Hello all - been tinkering on ghcitty (a small Rust wrapper around GHCi)
It should be about ready for sea-trials by others.
Would love your veteran feedback (any commands that feel off when wrapped? … any multiline weirdness?)
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This looks like a cutesy little utility, thanks for sharing! I’m installing it as I type, and will provide feedback in time.
I’ll ask the expected question: Is there a reason (other than familiarity or ecosystem, which is perfectly valid!) that the project is in Rust as opposed to Haskell?
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Hello hello! Thanks for taking a peek 
for why Rust, honestly ease of :
- standing up a v1 (its built on top of nushell’s reedline)
- having a easy to distribute binary
in the background am whittling away on implementing some of the reedline niceties in raw Haskell… but will take some more time
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What problems have you faced with distributing Haskell binaries? I’ve been doing this with my own projects for some time and I’m interested in your experience.
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Hello! Problems is maybe not the word I’d use … but definitely have had to do some incantations with musl GHC, alpine and static-nix
tbf … #1 above / the reedline niceties were definitely the main consideration here for v1)
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My requests:
I’d like support for Option+tab/Command+tab/Ctrl+tab for navigating the command line. As far as I can tell, only normal arrow keys are supported. This is probably one of the only things keeping me from using this fully.
When GHC suggests enabling an extension/flag, having an option to just auto enable it would be cool. e.g.
Proxy :: Proxy [2,3]
GHC will error and suggest enabling DataKinds. It would be nice if I had the option of saying :set -XDataKinds or :seti -XDataKinds.
When there’s only one option for auto-complete, and it’s getting ghost-completed, tab maybe should auto complete. e.g. -XAllowAmb\t should become -XAllowAmbiguousTypes.
It would be nice if λ> fib :: Int would prompt for the definition of fib. I could see a command, :fun or something allowing for this. e.g. λ>:fun fib :: Int, or :sig would just mean prompt for more text, and wait until two newlines were finished. I like this more than :{ }: because it’s two less lines, and also feels more like writing Haskell in a .hs file.
Less opinionated notes/issues:
:! has some problems. Firstly :! ls will try and do syntax highlighting on the files. I’m not sure what to do about that. On one hand, cat X.hs maybe should be highlighted, but :! ls shouldn’t be. A graver issue though is that when I did :! cat app/Main.hs, it just hung. Is :! fully supported for large strings? (:! less app/Main.hs) hung as well.
I think ^C should stop the subprocess first, then ghctty. e.g.
λ> :{
fib 0 = 0
fib 1 = 1
fib n = fib (n-1) + fib (n-2)
:}
fib :: (Eq t1, Num t1, Num t2) => t1 -> t2
λ> fib 1000
^C
Should only end the inner process, not the outer one. Also, if you want to model GHCI , then ^Z should quit ghcitty.
As far as I can tell, when the process ends with ^C currently, history isn’t saved. e.g.
λ> <complex expr>
λ> <hanging expr>
^C
<complex expr> never gets added to history.
:set editor only lasts one session, but I think people usually only use 1 editor. Maybe it should be persistent?
Thank you so much for this tool, it’s really quite amazing and I really appreciate it! Don’t feel pressured by this.
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beauty - tysm for taking a peek! love this auto suggest of missing extension flags and this :fun style syntax for function definition (gonna mull over the latter but chef’s kiss directionally)
Think I got everything captured in the issues (but feel free to add)
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I think you missed the history bug. (It doesn’t save when exited with ^C) Also ^Z maybe should quit to be like GHCI. There’s also auto enabling of GHC flags.
I think you have everything else, but its fine if you don’t implement most of them. If even only #7 and #4 were fixed, I think I’d always use it instead of GHCI. Even without that, I’ll probably still use this a lot.
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Related to navigation there’s also ctrl+backspace/option+delete, for deleting words. If you got full compatibility with GHCI in those, I think ghcitty would be undoubtedly superior.
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Circling back on tab completion behaviour I see 3 options
- Option 1 (disambiguate by candidate count) … 1 candidate accepts … >2 candidates opens menu like today
- Option 2 (split keys) … always opens menu… at end-of-line accepts the ghost
- Option 3 (double tap) accepts ghost… opens menu
Leaning towards and Option 1 + Option 2 hybrid..
- SINGLE cadidate accepts (multiple candidate opens menu)
- accepts ghost as an always available alternative
But lmk what you think
scooped these fixes up in 0.2.0
fresh ghcitty binary is on crates (link)
Tysm for the eagle eye and taking this for a spin!
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@mattlianje How to pass cabal options and stack options, like --allow-newer?
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Added support for this just now w/ 0.3.0 ! ty for all the good catches and suggestions
We can now just do:
ghcitty -- --allow-newer
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