Support for specific programming languagesThe 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.PerlNixpkgs 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/top-level/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.PLIt 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
];
};
Generation from CPANNix expressions for Perl packages can be generated (almost)
automatically from CPAN. This is done by the program
nix-generate-from-cpan, which can be installed
as follows:
$ nix-env -i nix-generate-from-cpan
This program takes a Perl module name, looks it up on CPAN,
fetches and unpacks the corresponding package, and prints a Nix
expression on standard output. For example:
$ nix-generate-from-cpan XML::Simple
XMLSimple = buildPerlPackage {
name = "XML-Simple-2.20";
src = fetchurl {
url = mirror://cpan/authors/id/G/GR/GRANTM/XML-Simple-2.20.tar.gz;
sha256 = "5cff13d0802792da1eb45895ce1be461903d98ec97c9c953bc8406af7294434a";
};
propagatedBuildInputs = [ XMLNamespaceSupport XMLSAX XMLSAXExpat ];
meta = {
description = "Easily read/write XML (esp config files)";
license = "perl";
};
};
The output can be pasted into
pkgs/top-level/perl-packages.nix or wherever else
you need it.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";
};
};
JavaJava packages should install JAR files in
$out/lib/java.