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ocamlPackages: Use lib.makeScope #53357

merged 1 commit into from
Jan 6, 2019


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@pukkamustard pukkamustard commented Jan 3, 2019

Motivation for this change

Simplify by using lib.makeScope (similar to #43104 and #33600).

Also stop exposing mkOcamlPackages as there is now a ocamlPackages.overrideScope' which can solve the use-case (#19605).

Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Determined the impact on package closure size (by running nix path-info -S before and after)
  • Assured whether relevant documentation is up to date
  • Fits

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vbgl commented Jan 5, 2019

Can you please explain how to override the OCaml compiler in the new setting (e.g., what to achieve what is described there: Thanks.

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Contributor Author

Can you please explain how to override the OCaml compiler in the new setting (e.g., what to achieve what is described there: Thanks.

oP = ocamlPackages.overrideScope' (self: super: {
    ocaml = super.ocaml.override { flambdaSupport = true; };

Things in ocamlPackages will be rebuilt with the overridden ocaml (if required).

A more complete example that uses nixpkgs overlays, overrides lwt4 and adds a custom OCaml package to ocamlPackages:

overlay = self: super: {
  ocamlPackages = super.ocamlPackages.overrideScope' (self: super: {

    ocaml = super.ocaml.override { flambdaSupport = true; };

    lwt4 = callPackage ./my_custom_lwt {};

    my_ocaml_package = callPackage ./my_ocaml_package {};



with <nixpkgs> {
  overlays = [ overlay ];

ocamlPackages.buildDunePackage rec {
  pname = "an-ocaml-project";
  version = "1.0";

  minimumOCamlVersion = "4.03";

  src = ./.;

  buildInputs = with ocamlPackages; [ utop ];
  propagatedBuildInputs = with ocamlPackages;
    [ cohttp-lwt my_ocaml_package ];


This will give a build environment with overridden OCaml compiler, a custom lwt version and a custom package. Any packages that require lwt (cohttp-lwt) will use the custom version.

@vbgl vbgl merged commit 9211bcc into NixOS:master Jan 6, 2019
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4 participants