WIP gren run stdin fix

[blaix]

Working on #341

[blaix]

I never see this fire if the program I'm running reads from stdin. For example, this program works fine:

main =
    Node.defineSimpleProgram <| \env ->
        Stream.Log.line env.stdout "Done"
            |> Node.endSimpleProgram

gren run Main will show the Exited log and exit.

But this one will hang after hitting enter and never show the Exited log:

main =
    Node.defineSimpleProgram <| \env ->
        Stream.readBytesAsString env.stdin
            |> Task.onError (\_ -> Task.succeed "")
            |> Node.endSimpleProgram

But if you run the same program directly (node .gren/app) the program does not hang.

[robinheghan]

I think I know what's going on.

                        [ Task.succeed { source = output, target = model.stdout }
                        , Task.succeed { source = model.stdin, target = input }
                        , Task.succeed { source = error, target = model.stderr }
                        ]
                            |> Array.map (Task.attempt RedirectTerminalIO)
                            |> Cmd.batch

RedirectTerminalIO will call Stream.read on model.stdin twice, once for the compiler, then again for the program to run.

The second time Stream.read is called, it will fail with a Locked error (as we're still waiting for the Stream.read to finish from the compilation. The program will never receive a message on its stdin, as the Stream.read has failed.

I think we need to handle stdin specially.

I would create a RedirectStdin message, which begins by calling Stream.read model.stdin. Once/if we get some data from stdin, we can pass that content on to model.stdinRedirectTarget (or something) which is a Maybe Stream.Writable.

[blaix]

Maybe I'm misunderstanding you, but the program does receive stdin. For example:

main =
    Node.defineSimpleProgram <| \env ->
        Stream.readBytesAsString env.stdin
            |> Task.onError (\_ -> Task.succeed "")
            |> Task.andThen (Stream.Log.line env.stdout)
            |> Node.endSimpleProgram

If I enter text it will print, but still hang and never show the Exited log.

Regardless, I still think it's worth trying to handle stdin redirection separately. I'll give it a shot.

[blaix]

I'm wondering if what I want is a connection type for spawn that results in node calling the child process with detached: true and stdio: inherit. That seems to be how you'd get the behavior I want: "spawn this with shared stdio but let the parent program exit" and wouldn't require run to do any stdio redirection.

[blaix]

Hm, actually Integrated seems to be doing what I want. Going to do some more testing and cleanup and get a real PR out ready for review, might take until sometime tomorrow.

[blaix]

Going to open a new PR for a clean review of the fix