rewrite.cs

namespace rewrite_code
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (var filePath in File.ReadAllLines(@"p:\temp\files.txt"))
            {
                if (filePath.Contains(@"artifacts\obj"))
                {
                    continue;
                }

                if (filePath.Contains(@"Generated.cs") || 
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\Program.cs" ||
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\ResultSetTracking\SymbolHoldingResultSetTracker.cs"  ||
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\Graph\LsifProject.cs" ||
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\Graph\Item.cs" ||
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\Graph\Moniker.cs" ||
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\Generator.cs" ||
                    filePath == @"P:\roslyn3\src\Features\Lsif\Generator\Graph\Id.cs" ||
                    filePath == @"P:\roslyn3\src\Tools\Source\CompilerGeneratorTools\Source\IOperationGenerator\IOperationClassWriter.cs" || 
                    filePath == @"P:\roslyn3\src\Tools\Source\CompilerGeneratorTools\Source\IOperationGenerator\Model.cs" ||
                    filePath == @"P:\roslyn3\src\Tools\ExternalAccess\Razor\RazorDocumentServiceProviderWrapper.cs" ||
                    filePath == @"P:\roslyn3\src\Tools\ExternalAccess\Razor\IRazorDocumentPropertiesService.cs" ||
                    filePath == @"P:\roslyn3\src\Tools\ExternalAccess\Razor\RazorRemoteHostClient.cs" )
                {
                    continue;
                }

                if (!File.Exists(filePath))
                {
                    Console.WriteLine($"Missing {filePath}");
                    continue;
                }

                using var reader = new StreamReader(filePath, detectEncodingFromByteOrderMarks: true);

                var foundNullable = false;
                var lines = new List<string>();
                var isLastLineBlank = false;
                while (reader.ReadLine() is string line)
                {
                    if (line.StartsWith("#nullable enable"))
                    {
                        foundNullable = true;

                        if (reader.ReadLine() is string nextLine)
                        {
                            // Avoid double blank line after rewrite
                            if (!isLastLineBlank || !string.IsNullOrWhiteSpace(nextLine))
                            {
                                lines.Add(nextLine);
                            }
                        }
                        break;
                    }

                    lines.Add(line);
                    if (line.StartsWith("namespace"))
                    {
                        break;
                    }

                    isLastLineBlank = string.IsNullOrWhiteSpace(line);
                }

                while (reader.ReadLine() is string line)
                {
                    lines.Add(line);
                }

                reader.Close();

                using var writer = new StreamWriter(filePath, append:false, reader.CurrentEncoding);

                var handledNullable = false;

                foreach (var line in lines)
                {
                    if (!handledNullable && !line.StartsWith("//"))
                    {
                        if (!foundNullable)
                        {
                            writer.WriteLine("#nullable disable");
                        }
                        handledNullable = true;
                    }

                    if (line.StartsWith("#nullable restore"))
                    {
                        writer.WriteLine("#nullable disable");
                    }
                    else
                    {
                        writer.WriteLine(line);
                    }
                }
            }    
        }
    }
}