devbox add ghc && devbox add haskellPackages.aeson does not add aeson to ghc package database about devbox

[loreto]

Thanks for reporting, let me take a look this coming week and see if we can easily fix it.

[Lagoja]

Confirmed this is still an issue. I think @ParetoOptimalDev is right that the solution is to rewrite haskellPackages to haskellPackages.ghcWithPackages. I think the implementation would be similar to what we do for PHP Extensions:

https://github.com/hezhizhen/devbox/blob/d71daf33f52a83ce33cf66d7461d59030403b49f/internal/planner/languages/php/php_v2_planner.go#L40

[ParetoOptimalDev]

Thanks for reporting, let me take a look this coming week and see if we can easily fix it.

Sure, if it helps my first thought was "Can devbox add haskellPackages.aeson just always rewrite to implicitly be equivalent to nix-shell -p "haskellPackages.ghcWithPackages (p: [p.aeson])" rather than what I'm assuming it's now equivalent to nix-shell -p haskellPackages.aeson.

For haskell in particular this is very useful because the built packages are cached. For things like the cryptonite library that take a long time to compile, this can save you hours.

Where as with the binary cache of cryptonite I can get ghci with cryptonite available in 3.8s:

$ time nix-shell -p "haskellPackages.ghcWithPackages (p: [p.cryptonite])" --run exit
... snip ... 
copying path '/nix/store/nkhj0j7vnvv0810g8zg15fpabvkwlzwy-memory-0.15.0' from 'https://cache.nixos.org'...
copying path '/nix/store/lyll680sx4cpbm2ivabq3abmhyc4z13q-cryptonite-0.29' from 'https://cache.nixos.org'...
building '/nix/store/dw00lxfnhhjnyfip8p6kd20ypcc4248s-ghc-8.10.7-with-packages.drv'...