Bugfix/forbid null items

src/DynamicData.Tests/Cache/AutoRefreshFixture.cs

@@ -89,13 +89,13 @@ public void AutoRefreshFromObservable()
     [Fact]
     public void MakeSelectMagicWorkWithObservable()
     {
-        var initialItem = new IntHolder { Value = 1, Description = "Initial Description" };
+        var initialItem = new IntHolder(1, "Initial Description");
 
         var sourceList = new SourceList<IntHolder>();
         sourceList.Add(initialItem);
 
         var descriptionStream = sourceList.Connect().AutoRefresh(intHolder => intHolder!.Description).Transform(intHolder => intHolder!.Description, true).Do(x => { }) // <--- Add break point here to check the overload fixes it
-            .Bind(out ReadOnlyObservableCollection<string?> resultCollection);
+            .Bind(out ReadOnlyObservableCollection<string> resultCollection);
 
         using (descriptionStream.Subscribe())
         {
@@ -109,11 +109,17 @@ public void MakeSelectMagicWorkWithObservable()
 
     public class IntHolder : AbstractNotifyPropertyChanged
     {
-        public string? _description_;
+        public string _description_;
 
         public int _value;
 
-        public string? Description
+        public IntHolder(int value, string description)
+        {
+            _value = value;
+            _description_ = description;
+        }
+
+        public string Description
         {
             get => _description_;
             set => SetAndRaise(ref _description_, value);

src/DynamicData.Tests/Cache/ObservableChangeSetFixture.cs

@@ -217,6 +217,7 @@ public void LoadsAndDisposeUsingDisposableAsync()
 
     private void SubscribeAndAssert<TObject, TKey>(IObservable<IChangeSet<TObject, TKey>> observableChangeset, bool expectsError = false, Action<IObservableCache<TObject, TKey>>? checkContentAction = null)
         where TKey : notnull
+        where TObject : notnull
     {
         Exception? error = null;
         bool complete = false;

src/DynamicData.Tests/Cache/TransformFixture.cs

@@ -135,18 +135,6 @@ public void SameKeyChanges()
         onlyItemInCache.Should().Be(lastTransformed, "Incorrect transform result");
     }
 
-    [Fact]
-    public void TransformToNull()
-    {
-        using var source = new SourceCache<Person, string>(p => p.Name);
-        using var results = new ChangeSetAggregator<PersonWithGender?, string>(source.Connect().Transform((Func<Person, PersonWithGender?>)(p => null)));
-        source.AddOrUpdate(new Person("Adult1", 50));
-
-        results.Messages.Count.Should().Be(1, "Should be 1 updates");
-        results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        results.Data.Items.First().Should().Be(null, "Should be same person");
-    }
-
     [Fact]
     public void Update()
     {

src/DynamicData.Tests/Cache/TransformFixtureParallel.cs

@@ -109,19 +109,6 @@ public void SameKeyChanges()
         onlyItemInCache.Should().Be(lastTransformed, "Incorrect transform result");
     }
 
-    [Fact]
-    public void TransformToNull()
-    {
-        using var source = new SourceCache<Person, string>(p => p.Name);
-        using var results = new ChangeSetAggregator<PersonWithGender?, string>(source.Connect()
-            .Transform((Func<Person, PersonWithGender?>)(p => null), new ParallelisationOptions(ParallelType.Parallelise)));
-        source.AddOrUpdate(new Person("Adult1", 50));
-
-        results.Messages.Count.Should().Be(1, "Should be 1 updates");
-        results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        results.Data.Items.First().Should().Be(null, "Should be same person");
-    }
-
     [Fact]
     public void Update()
     {

src/DynamicData.Tests/List/CreationFixtures.cs

@@ -26,6 +26,7 @@ public void Create()
     }
 
     private void SubscribeAndAssert<T>(IObservable<IChangeSet<T>> observableChangeset, bool expectsError = false)
+        where T : notnull
     {
         Exception? error = null;
         bool complete = false;

src/DynamicData.Tests/List/SortFixture.cs

@@ -51,7 +51,7 @@ public ListItem(int number)
             Number = number;
         }
 
