From 15f220b07ced65b6ca8ed862249bf180b5ace9ca Mon Sep 17 00:00:00 2001
From: Vincent Laporte <Vincent.Laporte@gmail.com>
Date: Wed, 16 Mar 2022 17:30:39 +0100
Subject: [PATCH] ocamlPackages.buildDunePackage: add support for dune 3

---
 pkgs/build-support/ocaml/dune.nix | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/pkgs/build-support/ocaml/dune.nix b/pkgs/build-support/ocaml/dune.nix
index 18e8784cfab..f82bac7d199 100644
--- a/pkgs/build-support/ocaml/dune.nix
+++ b/pkgs/build-support/ocaml/dune.nix
@@ -1,8 +1,11 @@
-{ lib, stdenv, ocaml, findlib, dune_1, dune_2 }:
+{ lib, stdenv, ocaml, findlib, dune_1, dune_2, dune_3 }:
 
 { pname, version, nativeBuildInputs ? [], enableParallelBuilding ? true, ... }@args:
 
-let Dune = if args.useDune2 or true then dune_2 else dune_1; in
+let Dune =
+  let dune-version = args . duneVersion or (if args.useDune2 or true then "2" else "1"); in
+  { "1" = dune_1; "2" = dune_2; "3" = dune_3; }."${dune-version}"
+; in
 
 if (args ? minimumOCamlVersion && ! lib.versionAtLeast ocaml.version args.minimumOCamlVersion) ||
    (args ? minimalOCamlVersion && ! lib.versionAtLeast ocaml.version args.minimalOCamlVersion)
@@ -31,7 +34,7 @@ stdenv.mkDerivation ({
     runHook postInstall
   '';
 
-} // (builtins.removeAttrs args [ "minimalOCamlVersion" ]) // {
+} // (builtins.removeAttrs args [ "minimalOCamlVersion" "duneVersion" ]) // {
 
   name = "ocaml${ocaml.version}-${pname}-${version}";