fix: Return a user errormessage when OCAMLFIND_CONF unset / no ocamlf…

…ind in PATH

Signed-off-by: Antonio Nuno Monteiro <[email protected]>

src/dune_rules/context.ml

@@ -298,17 +298,27 @@ module Build_environment_kind = struct
           | Some s -> Opam2_environment s
           | None -> Unknown)))
 
-  let findlib_paths ocamlfind ~kind ~context ~findlib_toolchain ~env ~dir =
+  let findlib_paths ocamlfind ~kind ~findlib_toolchain ~env ~dir =
     match (ocamlfind, query ~kind ~findlib_toolchain ~env) with
     | ( Some ocamlfind
       , ( Cross_compilation_using_findlib_toolchain _
         | Opam2_environment _
         | Unknown ) ) -> Ocamlfind.conf_path ocamlfind
-    | None, Cross_compilation_using_findlib_toolchain _toolchain ->
-      Code_error.raise
-        "Could not find ocamlfind in PATH or an environment variable \
-         OCAMLFIND_CONF"
-        [ ("context", Context_name.to_dyn context) ]
+    | None, Cross_compilation_using_findlib_toolchain toolchain ->
+      User_error.raise
+        [ Pp.textf
+            "Could not find ocamlfind in PATH or an environment variable \
+             `OCAMLFIND_CONF' while cross-compiling with toolchain `%s'"
+            (Context_name.to_string toolchain)
+        ]
+        ~hints:
+          [ Pp.enumerate
+              [ "`opam install ocamlfind' and/or:"
+              ; "Point `OCAMLFIND_CONF' to the findlib configuration that \
+                 defines this toolchain"
+              ]
+              ~f:Pp.text
+          ]
     | _, Hardcoded_path l ->
       List.map l ~f:Path.of_filename_relative_to_initial_cwd
     | None, Opam2_environment opam_prefix ->
@@ -413,7 +423,7 @@ let create ~(kind : Kind.t) ~path ~env ~env_nodes ~name ~merlin ~targets
     in
     let build_dir = Context_name.build_dir name in
     let default_ocamlpath =
-      Build_environment_kind.findlib_paths ocamlfind ~kind ~context:name ~env
+      Build_environment_kind.findlib_paths ocamlfind ~kind ~env
         ~findlib_toolchain ~dir
     in
     let ocaml_config_ok_exn = function

test/blackbox-tests/test-cases/custom-cross-compilation/no-ocamlfind-in-path.t

@@ -0,0 +1,43 @@
+Dune shows an error message when ocamlfind isn't in PATH and OCAMLFIND_CONF
+isn't set
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.7)
+  > (package (name repro))
+  > EOF
+  $ cat > dune <<EOF
+  > (executable
+  >  (name gen)
+  >  (modules gen)
+  >  (enabled_if
+  >   (= %{context_name} "default"))
+  >  (libraries libdep))
+  > (rule
+  >  (with-stdout-to
+  >   gen.ml
+  >   (echo "let () = Format.printf \"let x = 1\"")))
+  > (library
+  >  (name repro)
+  >  (public_name repro)
+  >  (modules foo))
+  > EOF
+
+  $ mkdir ocaml-bin
+  $ cat > ocaml-bin/ocamlc <<EOF
+  > #!/usr/bin/env sh
+  > export PATH="\$ORIG_PATH"
+  > exec ocamlc "\$@"
+  > EOF
+  $ chmod +x ocaml-bin/ocamlc
+
+  $ DUNE_PATH=$(dirname `which dune`)
+  $ SH_PATH=$(dirname `which sh`)
+  $ env ORIG_PATH="$PATH" PATH="$SH_PATH:$DUNE_PATH:$PWD/ocaml-bin" dune build @install -x foo
+  Error: Could not find ocamlfind in PATH or an environment variable
+  `OCAMLFIND_CONF' while cross-compiling with toolchain `foo'
+  Hint:
+  - `opam install ocamlfind' and/or:
+  - Point `OCAMLFIND_CONF' to the findlib configuration that defines this
+    toolchain
+  [1]
+