private void TrackChangeInSpan(SourceText oldText, TextSpan originalSpan, SourceText newText, out TextSpan changedSpan, out TextSpan changeEncompassingSpan)
{
var affectedRange = newText.GetEncompassingTextChangeRange(oldText);
// The span of text before the edit which is being changed
changeEncompassingSpan = affectedRange.Span;
if (!originalSpan.Contains(changeEncompassingSpan))
{
_logger.LogDebug($"The changed region {changeEncompassingSpan} was not a subset of the span {originalSpan} being tracked. This is unexpected.");
}
// We now know what was the range that changed and the length of that span after the change.
// Let's now compute what the original span looks like after the change.
// We know it still starts from the same location but could have grown or shrunk in length.
// Compute the change in length and then update the original span.
var changeInOriginalSpanLength = affectedRange.NewLength - changeEncompassingSpan.Length;
changedSpan = TextSpan.FromBounds(originalSpan.Start, originalSpan.End + changeInOriginalSpanLength);
}