-        public int CompareTo([AllowNull] ListItem other) => DefaultComparer.Compare(this, other);
+        public int CompareTo(ListItem? other) => DefaultComparer.Compare(this, other);
 
     }
 }

src/DynamicData.Tests/List/TransformFixture.cs

@@ -117,19 +117,6 @@ public void SameKeyChanges()
         _results.Data.Count.Should().Be(10, "Should result in 10 records");
     }
 
-    [Fact]
-    public void TransformToNull()
-    {
-        using var source = new SourceList<Person>();
-        using var results = new ChangeSetAggregator<PersonWithGender?>(source.Connect()
-            .Transform((Func<Person, PersonWithGender?>)(p => null)));
-        source.Add(new Person("Adult1", 50));
-
-        results.Messages.Count.Should().Be(1, "Should be 1 updates");
-        results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        results.Data.Items.First().Should().Be(null, "Should be same person");
-    }
-
     [Fact]
     public void Update()
     {

src/DynamicData/Aggregation/AggregateEnumerator.cs

@@ -9,6 +9,7 @@
 namespace DynamicData.Aggregation;
 
 internal class AggregateEnumerator<T> : IAggregateChangeSet<T>
+    where T : notnull
 {
     private readonly IChangeSet<T> _source;
 
@@ -64,6 +65,7 @@ IEnumerator IEnumerable.GetEnumerator()
 
 [SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1402:File may only contain a single type", Justification = "Same name, different generics.")]
 internal class AggregateEnumerator<TObject, TKey> : IAggregateChangeSet<TObject>
+    where TObject : notnull
     where TKey : notnull
 {
     private readonly IChangeSet<TObject, TKey> _source;

src/DynamicData/Aggregation/AggregationEx.cs

@@ -22,6 +22,7 @@ public static class AggregationEx
     /// <param name="source">The source.</param>
     /// <returns>The aggregated change set.</returns>
     public static IObservable<IAggregateChangeSet<TObject>> ForAggregation<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source)
+        where TObject : notnull
         where TKey : notnull
     {
         if (source is null)
@@ -39,6 +40,7 @@ public static class AggregationEx
     /// <param name="source">The source.</param>
     /// <returns>The aggregated change set.</returns>
     public static IObservable<IAggregateChangeSet<TObject>> ForAggregation<TObject>(this IObservable<IChangeSet<TObject>> source)
+        where TObject : notnull
     {
         if (source is null)
         {
@@ -87,6 +89,7 @@ public static IObservable<T> InvalidateWhen<T>(this IObservable<T> source, IObse
     /// <param name="removeAction">The remove action.</param>
     /// <returns>An observable with the accumulated value.</returns>
     internal static IObservable<TResult> Accumulate<TObject, TResult>(this IObservable<IChangeSet<TObject>> source, TResult seed, Func<TObject, TResult> accessor, Func<TResult, TResult, TResult> addAction, Func<TResult, TResult, TResult> removeAction)
+        where TObject : notnull
     {
         return source.ForAggregation().Accumulate(seed, accessor, addAction, removeAction);
     }
@@ -105,6 +108,7 @@ public static IObservable<T> InvalidateWhen<T>(this IObservable<T> source, IObse
     /// <param name="removeAction">The remove action.</param>
     /// <returns>An observable with the accumulated value.</returns>
     internal static IObservable<TResult> Accumulate<TObject, TKey, TResult>(this IObservable<IChangeSet<TObject, TKey>> source, TResult seed, Func<TObject, TResult> accessor, Func<TResult, TResult, TResult> addAction, Func<TResult, TResult, TResult> removeAction)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Accumulate(seed, accessor, addAction, removeAction);

