AutoRefresh: Aggregates fail

[SirRufo]

This unit test did not pass, as the Aggregates Sum and Count were not updated although the notification messages were fine.

What am I missing here?

using DynamicData;
using DynamicData.Aggregation;
using DynamicData.Binding;
using DynamicData.Tests;

using ReactiveUI;
using ReactiveUI.Fody.Helpers;

namespace ReactiveBugs;

public class UnitTest1
{
    [Fact]
    public void Test()
    {
        Item[] items = Enumerable.Range(1, 3)
            .Select(id => new Item(id, $"Item {id}") { IsSelected = true, Amount = 1 }).ToArray();
        using SourceCache<Item, int> cache = new(x => x.Id);
        IObservable<IChangeSet<Item, int>> changeset = cache
            .Connect()
            .AutoRefreshOnObservable(p => p.WhenAnyPropertyChanged());
        using ChangeSetAggregator<Item, int> results = changeset.AsAggregator();

        // Count
        int selectionCount = 0;
        using IDisposable selectionCountSubscription =
            changeset.Filter(x => x.IsSelected).Count().Subscribe(x => selectionCount = x);
        // Sum
        int totalAmount = 0;
        using IDisposable totalAmountSubscription = changeset.Sum(x => x.Amount).Subscribe(x => totalAmount = x);

        cache.AddOrUpdate(items);

        Assert.Equal(3, results.Data.Count);
        Assert.Equal(1, results.Messages.Count);
        Assert.Equal(3, selectionCount); // every item is selected
        Assert.Equal(3, totalAmount); // every item has 1 as amount

        items[0].Amount = 2; // 1 -> 2
        Assert.Equal(3, results.Data.Count);
        Assert.Equal(2, results.Messages.Count);

        items[0].IsSelected = false; // true -> false
        Assert.Equal(3, results.Data.Count);
        Assert.Equal(3, results.Messages.Count);

        Assert.Equal(2, selectionCount); // fails
        Assert.Equal(4, totalAmount); // fails
    }

    public class Item(int id, string name) : ReactiveObject
    {
        public int Id { get; } = id;

        [Reactive] public string Name { get; set; } = name;
        [Reactive] public bool IsSelected { get; set; }
        [Reactive] public int Amount { get; set; }
    }
}

[JakenVeina]

You're not missing anything. The DynamicData Aggregation operators do not support refresh changes. Not for any particularly good reason that I'm aware of, mind you.

I will note that the selectionCount test is working perfectly fine, for me, it's just the totalAmount test that's failing. That makes sense, as the .Filter() translates Refresh changes on .IsSelected into Add and Remove changes, which work just fine.

As a workaround, then, you can do this to get the .Sum() working...

using var totalAmountSubscription2 = itemChanges
    .Transform(static item => item.Amount, transformOnRefresh: true)
    .Sum(static amount => amount)