Feat: Add support for empty state in debouncers

Author: AnnaSasDev

src/CodeOfChaos.Extensions.AspNetCore.Components/EventCallbacks/EventCallbackDebouncer.cs

@@ -8,10 +8,18 @@ namespace CodeOfChaos.Extensions.Debouncers;
 // ---------------------------------------------------------------------------------------------------------------------
 // Code
 // ---------------------------------------------------------------------------------------------------------------------
+// ReSharper disable once ConvertToAutoPropertyWithPrivateSetter
 public sealed class EventCallbackDebouncer : DebouncerBase<EventCallbackDebouncer.EmptyUnit> {
     public readonly struct EmptyUnit;
     private EventCallback Callback { get; init; }
-
+    
+    private bool _isEmpty;
+    protected override bool IsEmpty => _isEmpty;
+    public static EventCallbackDebouncer Empty => new() {
+        Callback = default,
+        _isEmpty = true
+    };
+    
     // -----------------------------------------------------------------------------------------------------------------
     // Constructors
     // -----------------------------------------------------------------------------------------------------------------
@@ -26,16 +34,24 @@ public static EventCallbackDebouncer FromEventCallback(EventCallback callback, i
     // -----------------------------------------------------------------------------------------------------------------
     public Task InvokeDebouncedAsync(CancellationToken ct = default) 
         => DebouncerLogicAsync(default, ct);
-    
+
     protected async override ValueTask InvokeCallbackAsync(EmptyUnit item, CancellationToken ct = default) {
         if (ct.IsCancellationRequested) return;
         await Callback.InvokeAsync();
     }
 }
 
+// ReSharper disable once ConvertToAutoPropertyWithPrivateSetter
 public sealed class EventCallbackDebouncer<T> : DebouncerBase<T> {
     private EventCallback<T> Callback { get; init; }
 
+    private bool _isEmpty;
+    protected override bool IsEmpty => _isEmpty;
+    public static EventCallbackDebouncer<T> Empty => new() {
+        Callback = default,
+        _isEmpty = true
+    };
+    
     // -----------------------------------------------------------------------------------------------------------------
     // Constructors
     // -----------------------------------------------------------------------------------------------------------------

src/CodeOfChaos.Extensions/Debouncers/Regular/Debouncer.cs

@@ -8,7 +8,12 @@ namespace CodeOfChaos.Extensions.Debouncers;
 // ---------------------------------------------------------------------------------------------------------------------
 public sealed class Debouncer: DebouncerBase<Debouncer.EmptyUnit> {
     public readonly struct EmptyUnit; // Workaround for reusing DebouncerBase<T> instead of creating a fully new DebouncerBase without generics
-    private object Callback { get; init; } = null!;
+    private object? Callback { get; init; }
+    protected override bool IsEmpty => Callback is null;
+
+    public static Debouncer Empty => new() {
+        Callback = null
+    };
 
     // -----------------------------------------------------------------------------------------------------------------
     // Constructors
@@ -64,7 +69,12 @@ protected async override ValueTask InvokeCallbackAsync(EmptyUnit item, Cancellat
 }
 
 public sealed class Debouncer<T> : DebouncerBase<T> {
-    private object Callback { get; init; } = null!;
+    private object? Callback { get; init; }
+    protected override bool IsEmpty => Callback is null;
+
+    public static Debouncer<T> Empty => new() {
+        Callback = null
+    };
 
     // -----------------------------------------------------------------------------------------------------------------
     // Constructors

src/CodeOfChaos.Extensions/Debouncers/Regular/DebouncerBase.cs

@@ -16,6 +16,8 @@ public abstract class DebouncerBase<T> : IAsyncDisposable {
     private bool _isDisposed;
     private T? _latestValue;
 
+    protected abstract bool IsEmpty { get; }
+
     // -----------------------------------------------------------------------------------------------------------------
     // Methods
     // -----------------------------------------------------------------------------------------------------------------
@@ -24,6 +26,7 @@ public abstract class DebouncerBase<T> : IAsyncDisposable {
     // ReSharper disable once PossiblyMistakenUseOfCancellationToken
     protected async Task DebouncerLogicAsync(T? value = default, CancellationToken ct = default) {
         ObjectDisposedException.ThrowIf(_isDisposed, this);
+        if (IsEmpty) return;
 
         await _semaphore.WaitAsync(ct);
         try {

src/CodeOfChaos.Extensions/Debouncers/Throttled/ThrottledDebouncer.cs

@@ -8,7 +8,12 @@ namespace CodeOfChaos.Extensions.Debouncers;
 // ---------------------------------------------------------------------------------------------------------------------
 public sealed class ThrottledDebouncer: ThrottledDebouncerBase<ThrottledDebouncer.EmptyUnit> {
     public readonly struct EmptyUnit; // Workaround for reusing ThrottledDebouncerBase<T> instead of creating a fully new DebouncerBase without generics
-    private object Callback { get; init; } = null!;
+    private object? Callback { get; init; }
+
+    protected override bool IsEmpty => Callback is null;
+    public static ThrottledDebouncer Empty => new() {
+        Callback = null
+    };
 
     // -----------------------------------------------------------------------------------------------------------------
     // Constructors
@@ -40,7 +45,7 @@ public static ThrottledDebouncer FromDelegate(Func<Task> func, int debounceMs =
     // -----------------------------------------------------------------------------------------------------------------
     public Task InvokeDebouncedAsync(CancellationToken ct = default) 
         => DebouncerLogicAsync(default, ct);
-    
+
     protected async override ValueTask InvokeCallbackAsync(EmptyUnit item, CancellationToken ct = default) {
         if (ct.IsCancellationRequested) return;
 
@@ -67,7 +72,11 @@ protected async override ValueTask InvokeCallbackAsync(EmptyUnit item, Cancellat
 }
 
 public sealed class ThrottledDebouncer<T> : ThrottledDebouncerBase<T> {
-    private object Callback { get; init; } = null!;
+    private object? Callback { get; init; }
+    protected override bool IsEmpty => Callback is null;
+    public static ThrottledDebouncer<T> Empty => new() {
+        Callback = null
+    };
 
     // -----------------------------------------------------------------------------------------------------------------
     // Constructors

src/CodeOfChaos.Extensions/Debouncers/Throttled/ThrottledDebouncerBase.cs

@@ -19,8 +19,9 @@ public abstract class ThrottledDebouncerBase<T> : IAsyncDisposable {
     private bool _isDisposed;
     private T? _latestValue;
     private DateTime _lastExecuteTime = DateTime.MinValue;
-    private DateTime _firstCallTime = DateTime.MinValue; 
+    private DateTime _firstCallTime = DateTime.MinValue;
 
+    protected abstract bool IsEmpty { get; }
 
     // -----------------------------------------------------------------------------------------------------------------
     // Methods
@@ -30,6 +31,7 @@ public abstract class ThrottledDebouncerBase<T> : IAsyncDisposable {
     // ReSharper disable twice PossiblyMistakenUseOfCancellationToken
     protected async Task DebouncerLogicAsync(T? value = default, CancellationToken ct = default) {
         ObjectDisposedException.ThrowIf(_isDisposed, this);
+        if (IsEmpty) return;
 
         await _semaphore.WaitAsync(ct);
         try {