ObservableCollectionChanged shouldn't increment -1 indices for adds #89
Description
The R3 extension method ObserveChanged converts NotifyCollectionChangedEventArgs where IsSingleItem = false into multiple CollectionChangedEvent notifications. There is a consistency issue when the source collection isn't indexed (eg ObservableHashSet):
var collection = new ObservableHashSet<int>();
collection.AddRange(items: [1, 2, 3]);This AddRange operation creates the following notifications:
{
"Action": "Add",
"NewItem": 1,
"OldItem": 0,
"NewStartingIndex": -1,
"OldStartingIndex": -1,
"SortOperation": {
"Index": 0,
"Count": 0,
"Comparer": null,
"IsReverse": false,
"IsClear": true,
"IsSort": false
}
},
{
"Action": "Add",
"NewItem": 2,
"OldItem": 0,
"NewStartingIndex": 0,
"OldStartingIndex": -1,
"SortOperation": {
"Index": 0,
"Count": 0,
"Comparer": null,
"IsReverse": false,
"IsClear": true,
"IsSort": false
}
},
{
"Action": "Add",
"NewItem": 3,
"OldItem": 0,
"NewStartingIndex": 1,
"OldStartingIndex": -1,
"SortOperation": {
"Index": 0,
"Count": 0,
"Comparer": null,
"IsReverse": false,
"IsClear": true,
"IsSort": false
}
},Note that NewStartingIndex gets incremented from -1 to 0 to 1. This is because of this snippet of code:
I believe that NewStartingIndex should be -1 for all three notifications.