src/DynamicData/Aggregation/AvgEx.cs

@@ -25,6 +25,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, int> valueSelector, int emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -42,6 +43,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, int?> valueSelector, int emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -59,6 +61,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, long> valueSelector, long emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -76,6 +79,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, long?> valueSelector, long emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -93,6 +97,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, double> valueSelector, double emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -110,6 +115,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, double?> valueSelector, double emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -127,6 +133,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<decimal> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, decimal> valueSelector, decimal emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -144,6 +151,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<decimal> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, decimal?> valueSelector, decimal emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -161,6 +169,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<float> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, float> valueSelector, float emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -178,6 +187,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<float> Avg<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source, Func<TObject, float?> valueSelector, float emptyValue = 0)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
@@ -194,6 +204,7 @@ public static class AvgEx
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, int> valueSelector, int emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -209,6 +220,7 @@ public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, int?> valueSelector, int emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -224,6 +236,7 @@ public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, long> valueSelector, long emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -239,6 +252,7 @@ public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, long?> valueSelector, long emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -254,6 +268,7 @@ public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, double> valueSelector, double emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -269,6 +284,7 @@ public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, double?> valueSelector, double emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -284,6 +300,7 @@ public static IObservable<double> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<decimal> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, decimal> valueSelector, decimal emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -299,6 +316,7 @@ public static IObservable<decimal> Avg<T>(this IObservable<IChangeSet<T>> source
     /// An observable of averages.
     /// </returns>
     public static IObservable<decimal> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, decimal?> valueSelector, decimal emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -314,6 +332,7 @@ public static IObservable<decimal> Avg<T>(this IObservable<IChangeSet<T>> source
     /// An observable of averages.
     /// </returns>
     public static IObservable<float> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, float> valueSelector, float emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }
@@ -329,6 +348,7 @@ public static IObservable<float> Avg<T>(this IObservable<IChangeSet<T>> source,
     /// An observable of averages.
     /// </returns>
     public static IObservable<float> Avg<T>(this IObservable<IChangeSet<T>> source, Func<T, float?> valueSelector, float emptyValue = 0)
+        where T : notnull
     {
         return source.ForAggregation().Avg(valueSelector, emptyValue);
     }

src/DynamicData/Aggregation/CountEx.cs

@@ -20,6 +20,7 @@ public static class CountEx
     /// <param name="source">The source.</param>
     /// <returns>An observable which emits the count.</returns>
     public static IObservable<int> Count<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Count();
@@ -32,6 +33,7 @@ public static class CountEx
     /// <param name="source">The source.</param>
     /// <returns>An observable which emits the count.</returns>
     public static IObservable<int> Count<TObject>(this IObservable<IChangeSet<TObject>> source)
+        where TObject : notnull
     {
         return source.ForAggregation().Count();
     }
@@ -68,6 +70,7 @@ public static IObservable<int> Count<TObject>(this IObservable<IDistinctChangeSe
     /// <param name="source">The source.</param>
     /// <returns>An observable which emits the count.</returns>
     public static IObservable<bool> IsEmpty<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Count().StartWith(0).Select(count => count == 0);
@@ -81,6 +84,7 @@ public static IObservable<int> Count<TObject>(this IObservable<IDistinctChangeSe
     /// <param name="source">The source.</param>
     /// <returns>An observable which emits the count.</returns>
     public static IObservable<bool> IsEmpty<TObject>(this IObservable<IChangeSet<TObject>> source)
+        where TObject : notnull
     {
         return source.ForAggregation().Count().StartWith(0).Select(count => count == 0);
     }
@@ -94,6 +98,7 @@ public static IObservable<bool> IsEmpty<TObject>(this IObservable<IChangeSet<TOb
     /// <param name="source">The source.</param>
     /// <returns>An observable which emits the count.</returns>
     public static IObservable<bool> IsNotEmpty<TObject, TKey>(this IObservable<IChangeSet<TObject, TKey>> source)
+        where TObject : notnull
         where TKey : notnull
     {
         return source.ForAggregation().Count().StartWith(0).Select(count => count > 0);
@@ -107,6 +112,7 @@ public static IObservable<bool> IsEmpty<TObject>(this IObservable<IChangeSet<TOb
     /// <param name="source">The source.</param>
     /// <returns>An observable which emits the count.</returns>
     public static IObservable<bool> IsNotEmpty<TObject>(this IObservable<IChangeSet<TObject>> source)
+        where TObject : notnull
     {
         return source.ForAggregation().Count().StartWith(0).Select(count => count > 0);
     }