Add example of how to enable profiling for executables and libraries to docs

[codygman]

I think this is correct (my in progress build with *.p_o implies so at least):

pkgs.haskell-nix.project {
  # 'cleanGit' cleans a source directory based on the files known by git
  projectFileName = "cabal.project";
  src = pkgs.haskell-nix.haskellLib.cleanGit {
    name = "haskell-language-server";
    src = ./.;
  };
  modules = [
    { enableExecutableProfiling = true; }
  ];
  # For `cabal.project` based projects specify the GHC version to use.
  compiler-nix-name = "ghc884"; # Not used for `stack.yaml` based projects.
}

How does that work actually? If nothing is specified in any list of the module list the value applies to all?

[codygman]

It looks like this is going to do the trick for adding profiling to haskell-language-server installed via hls-nix:

(hls { version = "8.8.3"; }).exes.haskell-language-server.override(_: {enableExecutableProfiling = true;});

Full shell.nix

{...}:

let
  sources = import ./nix/sources.nix;
  pkgs = import sources.nixpkgs {};
  hls  = import sources.hls-nix;
  hsPkgs = import ./default.nix {};
  hlsWithProfilng = (hls { version = "8.8.3"; }).exes.haskell-language-server.override(_: {enableExecutableProfiling = true;});
in
  hsPkgs.shellFor {
    # Include only the *local* packages of your project.
    packages = ps: with ps; [
      mylib
    ];

    # Builds a Hoogle documentation index of all dependencies,
    # and provides a "hoogle" command to search the index.
    withHoogle = true;

    # You might want some extra tools in the shell (optional).

    # Some common tools can be added with the `tools` argument
    tools = { cabal = "3.2.0.0"; hlint = "2.2.11"; brittany = "0.12.1.1";};
    # See overlays/tools.nix for more details

    # Some you may need to get some other way.
    buildInputs = with pkgs.haskellPackages;
      [ hspec-discover stack ghcid pkgs.postgresql hlsWithProfilng ];

    # Prevents cabal from choosing alternate plans, so that
    # *all* dependencies are provided by Nix.
    exactDeps = true;
  }

[brprice]

I find that (at least, when using flakes) this (enableExecutableProfiling = true) is not a full solution.

Whilst it works to profile

• via nix run
• via cabal in a nix develop shell when there are no (non-boot) external dependencies

It does not work to profile via cabal in a nix develop shell when there are external dependencies (ghc complains that Could not find module ‘Data.HashMap.Lazy’ Perhaps you haven't installed the profiling libraries for package ‘unordered-containers-0.2.14.0’?)

To get profiling-via-cabal working, I found it sufficed to have

modules = [
    { enableExecutableProfiling = true;
      enableLibraryProfiling = true;
    }
  ];

(In the future, it seems that just adding profiling: True to cabal.project should work: see #887. However, it is currently broken. )

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.