private static TextChangeRange ExtendToAffectedRange(
CSharp.CSharpSyntaxNode oldTree,
TextChangeRange changeRange
)
{
// we will increase affected range of the change by the number of lookahead tokens
// original code in Blender seem to imply the lookahead at the end of a node is 1 token
// max. TODO: 1 token lookahead seems a bit too optimistic. Increase if needed.
const int maxLookahead = 1;
// check if change is not after the end. TODO: there should be an assert somewhere about
// changes starting at least at the End of old tree
var lastCharIndex = oldTree.FullWidth - 1;
// Move the start of the change range so that it is contained within oldTree.
var start = Math.Max(Math.Min(changeRange.Span.Start, lastCharIndex), 0);
// the first iteration aligns us with the change start. subsequent iteration move us to
// the left by maxLookahead tokens. We only need to do this as long as we're not at the
// start of the tree. Also, the tokens we get back may be zero width. In that case we
// need to keep on looking backward.
for (var i = 0; start > 0 && i <= maxLookahead;)
{
var token = oldTree.FindToken(start, findInsideTrivia: false);
Debug.Assert(
token.Kind() != SyntaxKind.None,
"how could we not get a real token back?"
);
start = Math.Max(0, token.Position - 1);
// Only increment i if we got a non-zero width token. Otherwise, we want to just do
// this again having moved back one space.
if (token.FullWidth > 0)
{
i++;
}
}
if (IsInsideInterpolation(oldTree, start))
{
// If the changed range starts inside an interpolated string, we
// move the start of the change range to the beginning of the line so that any
// interpolated string literal in the changed range will be scanned in its entirety.
var column =
oldTree.SyntaxTree.GetLineSpan(new TextSpan(start, 0)).Span.Start.Character;
start = Math.Max(start - column, 0);
}
var finalSpan = TextSpan.FromBounds(start, changeRange.Span.End);
var finalLength = changeRange.NewLength + (changeRange.Span.Start - start);
return(new TextChangeRange(finalSpan, finalLength));
}
private static bool IsInsideInterpolation(CSharp.CSharpSyntaxNode oldTree, int start)
{
var token = oldTree.FindToken(start, findInsideTrivia: false);
for (var parent = token.Parent; // for each parent
parent != null;
parent = parent.Parent)
{
if (parent.Kind() == SyntaxKind.InterpolatedStringExpression)
{
return(true);
}
}
return(false);
}