@michalrus, thanks for your PR! By analyzing the history of the files in this pull request, we identified @peti, @mdorman and @pikajude to be potential reviewers.

@shlevy, here’s a first sketch of the README → https://github.com/michalrus/intero-nix-shim#readme

It feels too complicated. :/

@michalrus So does intero-nix-shim just call out to ghc in $PATH?

I’ve been wondering about that, but finally decided to do:

https://github.com/michalrus/intero-nix-shim/blob/520c73fce1dee7bf0cc3fd007c636eda538b4d91/src/Main.hs#L30-L37

So ghci is cabal repl. Any other exec is run via cabal exec (including ghc, see below for command-line args parsing). There are two more commands needed, one returning project’s root dir, and another with its compilation targets.

Feel free to change anything in that initial sketch, I’ve just given you RW access, but it works for me. ^_^

Hmm... I don't know if I love that. What if I don't have cabal-install?

Me neither, but then it would be really hard to determine GHCi’s (Intero’s) real arguments. :(

Cabal adds a lot. Once intero is running, you can see that in htop or ps or …

We’d need to duplicate their work to determine them.

Can we hard-code a reference to cabal-install into intero-nix-shim?

Nice idea! But it’d also be desirable to hard-code intero itself, right?

It would simplify users’ default.nixes. =]

Yep!

I’m on it!

BTW, it may be interesting to look at intero-nix-shim-with-packages that doesn't have to rebuild a cabal dist dir in-tree

@shlevy, paths symlinked to libexec/{cabal,intero} and hardcoded. =)

Also, the README is updated accordingly. It’s simpler now! https://github.com/michalrus/intero-nix-shim#readme

I might need some help with that first build job failing… =( The other two are 🍏 .

Which build job?

This PR on Travis → https://travis-ci.org/NixOS/nixpkgs/builds/221563087

Oh, travis is pure noise.

@peti any objection here?

Do we really need import-from-derivation here? This feature has several unpleasant side-effects in Nix/Hydra today and I'd rather not use it for a package that Hydra is going to discover and build.

Ah, missed that. @michalrus Can you check in the cabal2nix expr?

Sure, whatever is necessary! I just didn’t want to commit auto-generated code, but if it’s needed, sure.

Where should I put it? Or… should I splice it straight into configuration-common.nix?

Could you point me to some issues/docs to read about these side effects? This seems interesting.

@peti any preference for where it should live?

(I’ll be offline for a few days, so if we don’t finish today, and you want it finished today/tomorrow, don’t hesitate to take this over :) ).

Bump. =]

@peti ping? @michalrus I'll find a place for it in a few days if there's nothing from @peti

@shlevy, thank you! 🙇‍♂️ In the meantime, I modified README not to disorient users.

@michalrus Can you just create an intero-nix-shim.nix here with the cabal2nix results?

@shlevy, is this better? =) I followed the ../tools/haskell/ approach from Haste/Tinc in that same file.

Thank you! :)

Cherry-picked onto 17.03: a162c6c