Re: GHC packages' inputs leak in guix shell

[Saku Laesvuori <saku@laesvuori.fi>]

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On Mon, Aug 28, 2023 at 01:40:14PM +0200, Simon Tournier wrote:
> Hi,
> 
> On Thu, 24 Aug 2023 at 19:16, Saku Laesvuori <saku@laesvuori.fi> wrote:
> >> > Running `guix shell --pure ghc-esqueleto -D ghc-bytestring-builder`
> >> > results in an environment that has the base64-bytestring package (from
> >> > ghc-base64-bytestring) visible, even though it is not listed on listed
> >> > the command line (ghc-bytestring-builder doesn't dependend on it). It
> >> > seems to "leak" from the inputs of ghc-esqueleto which does depend on
> >> > ghc-base64-bytestring.
> >> 
> >> What do you mean by “leak”?
> >
> > I would expect packages to keep their (non-propagated) inputs separate
> > from the environment I use. Here ghc-esqueleto makes it's haskell inputs
> > visible to the ghc in my environment.
> 
> Could you be more explicit?
> 
> The package ghc-base64-bytestring does not seems being propagated; the
> store item ghc-base64-bytestring does not appear in the profile
> generated by “guix shell”.

Yes, it is not propagated but it's still visible to ghc, which is not
something I would expect. I'd expect to not be able to import modules
from packages that are not in any of the active profiles.

> However,
> 
> --8<---------------cut here---------------start------------->8---
> $ guix shell -C ghc-esqueleto ghc gcc-toolchain -- ghci
> GHCi, version 9.2.5: https://www.haskell.org/ghc/  :? for help
> ghci> import Data.ByteString.Base64.URL.Lazy
> ghci> :t encode
> encode
>   :: Data.ByteString.Lazy.Internal.ByteString
>      -> Data.ByteString.Lazy.Internal.ByteString
> --8<---------------cut here---------------end--------------->8---
> 
> and instead, you would like:
> 
>     <no location info>: error:
>         Could not find module `Data.ByteString.Base64.URL.Lazy'
>         It is not a module in the current program, or in any known package.
> 
> Right?

Exactly.

> Well, I do not know if it is possible.  I guess it is because of this
> file:
> 
> --8<---------------cut here---------------start------------->8---
> $ find $(guix build ghc-esqueleto) -type f -print | grep base64
> /gnu/store/zqax59v1v537h26g0kypka6klaaahnqf-ghc-esqueleto-3.5.8.1/lib/ghc-9.2.5/ghc-esqueleto-3.5.8.1.conf.d/base64-bytestring-1.2.1.0-CQYLTs5ShsEFl2lwe4hRrI.conf
> --8<---------------cut here---------------end--------------->8---

I think that is most likely the reason. I don't think cabal has this
problem (I haven't actually used cabal much at all so this is just
speculation), so it could be possible to fix. Of course, cabal-install
and guix have different ways of packaging so it might also be
impossible.

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