fixes #58 detect non interactive terminals

[marcellourbani]

I'm having second thoughts on this implementation.

• supportsANSI will fail on a dumb terminal, which can still be interactive, although without the bells and whistles
• hIsTerminalDevice from System.IO would be better on non-windows, but will fail on mintty
• isatty from hsshellscript looks Posix only, wonder wether it works in windows

So I plan to check both supportsANSI and hIsTerminalDevice, and only force noninteractive if both fail

PS: should we add an option to force interactivity to support tools like expect?

[chshersh]

@marcellourbani The fixes look great 👍🏻 I believe, the only difficulties left are:

• Proper cross-platform interactivity detection
• Separate handling for stdout and stderr

I'm not an expert on the first one. So I don't have a strong opinion on this. We can go with the simplest reasonable option for now and change later when it's not enough. Nobody pays me to support exotic shells. So if the standard library doesn't have an out-of-the-box cross-platform solution, what can I do 🤷🏻

I agree that the --no-input flag is responsible for multiple use cases:

1. Disabling asking questions.
2. Don't do interactive things like progress bars.

As for the second one, let's check only stdin. I've consulted the CLI guidelines and they recommend checking only stdin:

• https://clig.dev/#interactivity

I believe, I confused --no-input with --no-colour a bit 🥴

So, a simple solution would be to just run hSupportsANSI on stdout and be done with it 👏🏻

[marcellourbani]

@chshersh

Nobody pays me to support exotic shells. So if the standard library doesn't have an out-of-the-box cross-platform solution, what can I do 🤷🏻

What about letting the user override?

data RequestedInteractiveMode
    = RInteractive
    | RNonInteractive
    | RAutoDetect

data InteractiveMode
    = Interactive
    | NonInteractive

handleInteractiveMode :: RequestedInteractiveMode -> IO InteractiveMode

or simply:

handleInteractiveMode :: Maybe RequestedInteractiveMode -> IO InteractiveMode

so by default we autodetect, but users can force either way

[chshersh]

@marcellourbani Overriding interactivity is something I'd like to avoid. We can't output interactive info in a non-interactive terminal so it doesn't make sense. Also, there's no appropriate CLI flag for that and since it's a global default, I'd like to avoid polluting global namespace with non-standard flags.

I'm happy to accept support of exotic shells like minTTY and Cygwin. So, if you want to work on supporting and testing them, feel free to continue working on this issue and taking as much time as you want 🤗

I was mostly implying that the changes might be unreliable without the ability to test this on CI, so the support will be potentially fragile. And if someone wants to contribute the support of these shells and verify that it works for them, I'm happy to accept this change! But I personally don't have the capacity for that. And I wouldn't ask contributors to do such huge work either 🙏🏻

[marcellourbani]

Thank you for the mentoring!