Possible fix for IsNonDirectiveLine

gistfile1.txt

    public interface IDirectiveLineProcessor : ILineProcessor
    {
        bool Matches(string line);
    }
    
    public abstract class DirectiveLineProcessor : ILineProcessor
    {
        ...
        public bool Matches(string line)
        {
            return line.Trim(' ').StartsWith(DirectiveString);
        }
        ...
    }
    
    public class FilePreProcessor : IFilePreProcessor
    {
        ...
        private static bool IsNonDirectiveLine(string line)
        {
            var trimmedLine = line.TrimStart(' ');
            
            return line.Trim() != string.Empty && !_lineProcessors.Where(lp => lp is IDirectiveLineProcessor).Any(lp => lp.Matches(line));
        }
        ...
    }