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.Most Perl packages from CPAN are so straight-forward to build
that they are defined in pkgs/all-packages.nix
itself. Here is an example:
perlClassC3 = 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. As usual, you can test this package as follows:
$ nix-build -A perlClassC3
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 perlClassC3.)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 = ${db4}/include" >> config.in
'';
}
Dependencies on other Perl packages can be specified in the
buildInputs and
propagatedBuildInputs attributes. If something is
exclusively a build-time dependency, use
buildInputs; if it’s (also) a runtime dependency,
use propagatedBuildInputs. For instance, this
builds a Perl module that has runtime dependencies on a bunch of other
modules:
perlClassC3Componentised = buildPerlPackage rec {
name = "Class-C3-Componentised-1.0004";
src = fetchurl {
url = "mirror://cpan/authors/id/A/AS/ASH/${name}.tar.gz";
sha256 = "0xql73jkcdbq4q9m0b0rnca6nrlvf5hyzy8is0crdk65bynvs8q1";
};
propagatedBuildInputs = [
perlClassC3 perlClassInspector perlTestException perlMROCompat
];
};
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