Source generators get the referencing project path - retrieve useful value from IncrementalValueProvider<string>

Question

I am discovering the concept of source generators.

In order to execute some logic with a source generator on some files (image files more precisely) based on the folders structure of the targeted/referencing project, I need to:

• Get the path/Directory of the targeted/referencing project.

First approach

namespace SourceGen
{
    [Generator]
    public class Class1 : IIncrementalGenerator
    {
        public void Initialize(IncrementalGeneratorInitializationContext context)
        {
            var projDirectory = context.AnalyzerConfigOptionsProvider
                           .Select((x, _) => x.GlobalOptions
                           .TryGetValue("build_property.MSBuildProjectDirectory", out var projectDirectory) ? projectDirectory : null);

            File.AppendAllText("\\" + "log.txt", projDirectory );
        }
    }
}

I am logging to a file for debugging purposes (to check the property value I am reading in this case) since I can't find another way to debug this kind of project.

In the log file I get, since IncrementalValueProvider<string>.ToString() returns the type and not whatever value is there:

Microsoft.CodeAnalysis.IncrementalValueProvider`1[System.string].

Second approach

following https://stackoverflow.com/a/66548212 :

var mainSyntaxTree = context.CompilationProvider.Select((x, _) => x.SyntaxTrees.First(x => x.HasCompilationUnitRoot));
var directory = Path.GetDirectoryName(mainSyntaxTree.Select((x, _) => x.FilePath);

The same issue Path.GetDirectoryName() is complaining that the provided parameter is of type IncrementalValueProvider<string> while expecting a string. Not sure how can I get a useful string value (FilePath) out of the type IncrementalValueProvider<string>.

Third approach

This time the log file was not written/created at all:

var provider = context.AnalyzerConfigOptionsProvider.Select((x, _) =>
       {
        x.GlobalOptions.TryGetValue("build_property.MSBuildProjectDirectory", out var projectDirectory);
       File.AppendAllText("\\" + "log.txt", "testing" + projectDirectory);
       return projectDirectory;
       });

Docs: https://github.com/dotnet/roslyn/blob/main/docs/features/incremental-generators.cookbook.md