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The current example in the manual no longer builds, mainly because `useDune2 = true` is required, but also because the inputs have changed. The new examples are copied verbatim from nixpkgs.
94 lines
3.3 KiB
Markdown
94 lines
3.3 KiB
Markdown
# OCaml {#sec-language-ocaml}
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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`.
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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`.
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Here is a simple package example.
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- It defines an (optional) attribute `minimalOCamlVersion` that will be used to
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throw a descriptive evaluation error if building with an older OCaml is
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attempted.
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- It uses the `fetchFromGitHub` fetcher to get its source.
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- `useDune2 = true` ensures that the latest version of Dune is used for the
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build (this may become the default value in a future release).
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- It sets the optional `doCheck` attribute such that tests will be run with
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`dune runtest -p angstrom` after the build (`dune build -p angstrom`) is
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complete, but only if the Ocaml version is at at least `"4.05"`.
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- It uses the package `ocaml-syntax-shims` as a build input, `alcotest` and
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`ppx_let` as check inputs (because they are needed to run the tests), and
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`bigstringaf` and `result` as propagated build inputs (thus they will also be
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available to libraries depending on this library).
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- The library will be installed using the `angstrom.install` file that dune
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generates.
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```nix
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{ lib,
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fetchFromGitHub,
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buildDunePackage,
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ocaml,
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ocaml-syntax-shims,
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alcotest,
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result,
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bigstringaf,
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ppx_let }:
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buildDunePackage rec {
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pname = "angstrom";
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version = "0.15.0";
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useDune2 = true;
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minimalOCamlVersion = "4.04";
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src = fetchFromGitHub {
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owner = "inhabitedtype";
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repo = pname;
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rev = version;
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sha256 = "1hmrkdcdlkwy7rxhngf3cv3sa61cznnd9p5lmqhx20664gx2ibrh";
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};
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checkInputs = [ alcotest ppx_let ];
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buildInputs = [ ocaml-syntax-shims ];
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propagatedBuildInputs = [ bigstringaf result ];
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doCheck = lib.versionAtLeast ocaml.version "4.05";
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meta = {
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homepage = "https://github.com/inhabitedtype/angstrom";
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description = "OCaml parser combinators built for speed and memory efficiency";
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license = lib.licenses.bsd3;
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maintainers = with lib.maintainers; [ sternenseemann ];
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};
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```
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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.
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```nix
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{ lib, fetchurl, buildDunePackage }:
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buildDunePackage rec {
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pname = "wtf8";
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version = "1.0.2";
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useDune2 = true;
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minimalOCamlVersion = "4.02";
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src = fetchurl {
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url = "https://github.com/flowtype/ocaml-${pname}/releases/download/v${version}/${pname}-v${version}.tbz";
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sha256 = "09ygcxxd5warkdzz17rgpidrd0pg14cy2svvnvy1hna080lzg7vp";
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};
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meta = with lib; {
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homepage = "https://github.com/flowtype/ocaml-wtf8";
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description = "WTF-8 is a superset of UTF-8 that allows unpaired surrogates.";
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license = licenses.mit;
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maintainers = [ maintainers.eqyiel ];
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};
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}
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```
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