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diff --git a/doc/languages-frameworks/ocaml.section.md b/doc/languages-frameworks/ocaml.section.md new file mode 100644 index 00000000000..5ffc23173d6 --- /dev/null +++ b/doc/languages-frameworks/ocaml.section.md @@ -0,0 +1,93 @@ +# OCaml {#sec-language-ocaml} + +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`. + +Here is a simple package example. + +- It defines an (optional) attribute `minimalOCamlVersion` that will be used to + throw a descriptive evaluation error if building with an older OCaml is + attempted. + +- It uses the `fetchFromGitHub` fetcher to get its source. + +- `useDune2 = true` ensures that the latest version of Dune is used for the + build (this may become the default value in a future release). + +- It sets the optional `doCheck` attribute such that tests will be run with + `dune runtest -p angstrom` after the build (`dune build -p angstrom`) is + complete, but only if the Ocaml version is at at least `"4.05"`. + +- It uses the package `ocaml-syntax-shims` as a build input, `alcotest` and + `ppx_let` as check inputs (because they are needed to run the tests), and + `bigstringaf` and `result` as propagated build inputs (thus they will also be + available to libraries depending on this library). + +- The library will be installed using the `angstrom.install` file that dune + generates. + +```nix +{ lib, + fetchFromGitHub, + buildDunePackage, + ocaml, + ocaml-syntax-shims, + alcotest, + result, + bigstringaf, + ppx_let }: + +buildDunePackage rec { + pname = "angstrom"; + version = "0.15.0"; + useDune2 = true; + + minimalOCamlVersion = "4.04"; + + src = fetchFromGitHub { + owner = "inhabitedtype"; + repo = pname; + rev = version; + sha256 = "1hmrkdcdlkwy7rxhngf3cv3sa61cznnd9p5lmqhx20664gx2ibrh"; + }; + + checkInputs = [ alcotest ppx_let ]; + buildInputs = [ ocaml-syntax-shims ]; + propagatedBuildInputs = [ bigstringaf result ]; + doCheck = lib.versionAtLeast ocaml.version "4.05"; + + meta = { + homepage = "https://github.com/inhabitedtype/angstrom"; + description = "OCaml parser combinators built for speed and memory efficiency"; + license = lib.licenses.bsd3; + maintainers = with lib.maintainers; [ sternenseemann ]; + }; +``` + +Here is a second example, this time using a source archive generated with `dune-release`. It is a good idea to use this archive when it is available as it will usually contain substituted variables such as a `%%VERSION%%` field. This library does not depend on any other OCaml library and no tests are run after building it. + +```nix +{ lib, fetchurl, buildDunePackage }: + +buildDunePackage rec { + pname = "wtf8"; + version = "1.0.2"; + + useDune2 = true; + + minimalOCamlVersion = "4.02"; + + src = fetchurl { + url = "https://github.com/flowtype/ocaml-${pname}/releases/download/v${version}/${pname}-v${version}.tbz"; + sha256 = "09ygcxxd5warkdzz17rgpidrd0pg14cy2svvnvy1hna080lzg7vp"; + }; + + meta = with lib; { + homepage = "https://github.com/flowtype/ocaml-wtf8"; + description = "WTF-8 is a superset of UTF-8 that allows unpaired surrogates."; + license = licenses.mit; + maintainers = [ maintainers.eqyiel ]; + }; +} +``` |