Haskell-language-server: ghc version could not be determined

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1

Hi, I am working with Obsidiansystems Obelisk and try to get the haskell-language-server running.

I am stuck with a somewhat frustrating detail. The hls doesn’t want to start, erroring out with

Found "/home/ruben/code/my-palantype/learn-palantype/hie.yaml" for "/home/ruben/code/my-palantype/learn-palantype/a"
Run entered for haskell-language-server-wrapper(haskell-language-server-wrapper) Version 1.6.1.0, Git revision f4022c5bb8530cd306c53b941878244bf27a5d41 (dirty) x86_64 ghc-8.10.7
Current directory: /home/ruben/code/my-palantype/learn-palantype
Operating system: linux
Arguments: ["--lsp","-d","-l","/run/user/1000/hls.log"]
Cradle directory: /home/ruben/code/my-palantype/learn-palantype
Cradle type: Cabal

Tool versions found on the $PATH
cabal:		3.8.1.0
stack:		2.9.1
ghc:		Not found


Consulting the cradle to get project GHC version...
Failed to get project GHC version:CradleError {cradleErrorDependencies = [], cradleErrorExitCode = ExitFailure 1, cradleErrorStderr = ["Error when calling cabal --builddir=/home/ruben/.cache/hie-bios/dist-learn-palantype-8a6791f81bf6f884398119cfc941c18b v2-exec --with-compiler /home/ruben/.cache/hie-bios/wrapper-13a09b18ea883dd377d59db5e821a86b ghc -v0 -- --numeric-version","","Error: cabal: The program 'ghc' version >=7.0.1 is required but the version of\n/home/ruben/.cache/hie-bios/wrapper-13a09b18ea883dd377d59db5e821a86b could not\nbe determined.\n\n"]}

Process lsp-haskell stderr finished

However, running the command in question in the terminal, works perfectly fine:

$ cabal --builddir=/home/ruben/.cache/hie-bios/dist-learn-palantype-8a6791f81bf6f884398119cfc941c18b v2-exec --with-compiler /home/ruben/.cache/hie-bios/wrapper-13a09b18ea883dd377d59db5e821a86b ghc -v0 -- --numeric-version
8.10.7

I am working on the development branch of Obelisk, to get GHC 8.10.7 and I am using easy-hls-nix to select the haskell-language-server for me. In the obelisk configuration this looks like this:

-- default.nix
  with pkgs.haskell.lib;
  obelisk.project ./. ({ ... }: {
    shellToolOverrides = self: super: {
      inherit easy-hls;
      inherit (pkgs) cabal-install;
      inherit (pkgs.haskell.compiler) ghc8107Binary;
    };
    -- ...
  })

This is why I am effectively using haskell-language-server version 1.6.1.0.

Also, note that I run a nix shell specific to obelisk projects

$ nix-shell -A shells.ghc

prior to starting emacs (which then tries to connect to hls) and also when testing hls outside of emacs.

2

Hi!

What Editor are you using, and are you making sure everything is correctly set up? It seems like there is no ghc on the $PATH. That’s per se not wrong, just curious.
Are you launching your editor of choice from the same context as your obelisk shell, such that GHC 8.10.7 and HLS is on your $PATH?

I assume you don’t have a cabal.project file, which would affect the results as well.

3

I am using emacs, and the setup is straightforward. I double-checked the configuration variables, but it’s a setup that generally works.

Yes, I don’t have ghc on path (using NixOS). Instead, it’s part of the shell that I am launching. I installed ghc independently just to be sure but it makes no difference.

Yes I am launching my editor from the nix-shell (that has ghc, haskell-language-server-wrapper) and from the same shell the offending command (which throws the error) works fine.

I have a cabal.project file:

optional-packages:
  *
write-ghc-environment-files: never
4

Ok, but there is something that doesn’t quite add up: If you launch emacs from the obelisk shell, then there is a GHC version on $PATH right? But HLS isn’t finding it?
When you launch hls-wrapper from the cli, does the same error occur? E.g. haskell-language-server-wrapper --debug <some-source-file>

5

Indeed it doesn’t add up.

I can run all these commands just fine (from inside the same shell where I start emacs):

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.10.7
$ haskell-language-server-wrapper --version
haskell-language-server version: 1.6.1.0 (GHC: 8.10.7) (PATH: /nix/store/f47pcsmzd94z7big4h6nwp5j2gkz5xz8-haskell-language-server-1.6.1.0-installer/bin/haskell-language-server-wrapper) (GIT hash: f4022c5bb8530cd306c53b941878244bf27a5d41)

And even the command that fails according to the log output of haskell-language-server within emacs:

$ cabal --builddir=/home/ruben/.cache/hie-bios/dist-learn-palantype-8a6791f81bf6f884398119cfc941c18b v2-exec --with-compiler /home/ruben/.cache/hie-bios/wrapper-13a09b18ea883dd377d59db5e821a86b ghc -v0 -- --numeric-version
8.10.7
6

I deleted hie.yaml and got a different error that seems to point into the right direction:

Failed to get project GHC version:CradleError {cradleErrorDependencies = [], cradleErrorExitCode = ExitFailure 127, cradleErrorStderr = ["Error when calling ghc --numeric-version","","/nix/store/dzrvibwj2vjwqmc34wk3x1ffsjpp4av7-bash-4.4-p23/bin/bash: symbol lookup error: /usr/lib/libc.so.6: undefined symbol: _dl_audit_symbind_alt, version GLIBC_PRIVATE\n"]}

There seems to be a problem with bash. Or, more specific: when emacs calls ghc --numeric-version, some broken bash is invoked. Or there is a mismatch between libc versions.

7

The cause could simply be that my haskell-language-server-wrapper is downloaded binary (from easy-hls-nix) and not built from source for NixOS.

8

So new question then:

Where in the depths of nixpkgs can I find the newest binary of haskell-language-server for GHC 8.10.7?

9

The bigger problem is to find the exact same ghc for obelisk to compile HLS with. I am afraid, I haven’t found a simple way so far.

My technique was to checkout HLS from source and install it manually with the exact ghc version used to compile obelisk, e.g. cabal install -w <nix-path-to-ghc-8.10.7-from-obelisk-shell> exe:haskell-language-server and then invoke my editor of choice (in this case VSCode) for my obelisk projects with exactly that HLS version.

10

Thanks for your help. I got it to work in the way that you described.

  • I checked out haskell-language-server locally.
  • Within my obelisk project: nix-shell -A shells.ghc (I don’t know the difference to ob shell btw)
  • cd into the haskell-language-server directory
  • cabal install
  • configured emacs/lsp-haskell to find the hls server executable at $HOME/.cabal/bin/haskell-language-server (the wrapper doesn’t work, weird)
  • enjoying now haskell-language-server 1.9.1.0 in all its glory in my obelisk project

Some notes:

I had to switch to the develop branch to obelisk and activate useGHC8107 = true.

Also, my obelisk setup is simplified really:

-- default.nix
  with pkgs.haskell.lib;
  obelisk.project ./. ({ ... }: {
    shellToolOverrides = self: super: {
      inherit (pkgs) cabal-install;
    };
    -- ...
  })

There is no need to specify a path to obelisk’s ghc. The one obelisk is using is the only one I have available when inside nix-shell -A shells.ghc or ob shell.

Note: I had to run cabal update before cabal install. But that was it. Thanks again. There are some stan findings that I have to check now. Oh boy! :stuck_out_tongue: