Wrong nix parameters given to Stack

#1

After bumping GHC from “ghc8107” to “ghc924”, Stack is not working anymore.

It seems the way to add flags has changed. Here trying to generate a new cabal file:

$ stack hpack                                                                                                                                                                                       
stack: WARNING! Expecting stack options comment at line 1, column 1
stack: WARNING! Missing or unusable stack options specification
stack: WARNING! Using runghc without any additional stack options
Invalid argument `nix/stack-integration.nix'
Error executing interpreter command: stack --nix --no-nix-pure --nix-shell-file runghc -- nix/stack-integration.nix hpack

Stack version is “2.7.5 x86_64 hpack-0.34.7”, apparently it should be hpack 0.35 but I could not find a way to bump it.
I looked at Stack documentation to see if I could spot a format change in parameter but found nothing.

Any idea where to look please? Or even better, a fix!

Edit:
I tried a different order:

$ stack --nix --no-nix-pure --nix-shell-file nix/stack-integration.nix runghc -- hpack
Invalid option `--nix-shell-file'
#2

Do you have some way that someone else could reproduce the error you’re seeing?

A command like stack --nix --no-nix-pure --nix-shell-file nix/stack-integration.nix does seem like it should work. stack --nix-help does list --nix-shell-file as a valid argument, as least with stack-2.7.5.

I’d also suggest using the --verbose flag with stack, so that you can see the actual nix-shell command that stack will invoke under-the-hood.

#3

Thank you for your comments.
My mistake, I thought hpack was installed by default with Stack but it’s not the case, so it could not be found in the new version.
In the end I had to install it separately and call it directly.

1 Like
#4

Stack does not install Hpack, it is compiled with the Hpack library ‘built in’.

If you command (for example) stack build --dry-run and Stack finds a package.yaml file, it will re-create a Cabal file.

Command stack --hpack-numeric-version to discover what version of the Hpack library comes with your version of Stack. Stack 2.9.1 (coming very soon …), will use Hpack version 0.35.0.

Use stack --with-hpack <path_to_your_own_Hpack_executable> to use Stack with your own Hpack executable (for example stack --with-hpack hpack ... if Hpack is on your PATH).

2 Likes
#5

Thanks too, useful additions!

Particularly the --with-hpack option to run it in another context.