Improve wrapper cradle errors

[hasufell]

@jhrcek

wrt #2675 (comment)

[hasufell]

@jhrcek build via:

ghcup compile hls -r https://github.com/hasufell/haskell-language-server.git -g improve-wrapper-error --ghc 8.10.7

[jhrcek]

Thank you @hasufell , you're really fast!

I'm getting this error:

Failed to get project GHC executable path:CradleError {cradleErrorDependencies = [], cradleErrorExitCode = ExitFailure 1, cradleErrorStderr = ["Error when calling stack exec ghc -- -v0 -package-env=- -e putStr =<< System.Environment.getExecutablePath","","\n<interactive>:0:1: error: Variable not in scope: putStr\n\n<interactive>:0:8: error:\n    Variable not in scope:\n      (=<<) :: t0 -> GHC.Types.IO GHC.IO.FilePath -> t\n"]}

[hasufell]

Thank you @hasufell , you're really fast!

I'm getting this error:

Failed to get project GHC executable path:CradleError {cradleErrorDependencies = [], cradleErrorExitCode = ExitFailure 1, cradleErrorStderr = ["Error when calling stack exec ghc -- -v0 -package-env=- -e putStr =<< System.Environment.getExecutablePath","","\n<interactive>:0:1: error: Variable not in scope: putStr\n\n<interactive>:0:8: error:\n    Variable not in scope:\n      (=<<) :: t0 -> GHC.Types.IO GHC.IO.FilePath -> t\n"]}

Uh... can you run

stack exec ghc -- -v0 -package-env=- -e 'putStr =<< System.Environment.getExecutablePath'

inside your project? What if you run it outside of your project? Is NoImplicitPrelude activated?

What are the contents of ~/.stack/global-project/stack.yaml.

[hasufell]

Yeah, pretty sure it's NoImplicitPrelude:

stack exec ghc -- -XNoImplicitPrelude -v0 -package-env=- -e 'putStr =<< System.Environment.getExecutablePath'

<interactive>:0:1: error: Variable not in scope: putStr

<interactive>:0:8: error:
    Variable not in scope:
      (=<<) :: t0 -> GHC.Types.IO GHC.IO.FilePath -> t

[jhrcek]

Outside of any project it works fine

~> stack exec ghc -- -v0 -package-env=- -e "putStr =<< System.Environment.getExecutablePath"
/home/jhrcek/.stack/programs/x86_64-linux/ghc-tinfo6-8.10.7/lib/ghc-8.10.7/bin/ghc

within our work codebase it doesn't:

~/Devel/github.com/Holmusk/PI/backend> stack exec ghc -- -v0 -package-env=- -e "putStr =<< System.Environment.getExecutablePath"

<interactive>:0:1: error: Variable not in scope: putStr

<interactive>:0:8: error:
    Variable not in scope:
      (=<<) :: t0 -> GHC.Types.IO GHC.IO.FilePath -> t

Indeed we are using NoImplicitPrelude 😄

[hasufell]

Ok, I'll push a fix to this PR.

[hasufell]

@jhrcek please try again

[jhrcek]

$ stack exec ghc -- -v0 -package-env=- -e "Prelude.putStr Prelude.=<< System.Environment.getExecutablePath"

<interactive>:0:1: error:
    Not in scope: ‘Prelude.putStr’
    No module named ‘Prelude’ is imported.

<interactive>:0:16: error:
    Not in scope: ‘Prelude.=<<’
    No module named ‘Prelude’ is imported.

I should mention that we're using Relude + base-noprelude, basically setup described here
https://github.com/kowainik/relude#base-noprelude

[jhrcek]

I wonder if it woulndn't be maybe easier to do

$ stack exec ghc -- -v0  -e "System.Environment.getExecutablePath"
"/home/jhrcek/.stack/programs/x86_64-linux/ghc-tinfo6-8.10.7/lib/ghc-8.10.7/bin/ghc"

and then strip the quotes?

Or alternatively use System.IO.putStr to avoid Prelude altogether?

[hasufell]

stack exec ghc -- -XNoImplicitPrelude -v0 -package-env=- -e 'do e <- System.Environment.getExecutablePath ; System.IO.putStr e'

[jhrcek]

That works ok

stack exec ghc -- -XNoImplicitPrelude -v0 -package-env=- -e 'do e <- System.Environment.getExecutablePath ; System.IO.putStr e'
/home/jhrcek/.stack/programs/x86_64-linux/ghc-tinfo6-8.10.7/lib/ghc-8.10.7/bin/ghc

[jhrcek]

Thank you very much for quick response. Works for me 👍

[michaelpj]

Worth a comment, very non-obvious that you're doing it this way to be compatible with NoImplicitPrelude.

Also, this probably won't work with RebindableSyntax still, but surely nobody sets that globally...

[hasufell]

RebindableSyntax

oh dear...