IncrementalGenerator stopped working in VS 17.11

[nvborisenko]

Version Used: Visual Studio 17.11.1

Steps to Reproduce:

1. Create simple incremental generator (it generates source code based on *.txt files as input)

Simple incremental generator (took from docs):

    [Generator]
    public class Generator : IIncrementalGenerator
    {
        public void Initialize(IncrementalGeneratorInitializationContext initContext)
        {
            // define the execution pipeline here via a series of transformations:

            // find all additional files that end with .txt
            IncrementalValuesProvider<AdditionalText> textFiles = initContext.AdditionalTextsProvider.Where(file => file.Path.EndsWith(".txt"));

            // read their contents and save their name
            IncrementalValuesProvider<(string name, string content)> namesAndContents = textFiles.Select((text, cancellationToken) => (name: Path.GetFileNameWithoutExtension(text.Path), content: text.GetText(cancellationToken).ToString()));

            // generate a class that contains their values as const strings
            initContext.RegisterSourceOutput(namesAndContents, (spc, nameAndContent) =>
            {
                File.AppendAllText("E:\\Generator.log", "I am called\n");

                spc.AddSource($"ConstStrings.{nameAndContent.name}", $@"
    public static partial class ConstStrings
    {{
        public const string {nameAndContent.name} = ""{nameAndContent.content}"";
    }}");
            });
        }
    }

Expected Behavior:

Each time when I add or change any *.txt file I should see new file at E:\\Generator.log path.

Actual Behavior:
Incremental generator is invoked only once at build stage. But seems it is not invoked when I add new *.txt file or edit its content.

NOTE:
It worked well in VS 17.10, seems stopped working in 17.11

[CyrusNajmabadi]

This is controlled by:

We also fixed this in 17.12: #74542

Primary issue was that we weren't tracking saves to non-Roslyn files (like your text file). So even saving them wasn't causing generators to rerun.