Support for specific programming languages The standard build environment makes it easy to build typical Autotools-based packages with very little code. Any other kind of package can be accomodated by overriding the appropriate phases of stdenv. However, there are specialised functions in Nixpkgs to easily build packages for other programming languages, such as Perl or Haskell. These are described in this chapter.
Perl Nixpkgs provides a function buildPerlPackage, a generic package builder function for any Perl package that has a standard Makefile.PL. It’s implemented in pkgs/development/perl-modules/generic. Perl packages from CPAN are defined in pkgs/perl-packages.nix, rather than pkgs/all-packages.nix. Most Perl packages are so straight-forward to build that they are defined here directly, rather than having a separate function for each package called from perl-packages.nix. However, more complicated packages should be put in a separate file, typically in pkgs/development/perl-modules. Here is an example of the former: ClassC3 = buildPerlPackage rec { name = "Class-C3-0.21"; src = fetchurl { url = "mirror://cpan/authors/id/F/FL/FLORA/${name}.tar.gz"; sha256 = "1bl8z095y4js66pwxnm7s853pi9czala4sqc743fdlnk27kq94gz"; }; }; Note the use of mirror://cpan/, and the ${name} in the URL definition to ensure that the name attribute is consistent with the source that we’re actually downloading. Perl packages are made available in all-packages.nix through the variable perlPackages. For instance, if you have a package that needs ClassC3, you would typically write foo = import ../path/to/foo.nix { inherit stdenv fetchurl ...; inherit (perlPackages) ClassC3; }; in all-packages.nix. You can test building a Perl package as follows: $ nix-build -A perlPackages.ClassC3 buildPerlPackage adds perl- to the start of the name attribute, so the package above is actually called perl-Class-C3-0.21. So to install it, you can say: $ nix-env -i perl-Class-C3 (Of course you can also install using the attribute name: nix-env -i -A perlPackages.ClassC3.) So what does buildPerlPackage do? It does the following: In the configure phase, it calls perl Makefile.PL to generate a Makefile. You can set the variable makeMakerFlags to pass flags to Makefile.PL It adds the contents of the PERL5LIB environment variable to #! .../bin/perl line of Perl scripts as -Idir flags. This ensures that a script can find its dependencies. In the fixup phase, it writes the propagated build inputs (propagatedBuildInputs) to the file $out/nix-support/propagated-user-env-packages. nix-env recursively installs all packages listed in this file when you install a package that has it. This ensures that a Perl package can find its dependencies. buildPerlPackage is built on top of stdenv, so everything can be customised in the usual way. For instance, the BerkeleyDB module has a preConfigure hook to generate a configuration file used by Makefile.PL: {buildPerlPackage, fetchurl, db4}: buildPerlPackage rec { name = "BerkeleyDB-0.36"; src = fetchurl { url = "mirror://cpan/authors/id/P/PM/PMQS/${name}.tar.gz"; sha256 = "07xf50riarb60l1h6m2dqmql8q5dij619712fsgw7ach04d8g3z1"; }; preConfigure = '' echo "LIB = ${db4}/lib" > config.in echo "INCLUDE = ${db4}/include" >> config.in ''; } Dependencies on other Perl packages can be specified in the buildInputs and propagatedBuildInputs attributes. If something is exclusively a build-time dependency, use buildInputs; if it’s (also) a runtime dependency, use propagatedBuildInputs. For instance, this builds a Perl module that has runtime dependencies on a bunch of other modules: ClassC3Componentised = buildPerlPackage rec { name = "Class-C3-Componentised-1.0004"; src = fetchurl { url = "mirror://cpan/authors/id/A/AS/ASH/${name}.tar.gz"; sha256 = "0xql73jkcdbq4q9m0b0rnca6nrlvf5hyzy8is0crdk65bynvs8q1"; }; propagatedBuildInputs = [ ClassC3 ClassInspector TestException MROCompat ]; };
Python Python packages that use setuptools, which many Python packages do nowadays, can be built very simply using the buildPythonPackage function. This function is implemented in pkgs/development/python-modules/generic/default.nix and works similarly to buildPerlPackage. (See for details.) Python packages that use buildPythonPackage are defined in pkgs/top-level/python-packages.nix. Most of them are simple. For example: twisted = buildPythonPackage { name = "twisted-8.1.0"; src = fetchurl { url = http://tmrc.mit.edu/mirror/twisted/Twisted/8.1/Twisted-8.1.0.tar.bz2; sha256 = "0q25zbr4xzknaghha72mq57kh53qw1bf8csgp63pm9sfi72qhirl"; }; propagatedBuildInputs = [ pkgs.ZopeInterface ]; meta = { homepage = http://twistedmatrix.com/; description = "Twisted, an event-driven networking engine written in Python"; license = "MIT"; }; };
Java Java packages should install JAR files in $out/lib/java.