Command to print `GHC_PACKAGE_PATH`

[sgraf812]

There should really be a command to just print GHC_PACKAGE_PATH as set by cabal exec, like stack path --ghc-package-path. Or is there already a way to do this right now?

[phadej]

Doens't something like

cabal exec -- sh -c 'echo $GHC_PACKAGE_PATH'

work?

[sgraf812]

This doesn't work on Windows. Well, it works when going through stack exec --no-ghc-package-path -- cabal exec -- sh -c 'echo $GHC_PACKAGE_PATH', but not when just doing cabal exec -- sh -c 'echo $GHC_PACKAGE_PATH' through a vanilla HP installation.

[phadej]

@sgraf812 note that (If i read code right) cabal exec doesn't always set GHC_PACKAGE_PATH, one scenario is when there is sandboxes involved (maybe stack triggers something like that in cabal, dunno).

What are you trying to do, maybe there is some other way to solve your X problem, without solving Y (= getting GHC_PACKAGE_PATH)?

[sgraf812]

I'm basically trying to solve https://stackoverflow.com/questions/46505007/access-ghc-package-database-in-test-and-benchmark-suite in a relatively portable way.

[phadej]

@sgraf812 one solution is to use build-type: Custom, in a way http://hackage.haskell.org/package/cabal-doctest does, so you get all needed flags.

With doctest, we have to feed doctest package-ids and package-db flags, for it to work properly. cabal-doctest "solves" that. The core problem seems similar. I'm not aware of easier, non-hacky solution. (Except adding custom code into Cabal)

[sgraf812]

OK, thanks. I'll look into it when I prepare a release for my prototype.

[23Skidoo]

#3643 is possibly related.

[gbaz]

possibly could be solved by #7500 ?

[jneira]

This doesn't work on Windows. Well, it works when going through stack exec --no-ghc-package-path -- cabal exec -- sh -c 'echo $GHC_PACKAGE_PATH', but not when just doing cabal exec -- sh -c 'echo $GHC_PACKAGE_PATH' through a vanilla HP installation.

Hi, i usually use this trick to print the environment vars set by cabal:

PS D:\dev\ws\haskell\cabal> cabal exec -- cmd
Microsoft Windows [Versión 10.0.19044.1645]
(c) Microsoft Corporation. Todos los derechos reservados.

D:\dev\ws\haskell\cabal>echo %GHC_ENVIRONMENT%
D:\dev\ws\haskell\cabal\dist-newstyle\tmp\environment.-10396\.ghc.environment.x86_64-mingw32-8.10.7

Note i am not using %GHC_PACKAGE_PATH% as nowadays cabal exec is cabal v2-exec and it seems the v2 use ghc environment files to interact with ghc instead GHC_PACKAGE_PATH. But if it was set, it would be also printed
In fact v1-commands are deprecated and v1-exec does not exist anymore in cabal-3.6.2.0

So as there was a suggestion to fix your original issue, motivation to print GHC_PACKAGE_PATH i would close this.
Feel free to reopen if you have any question or you think it should be keep alive.