From dbfd26724defe3f8a63431e0fe1bf6955cc2f44f Mon Sep 17 00:00:00 2001 From: Guillaume Girol Date: Tue, 16 Nov 2021 16:49:17 +0000 Subject: [PATCH] doc: add ocaml end user doc to nixpkgs manual (#145100) doc: add ocaml end user doc to nixpkgs manual Co-authored-by: Sandro Co-authored-by: Dmitry Kalinkin --- doc/languages-frameworks/ocaml.section.md | 26 +++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/doc/languages-frameworks/ocaml.section.md b/doc/languages-frameworks/ocaml.section.md index 5ffc23173d6d..d266a032268c 100644 --- a/doc/languages-frameworks/ocaml.section.md +++ b/doc/languages-frameworks/ocaml.section.md @@ -1,5 +1,31 @@ # OCaml {#sec-language-ocaml} +## User guide {#sec-language-ocaml-user-guide} + +OCaml libraries are available in attribute sets of the form `ocaml-ng.ocamlPackages_X_XX` where X is to be replaced with the desired compiler version. For example, ocamlgraph compiled with OCaml 4.12 can be found in `ocaml-ng.ocamlPackages_4_12.ocamlgraph`. The compiler itself is also located in this set, under the name `ocaml`. + +If you don't care about the exact compiler version, `ocamlPackages` is a top-level alias pointing to a recent version of OCaml. + +OCaml applications are usually available top-level, and not inside `ocamlPackages`. Notable exceptions are build tools that must be built with the same compiler version as the compiler you intend to use like `dune` or `ocaml-lsp`. + +To open a shell able to build a typical OCaml project, put the dependencies in `buildInputs` and add `ocamlPackages.ocaml` and `ocamlPackages.findlib` to `nativeBuildInputs` at least. +For example: +```nix +let + pkgs = import {}; + # choose the ocaml version you want to use + ocamlPackages = pkgs.ocaml-ng.ocamlPackages_4_12; +in +pkgs.mkShell { + # build tools + nativeBuildInputs = with ocamlPackages; [ ocaml findlib dune_2 ocaml-lsp ]; + # dependencies + buildInputs = with ocamlPackages; [ ocamlgraph ]; +} +``` + +## Packaging guide {#sec-language-ocaml-packaging} + OCaml libraries should be installed in `$(out)/lib/ocaml/${ocaml.version}/site-lib/`. Such directories are automatically added to the `$OCAMLPATH` environment variable when building another package that depends on them or when opening a `nix-shell`. Given that most of the OCaml ecosystem is now built with dune, nixpkgs includes a convenience build support function called `buildDunePackage` that will build an OCaml package using dune, OCaml and findlib and any additional dependencies provided as `buildInputs` or `propagatedBuildInputs`.