nix: devShell for oxcaml

We add 3 new dev shells for OxCaml:

- bootstrap-ox: For testing the bootstrap process with OxCaml
- ox-minimal: For building dune with OxCaml and running the OxCaml test-cases
- ox: For attempting to build a dev shell with OxCaml

In order to do this, we need to fetch the latest patches from the OxCaml
opam repo, however not all of them can be applied to the package
versions found in nixpkgs. Because of this we cannot build a full
devShell, but we can get pretty close. The File nix/ox-patches.nix deals
with the fetching and application of the patches.

Signed-off-by: Ali Caglayan <[email protected]>

Author: Alizter

flake.lock

@@ -10,6 +10,14 @@
       url = "github:nix-ocaml/nix-overlays";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    oxcaml = {
+      url = "github:oxcaml/oxcaml";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    oxcaml-opam-repository = {
+      url = "github:oxcaml/opam-repository";
+      flake = false;
+    };
   };
   outputs =
     {
@@ -18,6 +26,8 @@
       nixpkgs,
       melange,
       ocaml-overlays,
+      oxcaml,
+      oxcaml-opam-repository,
     }:
     flake-utils.lib.eachDefaultSystem (
       system:
@@ -46,6 +56,13 @@
             });
           })
         ];
+        
+        applyOxcamlPatches = import ./nix/ox-patches.nix { 
+          inherit pkgs; 
+          lib = pkgs.lib; 
+          oxcamlOpamRepo = oxcaml-opam-repository;
+        };
+        
         dune-static-overlay = self: super: {
           ocamlPackages = super.ocaml-ng.ocamlPackages_5_3.overrideScope (
             oself: osuper: {
@@ -174,10 +191,29 @@
                 extraBuildInputs ? (pkgs: [ ]),
                 meta ? null,
                 duneFromScope ? false,
+                includeTestDeps ? true,
+                packageOverrides ? (oself: osuper: { }),
               }:
               let
+                hasOcamlOverride = (packageOverrides { } { ocaml = null; }) ? ocaml;
+                
                 pkgs' =
-                  if duneFromScope then
+                  if hasOcamlOverride then
+                    pkgs.extend (
+                      pself: psuper: {
+                        ocamlPackages = psuper.ocamlPackages.overrideScope (
+                          oself: osuper:
+                            (pkgs.lib.mapAttrs
+                              (name: pkg:
+                                if pkgs.lib.isDerivation pkg && pkg ? overrideAttrs
+                                then pkg.overrideAttrs (old: { doCheck = false; })
+                                else pkg)
+                              osuper)
+                            // (packageOverrides oself osuper)
+                        );
+                      }
+                    )
+                  else if duneFromScope then
                     pkgs.extend (
                       pself: psuper: {
                         ocamlPackages = psuper.ocamlPackages.overrideScope (
@@ -196,39 +232,45 @@
                   #!${stdenv.shell}
                   "$DUNE_SOURCE_ROOT"/_boot/dune.exe $@
                 '';
+
+                baseInputs = if includeTestDeps then (testNativeBuildInputs pkgs') ++ docInputs else [ ];
+                
+                ocamlLibs = if includeTestDeps then
+                  (with pkgs'.ocamlPackages; [
+                    ctypes
+                    cinaps
+                    integers
+                    lwt
+                    mdx
+                    menhir
+                    merlin
+                    ocaml-index
+                    ocaml-lsp
+                    odoc
+                    patdiff
+                    ppx_expect
+                    re
+                    spawn
+                    uutf
+                  ])
+                else
+                  [ ];
               in
 
               pkgs'.mkShell {
                 shellHook = ''
                   export DUNE_SOURCE_ROOT=$PWD
                 '';
                 inherit meta;
-                nativeBuildInputs = (testNativeBuildInputs pkgs') ++ docInputs ++ [ duneScript ];
-                inputsFrom = [ pkgs'.ocamlPackages.dune_3 ];
+                nativeBuildInputs = baseInputs ++ [ duneScript ] ++ (if hasOcamlOverride then [ pkgs'.ocamlPackages.ocaml ] else [ ]);
+                inputsFrom = if hasOcamlOverride then [ ] else [ pkgs'.ocamlPackages.dune_3 ];
                 buildInputs =
-                  testBuildInputs
-                  ++ (
-                    with pkgs'.ocamlPackages;
-                    [
-                      ctypes
-                      cinaps
-                      integers
-                      lwt
-                      mdx
-                      menhir
-                      merlin
-                      ocaml-index
-                      ocaml-lsp
-                      odoc
-                      patdiff
-                      ppx_expect
-                      re
-                      spawn
-                      uutf
-                    ]
-                    ++ (extraBuildInputs pkgs')
-                  );
+                  (if includeTestDeps then testBuildInputs else [ ])
+                  ++ ocamlLibs
+                  ++ (extraBuildInputs pkgs')
+                  ++ (if hasOcamlOverride then [ pkgs'.ocamlPackages.findlib ] else [ ]);
                 inherit INSIDE_NIX;
+                dontDetectOcamlConflicts = hasOcamlOverride;
               };
           in
           {
@@ -333,6 +375,56 @@
               '';
             };
 
+            bootstrap-ox = pkgs.mkShell {
+              inherit INSIDE_NIX;
+              buildInputs = [
+                pkgs.gnumake
+                oxcaml.packages.${system}.default
+              ];
+              meta.description = ''
+                Provides a minimal shell environment with OxCaml in order to
+                test the bootstrapping script.
+              '';
+            };
+
+            ox-minimal = makeDuneDevShell {
+              includeTestDeps = false;
+              packageOverrides = oself: osuper:
+                (applyOxcamlPatches oself osuper) // {
+                  # dune_3 = self.packages.${system}.default;
+                  ocaml = oxcaml.packages.${system}.default.overrideAttrs (old: {
+                    passthru = (old.passthru or { }) // pkgs.ocamlPackages.ocaml.passthru;
+                    meta = (old.meta or { }) // pkgs.ocamlPackages.ocaml.meta;
+                  });
+                  spawn = osuper.spawn.overrideAttrs (old: { doCheck = false; });
+                };
+              extraBuildInputs = pkgs: with pkgs.ocamlPackages; [
+                re
+                spawn
+                uutf
+                findlib
+              ];
+              meta.description = ''
+                Provides a minimal shell environment with OxCaml in order to
+                run the OxCaml tests.
+              '';
+            };
+
+            ox = makeDuneDevShell {
+              packageOverrides = oself: osuper:
+                (applyOxcamlPatches oself osuper) // {
+                  dune_3 = self.packages.${system}.default;
+                  ocaml = oxcaml.packages.${system}.default.overrideAttrs (old: {
+                    passthru = (old.passthru or { }) // pkgs.ocamlPackages.ocaml.passthru;
+                    meta = (old.meta or { }) // pkgs.ocamlPackages.ocaml.meta;
+                  });
+                };
+              meta.description = ''
+                Provides a full shell environment with the OxCaml compiler to
+                develop with Dune. Warning: does not work.
+              '';
+            };
+
             microbench = makeDuneDevShell {
               extraBuildInputs = pkgs: [
                 pkgs.ocamlPackages.core_bench