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
$out/nix-support/propagated-user-env-packages.
nix-env recursively installs all packages listed
in this file when you install a package that has it. This ensures
that a Perl package can find its dependencies.buildPerlPackage is built on top of
stdenv, so everything can be customised in the
usual way. For instance, the BerkeleyDB module has
a preConfigure hook to generate a configuration
file used by Makefile.PL:
{buildPerlPackage, fetchurl, db}:
buildPerlPackage rec {
name = "BerkeleyDB-0.36";
src = fetchurl {
url = "mirror://cpan/authors/id/P/PM/PMQS/${name}.tar.gz";
sha256 = "07xf50riarb60l1h6m2dqmql8q5dij619712fsgw7ach04d8g3z1";
};
preConfigure = ''
echo "LIB = ${db}/lib" > config.in
echo "INCLUDE = ${db}/include" >> config.in
'';
}
Dependencies on other Perl packages can be specified in the
buildInputs and
propagatedBuildInputs attributes. If something is
exclusively a build-time dependency, use
buildInputs; if it’s (also) a runtime dependency,
use propagatedBuildInputs. For instance, this
builds a Perl module that has runtime dependencies on a bunch of other
modules:
ClassC3Componentised = buildPerlPackage rec {
name = "Class-C3-Componentised-1.0004";
src = fetchurl {
url = "mirror://cpan/authors/id/A/AS/ASH/${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";
};
};
JavaAnt-based Java packages are typically built from source as follows:
stdenv.mkDerivation {
name = "...";
src = fetchurl { ... };
buildInputs = [ jdk ant ];
buildPhase = "ant";
}
Note that jdk is an alias for the OpenJDK.JAR files that are intended to be used by other packages should
be installed in $out/share/java. The OpenJDK has
a stdenv setup hook that adds any JARs in the
share/java directories of the build inputs to the
CLASSPATH environment variable. For instance, if the
package libfoo installs a JAR named
foo.jar in its share/java
directory, and another package declares the attribute
buildInputs = [ jdk libfoo ];
then CLASSPATH will be set to
/nix/store/...-libfoo/share/java/foo.jar.Private JARs
should be installed in a location like
$out/share/package-name.If your Java package provides a program, you need to generate a
wrapper script to run it using the OpenJRE. You can use
makeWrapper for this:
buildInputs = [ makeWrapper ];
installPhase =
''
mkdir -p $out/bin
makeWrapper ${jre}/bin/java $out/bin/foo \
--add-flags "-cp $out/share/java/foo.jar org.foo.Main"
'';
Note the use of jre, which is the part of the
OpenJDK package that contains the Java Runtime Environment. By using
${jre}/bin/java instead of
${jdk}/bin/java, you prevent your package from
depending on the JDK at runtime.It is possible to use a different Java compiler than
javac from the OpenJDK. For instance, to use the
Eclipse Java Compiler:
buildInputs = [ jre ant ecj ];
(Note that here you don’t need the full JDK as an input, but just the
JRE.) The ECJ has a stdenv setup hook that sets some environment
variables to cause Ant to use ECJ, but this doesn’t work with all Ant
files. Similarly, you can use the GNU Java Compiler:
buildInputs = [ gcj ant ];
Here, Ant will automatically use gij (the GNU Java
Runtime) instead of the OpenJRE.