Failing to build a dune project

[wereHamster]

https://github.com/dmtrKovalenko/odiff

I know nothing about ocaml and dune. I'm just trying to package this project with Nix so that can manage this dependency with Nix.

The flake.nix I have now is copied straight from the docs:

{
  description = "The fastest image difference tool in the world";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    opam-nix.url = "github:tweag/opam-nix";
  };

  outputs = { self, opam-nix, flake-utils }:
      flake-utils.lib.eachDefaultSystem (system:
        with opam-nix.lib.${system}; {
          defaultPackage = (buildDuneProject { } "odiff" ./. { }).odiff;
        });
}

When building it I'm getting this error:

error: builder for '/nix/store/dpwzsm01qbvhqmki2zq33mhbbabjxh4h-odiff-io-3.2.0.drv' failed with exit code 1;
       last 25 log lines:
       > File "io/tiff/dune", lines 16-19, characters 0-118:
       > 16 | (rule
       > 17 |  (targets tiff_flags.sexp tiff_c_flags.sexp tiff_c_library_flags.sexp)
       > 18 |  (action
       > 19 |   (run ../config/discover.exe)))
       > (cd _build/default/io/tiff && ../config/discover.exe)
       > Fatal error: exception Not_found
       > File "io/png/dune", lines 16-19, characters 0-115:
       > 16 | (rule
       > 17 |  (targets png_flags.sexp png_c_flags.sexp png_c_library_flags.sexp)
       > 18 |  (action
       > 19 |   (run ../config/discover.exe)))
       > (cd _build/default/io/png && ../config/discover.exe)
       > Fatal error: exception Not_found
       > File "io/png_write/dune", lines 15-21, characters 0-139:
       > 15 | (rule
       > 16 |  (targets
       > 17 |   png_write_flags.sexp
       > 18 |   png_write_c_flags.sexp
       > 19 |   png_write_c_library_flags.sexp)
       > 20 |  (action
       > 21 |   (run ../config/discover.exe)))
       > (cd _build/default/io/png_write && ../config/discover.exe)
       > Fatal error: exception Not_found
       >

Maybe the project is doing something fancy that is outside of a standard ocaml / dune setup? I found this code which seems to be related to the error:

https://github.com/dmtrKovalenko/odiff/blob/49ccd5d15c3a0956eca2effc3812716d5ef2d67e/io/png_write/dune#L15-L21

https://github.com/dmtrKovalenko/odiff/blob/49ccd5d15c3a0956eca2effc3812716d5ef2d67e/io/config/discover.ml

Any hints how to package odiff with Nix flakes are highly appreciated. Thanks.

[balsoft]

I think it just can't find the needed libraries, and one of them isn't even in nixpkgs. I'll investigate further later.