private static bool TopLevelChanged(SyntaxTree oldTree, SourceText oldText, SyntaxTree newTree, SourceText newText)
{
// ** currently, it doesn't do any text based quick check. we can add them later if current logic is not performant enough for typing case.
var change = newText.GetEncompassingTextChangeRange(oldText);
if (change == default)
{
// nothing has changed
return(false);
}
// if texts are small enough, just use the equivalent to find out whether there was top level edits
if (oldText.Length < MaxTextChangeRangeLength && newText.Length < MaxTextChangeRangeLength)
{
var topLevel = !newTree.IsEquivalentTo(oldTree, topLevel: true);
return(topLevel);
}
// okay, text is not small and whole text is changed, then we always treat it as top level edit
if (change.NewLength == newText.Length)
{
return(true);
}
// if changes are small enough, we use IsEquivalentTo to find out whether there was a top level edit
if (change.Span.Length < MaxTextChangeRangeLength && change.NewLength < MaxTextChangeRangeLength)
{
var topLevel = !newTree.IsEquivalentTo(oldTree, topLevel: true);
return(topLevel);
}
// otherwise, we always consider top level change
return(true);
}
// Returns the minimal TextSpan that encompasses all the differences between the old and the new text.
protected static void TrackEncompassingChange(SourceText oldText, SourceText newText, out TextSpan spanBeforeChange, out TextSpan spanAfterChange)
{
if (oldText is null)
{
throw new ArgumentNullException(nameof(oldText));
}
if (newText is null)
{
throw new ArgumentNullException(nameof(newText));
}
var affectedRange = newText.GetEncompassingTextChangeRange(oldText);
spanBeforeChange = affectedRange.Span;
spanAfterChange = new TextSpan(spanBeforeChange.Start, affectedRange.NewLength);
}
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);
}