Stream: beginners

Topic: listing files in a directory

Jakub (Nov 20 2023 at 21:45):

@Brian Carroll thanks a lot for the recommendation. By gluing together few examples I managed to put together something that should give me a list of files, but because I don't really know what I'm doing yet - it fails. I want to figure it out on my own but I'm not really sure where can I find all the error types in the task result section:

app "file-read"
    packages { pf: "https://github.com/roc-lang/basic-cli/releases/download/0.5.0/Cufzl36_SnJ4QbOoEmiJ5dIpUxBvdB3NEySvuH82Wio.tar.br" }
    imports [
        pf.Stdout,
        pf.Task.{ Task },
        pf.Path,
        pf.Env,
        pf.Dir,
    ]
    provides [main] to pf

main =
    task =
        cwd <- Env.cwd |> Task.await

        dirEntries <- Dir.list cwd |> Task.await
        contentsStr = Str.joinWith (List.map dirEntries Path.display) "\n    "
        Stdout.line contentsStr

    Task.attempt task \result ->
        when result is
            Ok {} -> Stdout.line "Success"
            Err err ->
                msg =
                    when err is
                        IOError _ _ -> "Error reading dir"
                        DecodeError -> "Decode Error"
                        _ -> "there was an error!"
                Stdout.line msg

Notification Bot (Nov 20 2023 at 21:51):

A message was moved here from #introductions > introductions by Richard Feldman.

Richard Feldman (Nov 20 2023 at 21:51):

@Jakub welcome! :wave:

Richard Feldman (Nov 20 2023 at 21:51):

would you mind printing out the error you're seeing?

Jakub (Nov 20 2023 at 21:52):

I'm getting there was an error!

Jakub (Nov 20 2023 at 21:55):

Debian GNU/Linux 11 I'm using mcr.microsoft.com/devcontainers/base:bullseye in VSCode DevContainers. BTW I was thinking about creating dev Docker image in case people would like to try out Roc without having to go through the installation process. Would it add any value / help anyone?

Jakub (Nov 20 2023 at 21:58):

and one more thing, the code above is a clumsy copy / paste of: https://raw.githubusercontent.com/roc-lang/roc/main/examples/cli/file.roc - I tried to go backwards to get to the shortest code that could possibly work. Maybe I'm importing a wrong platform...

Luke Boswell (Nov 20 2023 at 22:37):

Yeah so Dir.list on basic cli is currently unimplemented and is returning an error tag rather than crashing or panicking in rust.

Jakub (Nov 20 2023 at 22:43):

fixing this might be beyond my current grasp of internals of Roc but as a genera question, does it make sense to write tests for functions kept in roc/examples/cli/cli-platform/src/lib.rs

Luke Boswell (Nov 20 2023 at 22:45):

I have been talking about https://github.com/roc-lang/basic-cli sorry for any confusion

Anton (Nov 21 2023 at 12:22):

Hi @Jakub,
I'll look into the DIr.list failure, in the meantime you could use the ls command as a workaround.

I was thinking about creating dev Docker image in case people would like to try out Roc without having to go through the installation process.

You can add a Dockerfile to the repo if you are also willing to set up a github workflow to test it, see this script for inspiration.

Anton (Nov 21 2023 at 16:39):

There is now an issue for setting up a docker image #6045

Last updated: Jul 26 2025 at 12:14 UTC