How to have a properly setup haskell-language-server in nix-shell?

[abailly]

Disclaimer: I am a total noob when it comes to nix + Haskell setup.

In order to learn how to use nix with Haskell, I have tried adding nix configuration to an existing simple package: https://github.com/abailly/hydra-sim/blob/master/shell.nix following the tutorial here: https://input-output-hk.github.io/haskell.nix/tutorials/getting-started/
After some fiddling I managed to have nix-build building the package, and nix-shell dropping me into a properly configured shell. However, I am struggling with configuration of haskell-language-server, more specifically to get the correct version which should be HLS for 8.10.2 (the compile version defined in default.nix).
I have tried to configure it following https://haskell4nix.readthedocs.io/nixpkgs-users-guide.html?highlight=language%20server#how-to-install-haskell-language-server with some adaptation:

    buildInputs = with pkgs.haskellPackages;
      [ ghcid
        haskell-language-server.override { supportedGhcVersions = [ "8102" ]; }
      ];

but to no avail. What am I missing?

[rvl]

The haskell4nix docs apply to the standard nixpkgs Haskell infrastructure, and not Haskell.nix.

Add haskell-language-server = "0.8.0"; to the shellFor tools attrset.
It will use the ghc version matching the project.

[abailly]

Thanks a lot @rvl! Did I miss something in the documentation I should have paid more attention to? Is there a way to know which tools are available? I am happy to help on proposing a documentation PR if this can help someone else.

[rvl]

tools is a shortcut way of getting the executable from any package on hackage (plus a few special ones like haskell-language-server).

There is a shellFor reference here: https://input-output-hk.github.io/haskell.nix/reference/library/#shellfor, but more user-guide-type documentation might help.

[abailly]

plus a few special ones like haskell-language-server

That's probably the part which might cause confusion to unwary users like myself. Is there a place that could be linked to listing those special packages?

[hamishmack]

That's probably the part which might cause confusion to unwary users like myself. Is there a place that could be linked to listing those special packages?

Only custom-tools are haskell-language-server and an old branch of ghcide that we should really remove. I don't think we want to add more of these, better just to make sure things are put in hackage.

[abailly]

OK. One last snag I am hitting is that haskell-language-server-wrapper is not installed as part of the haskell-language-server installation. Am I missing something? The hls-wrapper is needed for proper IDE (Emacs in my case) integration.

[hamishmack]

Added #1015 to fix the -wrapper issue. Also haskell-language-server is in hackage now!

[abailly]

Great! So does this mean i can install it elsewhere than from the tools? Then I guess it will come naturally with the wrapper Le dim. 24 janv. 2021 à 11:55, Hamish Mackenzie <notifications@github.com> a écrit :

…

Added #1015 <#1015> to fix the -wrapper issue. Also haskell-language-server is in hackage now! — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1012 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAJ2HJCZMCRAWNR5Q6V2BTS3P4BFANCNFSM4WNFQJPA> .

[hamishmack]

Something like this should work now (with the current haskell.nix master):

project.shellFor {
  buildInputs = builtins.attrValues
    (haskell-nix.hackage-package {
      compiler-nix-name = "ghc8103";
      name = "haskell-language-server";
      version = "latest";
    }).components.exes;
}

With #1015 these will also work:

project.shellFor {
  tools = {
    haskell-language-server = "latest";
    haskell-language-server-wrapper = "latest";
  };
}

project.shellFor {
  buildInputs = [
    (haskell-nix.tool "ghc8103" "haskell-language-server" "latest")
    (haskell-nix.tool "ghc8103" "haskell-language-server-wrapper" "latest")
  ];
}

[abailly]

Awesome! I am afk but will give a try as soon as I can. Then I will only have to figure out how to configure properly lsp-haskell in emacs :) Le dim. 24 janv. 2021 à 12:15, Hamish Mackenzie <notifications@github.com> a écrit :

…

Something like this should work now (with the current haskell.nix master): project.shellFor { buildInputs = builtins.attrValues (haskell-nix.hackage-package { compiler-nix-name = "ghc8103"; name = "haskell-language-server"; version = "latest"; }).components.exes; } With #1015 <#1015> these will also work: project.shellFor { tools = { haskell-language-server = "latest"; haskell-language-server-wrapper = "latest"; }; } project.shellFor { buildInputs = [ (haskell-nix.tool "ghc8103" "haskell-language-server" "latest") (haskell-nix.tool "ghc8103" "haskell-language-server-wrapper" "latest") ]; } — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1012 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAJ2HPUTUV44YAMZK7USXTS3P6ODANCNFSM4WNFQJPA> .

[abailly]

So I tried the first solution

    # Some you may need to get some other way.
    buildInputs = builtins.attrValues
      (haskellNix.hackage-package {
          compiler-nix-name = "ghc8102";
          name = "haskell-language-server";
          version = "latest";
        }).components.exes;

and it says

trace: No index state specified for hydra-sim, using the latest index state that we know about (2021-01-20T00:00:00Z)!
trace: To make project.plan-nix for hoogle a fixed-output derivation but not materialized, set `plan-sha256` to the output of the 'calculateMaterializedSha' script in 'passthru'.
trace: To materialize project.plan-nix for hoogle entirely, pass a writable path as the `materialized` argument and run the 'updateMaterialized' script in 'passthru'.
error: attribute 'hackage-package' missing, at /home/curry/hydra-sim/shell.nix:26:8
(use '--show-trace' to show detailed location information)

I guess I will have to wait for #1015 to reach master?

[TerrorJack]

Feel free to borrow the shell.nix from one of our own projects, the lines to set up haskell-language-server is here :)

[abailly]

Thanks to the kind help from quite a few people I managed to solve that issue. I now have a working environment with emacs, LSP, HLS and Nix working together! There are still a few glitches and lot of stuff I don't really understand but at least I can load a file in Emacs and have the HLS installed in nix-shell give me errors and hints.
The result lives here: https://github.com/abailly/hydra-sim/