unmet availability conditions: 'enable-ocaml-beta-repository'

[kentookura]

I maintain the flake for this project:

https://git.sr.ht/~jonsterling/ocaml-forester

It stopped working after some packages were updated, and I haven't been able to figure out how to fix it:

resolve> [ERROR] No solution including optional dependencies for forester.3.0.0 & ocaml-system:   * Incompatible packages:
resolve>             - forester >= 3.0.0 -> eio_main >= 0.13 -> eio_linux >= 0.13 -> eio >= 0.13 -> ocaml >= 5.1.0 -> ocaml-base-compiler >= 5.1.0~
resolve>             - ocaml-system
resolve>           * Missing dependency:
resolve>             - forester >= 3.0.0 -> eio_main >= 0.13 -> eio_linux >= 0.13 -> eio >= 0.13 -> ocaml >= 5.1.0 -> ocaml-variants < 5.1.1~ -> ocaml-beta
resolve>             unmet availability conditions: 'enable-ocaml-beta-repository'

To Reproduce

nix run sourcehut:~jonsterling/ocaml-forester for the original breakage. After cloning and updating the flake, nix build -L results in the same error

Expected behavior It builds

Environment

• 24.05.20231222.6df37dc (Uakari)
• Version of the code: (Do you mean version of opam-nix? latest)

[kentookura]

I tracked down the breaking commit to this one, which updates Eio

[balsoft]

It seems the main issue is the ocaml-system = "*" constraint, combined with the fact that the ocaml compiler in your nixpkgs version is not recent enough. Updating opam-repository (so that the compiler version in question is out of beta) and removing this constraint seems to make it build, although you will have to build the ocaml compiler yourself (shouldn't take too long, ~ 4 minutes on my hardware).

The complete diff that makes it work for me is this:

diff --git a/flake.lock b/flake.lock
index dc0ac51..813d188 100644
--- a/flake.lock
+++ b/flake.lock
@@ -140,11 +140,11 @@
     "opam-repository_2": {
       "flake": false,
       "locked": {
-        "lastModified": 1699845376,
-        "narHash": "sha256-RZ+w6CI/K1PO33D5H7mTK0pT4jDh6DzwMT3zSUOsWTo=",
+        "lastModified": 1703856811,
+        "narHash": "sha256-dE+PZI0N8Hahs+D8GuvYktBGPhW9cyBZGxN6K+n2Y1g=",
         "owner": "ocaml",
         "repo": "opam-repository",
-        "rev": "cd93eb224789c7c645f72575b685eec97b0ccbca",
+        "rev": "91155d8f7ba41238a91fbffd093e5bb7a532aa0a",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 35052b0..255c339 100644
--- a/flake.nix
+++ b/flake.nix
@@ -23,7 +23,7 @@
           let inherit (opam-nix.lib.${system}) buildOpamProject;
             scope = buildOpamProject
               { repos = [ "${opam-repository}" ]; } "forester" ./.
-              { ocaml-system = "*"; };
+              { };
           in
           scope;
         packages.default = self.legacyPackages.${system}."forester";

[kentookura]

This is fine for now, thanks!