Get Roslyn SyntaxToken from Visual Studio Text Selection (caret position)

Question

I am attempting to bridge between the VSSDK and Roslyn SDK in a Visual Studio extension package and have been having a hard time with this. The ActivePoint.AbsoluteCharOffset given from Visual Studio does not match the element I get from Roslyn when using FindToken(offset). I'm fairly sure this has to do with how each side counts EOL characters based on my current working hack but I'm not 100% that my hack is going to hold up in the long run.

My hack is this line: charOffset += point.Line;

I add the number of lines onto the char offset, this seems to work so I'm guessing I am adding in all the line break characters that are being ignored by activepoint counting.

Helpers

private VisualStudioWorkspace workspace = null;
public RoslynUtilities(VisualStudioWorkspace workspace)
{
    this.workspace = workspace;
}
public Solution Solution { get { return workspace.CurrentSolution; } }
public Document GetDocumentFromPath(string fullPath)
{
    foreach (Project proj in this.Solution.Projects)
    {               
        foreach (Document doc in proj.Documents)
        {
            if (doc.FilePath == fullPath)
                return doc;                   
        }
    }
    return null;
}
public SyntaxTree GetSyntaxTreeFromDocumentPath(string fullPath)
{
    Document doc = GetDocumentFromPath(fullPath);
    if (doc != null)
        return doc.GetSyntaxTreeAsync().Result;
    else
        return null;
}
public SyntaxNode GetNodeByFilePosition(string fullPath, int absoluteChar)
{
    SyntaxTree tree = GetSyntaxTreeFromDocumentPath(fullPath);
    if(tree != null)
    {
        var compUnit = tree.GetCompilationUnitRoot();
        if(compUnit != null)
        {
            return compUnit.FindToken(absoluteChar, true).Parent;
        }
    }
    return null;                        
}
private VisualStudioWorkspace GetRoslynWorkspace()
    {
        var componentModel = (IComponentModel)GetGlobalService(typeof(SComponentModel));
        return componentModel.GetService<VisualStudioWorkspace>();
    }

Main Part

EnvDTE80.DTE2 applicationObject = (EnvDTE80.DTE2)GetService(typeof(SDTE));
EnvDTE.TextSelection ts = applicationObject.ActiveWindow.Selection as EnvDTE.TextSelection;
if (ts == null)
    return;

EnvDTE.VirtualPoint point = ts.ActivePoint;
int charOffset = point.AbsoluteCharOffset;
charOffset += point.Line;//HACK ALERT

Parse.Roslyn.RoslynUtilities roslyn = new Parse.Roslyn.RoslynUtilities(GetRoslynWorkspace());
SyntaxNode node = roslyn.GetNodeByFilePosition(applicationObject.ActiveDocument.FullName, charOffset);

Answer 1

I'd highly recommend using Microsoft.VisualStudio.Text.SnapshotPoint from a Microsoft.VisualStudio.Text.Editor.IWpfTextView buffer instead of EnvDTE interfaces to interact with Roslyn.

Main code may look like this:

Microsoft.VisualStudio.Text.Editor.IWpfTextView textView =
    GetTextView();

Microsoft.VisualStudio.Text.SnapshotPoint caretPosition =
    textView.Caret.Position.BufferPosition;

Microsoft.CodeAnalysis.Document document =
    caretPosition.Snapshot.GetOpenDocumentInCurrentContextWithChanges();

Microsoft.CodeAnalysis.CSharp.Syntax.InvocationExpressionSyntax invocationExpressionNode = 
    document.GetSyntaxRootAsync().Result.
        FindToken(caretPosition).Parent.AncestorsAndSelf().
        OfType<Microsoft.CodeAnalysis.CSharp.Syntax.InvocationExpressionSyntax>().
        FirstOrDefault();

See Create a typed variable from the current method invocation for a complete example.