSerializer serializer)
         {
-            Value = serializer.Deserialize<T>(reader);
+            // Deserialize returns null for json literal "null".
+            // The nullability of type parameter T is unavailable here, so we can't do any validation.
+            Value = serializer.Deserialize<T>(reader).AsNonNull();
         }
 
-        private LeasedBindable<T> leasedBindable;
+        private LeasedBindable<T>? leasedBindable;
 
+        [MemberNotNullWhen(true, nameof(leasedBindable))]
         private bool isLeased => leasedBindable != null;
 
         /// <summary>

osu.Framework/Bindables/BindableDictionary.cs

@@ -417,7 +417,7 @@ private void unbind(BindableDictionary<TKey, TValue> binding)
 
         #region IHasDescription
 
-        public string? Description { get; set; }
+        public string Description { get; set; } = string.Empty;
 
         #endregion IHasDescription
 

osu.Framework/Bindables/BindableList.cs

@@ -1,17 +1,15 @@
 // Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Globalization;
 using System.Linq;
-using JetBrains.Annotations;
 using osu.Framework.Caching;
 using osu.Framework.Extensions.TypeExtensions;
+using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Lists;
 
 namespace osu.Framework.Bindables
@@ -21,27 +19,26 @@ public class BindableList<T> : IBindableList<T>, IBindable, IParseable, IList<T>
         /// <summary>
         /// An event which is raised when this <see cref="BindableList{T}"/> changes.
         /// </summary>
-        public event NotifyCollectionChangedEventHandler CollectionChanged;
+        public event NotifyCollectionChangedEventHandler? CollectionChanged;
 
         /// <summary>
         /// An event which is raised when <see cref="Disabled"/>'s state has changed (or manually via <see cref="triggerDisabledChange(bool)"/>).
         /// </summary>
-        [CanBeNull]
-        public event Action<bool> DisabledChanged;
+        public event Action<bool>? DisabledChanged;
 
         private readonly List<T> collection = new List<T>();
 
         private readonly Cached<WeakReference<BindableList<T>>> weakReferenceCache = new Cached<WeakReference<BindableList<T>>>();
 
         private WeakReference<BindableList<T>> weakReference => weakReferenceCache.IsValid ? weakReferenceCache.Value : weakReferenceCache.Value = new WeakReference<BindableList<T>>(this);
 
-        private LockedWeakList<BindableList<T>> bindings;
+        private LockedWeakList<BindableList<T>>? bindings;
 
         /// <summary>
         /// Creates a new <see cref="BindableList{T}"/>, optionally adding the items of the given collection.
         /// </summary>
         /// <param name="items">The items that are going to be contained in the newly created <see cref="BindableList{T}"/>.</param>
-        public BindableList(IEnumerable<T> items = null)
+        public BindableList(IEnumerable<T>? items = null)
         {
             if (items != null)
                 collection.AddRange(items);
@@ -388,25 +385,25 @@ public void CopyTo(Array array, int index)
 
         #region IList
 
-        object IList.this[int index]
+        object? IList.this[int index]
         {
             get => this[index];
-            set => this[index] = (T)value;
+            set => this[index] = (T)value.AsNonNull();
         }
 
-        int IList.Add(object value)
+        int IList.Add(object? value)
         {
-            Add((T)value);
+            Add((T)value.AsNonNull());
             return Count - 1;
         }
 
-        bool IList.Contains(object value) => Contains((T)value);
+        bool IList.Contains(object? value) => Contains((T)value.AsNonNull());
 
-        int IList.IndexOf(object value) => IndexOf((T)value);
+        int IList.IndexOf(object? value) => IndexOf((T)value.AsNonNull());
 
-        void IList.Insert(int index, object value) => Insert(index, (T)value);
+        void IList.Insert(int index, object? value) => Insert(index, (T)value.AsNonNull());
 
-        void IList.Remove(object value) => Remove((T)value);
+        void IList.Remove(object? value) => Remove((T)value.AsNonNull());
 
         bool IList.IsFixedSize => false;
 
@@ -421,7 +418,7 @@ int IList.Add(object value)
         /// <param name="input">The input which is to be parsed.</param>
         /// <param name="provider">Not valid for <see cref="BindableList{T}"/>.</param>
         /// <exception cref="InvalidOperationException">Thrown if this <see cref="BindableList{T}"/> is <see cref="Disabled"/>.</exception>
-        public void Parse(object input, IFormatProvider provider)
+        public void Parse(object? input, IFormatProvider provider)
         {
             ensureMutationAllowed();
 
@@ -530,7 +527,7 @@ public virtual void UnbindFrom(IUnbindable them)
 
         #region IHasDescription
 
-        public string Description { get; set; }
+        public string Description { get; set; } = string.Empty;
 
         #endregion IHasDescription
 
@@ -690,6 +687,6 @@ private void ensureMutationAllowed()
 
         public bool IsDefault => Count == 0;
 
-        string IFormattable.ToString(string format, IFormatProvider formatProvider) => ((FormattableString)$"{GetType().ReadableName()}({nameof(Count)}={Count})").ToString(formatProvider);
+        string IFormattable.ToString(string? format, IFormatProvider? formatProvider) => ((FormattableString)$"{GetType().ReadableName()}({nameof(Count)}={Count})").ToString(formatProvider);
     }
 }

osu.Framework/Bindables/BindableNumber.cs

@@ -1,20 +1,16 @@
 // Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-#nullable disable
-
 using System;
 using System.Numerics;
-using JetBrains.Annotations;
 using osu.Framework.Utils;
 
 namespace osu.Framework.Bindables
 {
     public class BindableNumber<T> : RangeConstrainedBindable<T>, IBindableNumber<T>
         where T : struct, INumber<T>, IMinMaxValue<T>
     {
-        [CanBeNull]
-        public event Action<T> PrecisionChanged;
+        public event Action<T>? PrecisionChanged;
 
         public BindableNumber(T defaultValue = default)
             : base(defaultValue)
@@ -114,7 +110,7 @@ public override void TriggerChange()
             TriggerPrecisionChange(this, false);
         }
 
-        protected void TriggerPrecisionChange(BindableNumber<T> source = null, bool propagateToBindings = true)
+        protected void TriggerPrecisionChange(BindableNumber<T>? source = null, bool propagateToBindings = true)
         {
             // check a bound bindable hasn't changed the value again (it will fire its own event)
             T beforePropagation = precision;