[IncrementalLoadingCollection] CurrentPageIndex should not increase if LoadDataAsync failed.

[HppZ]

var result = await Source.GetPagedItemsAsync(CurrentPageIndex++, ItemsPerPage, cancellationToken);
I think CurrentPageIndex should not increase if LoadDataAsync failed.

Hello HppZ, thank you for your interest in Windows Community Toolkit!

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[Kyaa-dost]

Thanks, @HppZ for highlighting the issue. I will open this up for discussion with the community and see what they think about this.

[michael-hawker]

@HppZ is there a particular case you're seeing this fail? Or you just meant in general if it's a failed http request or something?

Thinking we should have some tests around these scenario to ensure we don't skip pages either if multiple requests come in at once. The behavior of ISupportIncrementalLoading isn't really well specified in the docs.

This code has been like this for a long time now, so let's move this to 7.1. We should add a suite of Unit Test scenarios to get expected behavior down, and then adjust our code from there to match.