70 lines
2.9 KiB
Markdown
70 lines
2.9 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. It defines an (optional) attribute `minimumOCamlVersion` 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. It sets the `doCheck` (optional) attribute to `true` which means that tests will be run with `dune runtest -p angstrom` after the build (`dune build -p angstrom`) is complete. It uses `alcotest` as a build input (because it is 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.
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```nix
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{ lib
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, fetchFromGitHub
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, buildDunePackage
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, alcotest
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, result
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, bigstringaf
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}:
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buildDunePackage rec {
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pname = "angstrom";
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version = "0.10.0";
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minimumOCamlVersion = "4.03";
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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 = "0lh6024yf9ds0nh9i93r9m6p5psi8nvrqxl5x7jwl13zb0r9xfpw";
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};
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buildInputs = [ alcotest ];
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propagatedBuildInputs = [ bigstringaf result ];
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doCheck = true;
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meta = with lib; {
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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 = licenses.bsd3;
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maintainers = with maintainers; [ sternenseemann ];
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};
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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
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, fetchurl
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, buildDunePackage
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}:
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buildDunePackage rec {
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pname = "wtf8";
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version = "1.0.1";
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minimumOCamlVersion = "4.01";
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src = fetchurl {
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url = "https://github.com/flowtype/ocaml-${pname}/releases/download/v${version}/${pname}-${version}.tbz";
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sha256 = "1msg3vycd3k8qqj61sc23qks541cxpb97vrnrvrhjnqxsqnh6ygq";
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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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