nix:在pybind11中覆盖doCheck

时间:2019-06-12 09:07:49

标签: nix

看着https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/pybind11/default.nix,在我看来,我应该能够避免运行带有以下内容的测试(即设置-DPYBIND11_TEST=OFF):

pybind11 = pkgs.pybind11.overrideAttrs (oldAttrs: rec {
   doCheck = false;
});

但是,这不起作用。

我通过直接修改cmakeFlags解决了我的问题:

  pybind11 = pkgs.pybind11.overrideAttrs (oldAttrs: rec {
      cmakeFlags = [
        "-DPYTHON_EXECUTABLE=${pkgs.python.interpreter}"
        "-DPYBIND11_TEST=OFF"
      ];
  });

但是我想知道为什么前一种方法不起作用。

1 个答案:

答案 0 :(得分:1)

它不起作用,因为派生使用的是rec关键字,该关键字没有覆盖的概念。摘录:

{ stdenv, fetchurl, fetchFromGitHub, cmake, catch, python, eigen }:

stdenv.mkDerivation rec { #0
  name = "pybind-${version}";
  version = "2.2.4";

  doCheck = true; #1

  cmakeFlags = [ 
    "-DPYBIND11_TEST=${if doCheck then "ON" else "OFF"}"
  ];
}

使用.overrideAttrs (oldAttrs: { doCheck = false; })时,您仅覆盖doCheck属性,而不覆盖cmakeFlags,该属性仍从引入的词汇范围引用doCheck#1)由rec {}#0

因此,以下内容等同于上面的代码段:

{ stdenv, fetchurl, fetchFromGitHub, cmake, catch, python, eigen }:

stdenv.mkDerivation (let #0
  name = "pybind-${version}";
  version = "2.2.4";

  doCheck = true; #1

  cmakeFlags = [ 
    "-DPYBIND11_TEST=${if doCheck then "ON" else "OFF"}"
  ];
in { #0
  name = name;
  version = version;
  doCheck = doCheck; #1
  cmakeFlags = cmakeFlags;
}

mkDerivation只能看到它获得的attrset,而不能自省和修改构建该attrset的表达式。这是必需的Nix语言设计原则,因为它使您可以推理代码并启用惰性。 rec语义根本不适合覆盖。