86af88d7c4
This provides an up-to-date illustration of how `nix-generate-from-cpan` generates packages.
182 lines
6.2 KiB
XML
182 lines
6.2 KiB
XML
<section xmlns="http://docbook.org/ns/docbook"
|
||
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||
xml:id="sec-language-perl">
|
||
|
||
<title>Perl</title>
|
||
|
||
<para>Nixpkgs provides a function <varname>buildPerlPackage</varname>,
|
||
a generic package builder function for any Perl package that has a
|
||
standard <varname>Makefile.PL</varname>. It’s implemented in <link
|
||
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/perl-modules/generic"><filename>pkgs/development/perl-modules/generic</filename></link>.</para>
|
||
|
||
<para>Perl packages from CPAN are defined in <link
|
||
xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/perl-packages.nix"><filename>pkgs/top-level/perl-packages.nix</filename></link>,
|
||
rather than <filename>pkgs/all-packages.nix</filename>. 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 <filename>perl-packages.nix</filename>. However, more
|
||
complicated packages should be put in a separate file, typically in
|
||
<filename>pkgs/development/perl-modules</filename>. Here is an
|
||
example of the former:
|
||
|
||
<programlisting>
|
||
ClassC3 = buildPerlPackage rec {
|
||
name = "Class-C3-0.21";
|
||
src = fetchurl {
|
||
url = "mirror://cpan/authors/id/F/FL/FLORA/${name}.tar.gz";
|
||
sha256 = "1bl8z095y4js66pwxnm7s853pi9czala4sqc743fdlnk27kq94gz";
|
||
};
|
||
};
|
||
</programlisting>
|
||
|
||
Note the use of <literal>mirror://cpan/</literal>, and the
|
||
<literal>${name}</literal> 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
|
||
<filename>all-packages.nix</filename> through the variable
|
||
<varname>perlPackages</varname>. For instance, if you have a package
|
||
that needs <varname>ClassC3</varname>, you would typically write
|
||
|
||
<programlisting>
|
||
foo = import ../path/to/foo.nix {
|
||
inherit stdenv fetchurl ...;
|
||
inherit (perlPackages) ClassC3;
|
||
};
|
||
</programlisting>
|
||
|
||
in <filename>all-packages.nix</filename>. You can test building a
|
||
Perl package as follows:
|
||
|
||
<screen>
|
||
$ nix-build -A perlPackages.ClassC3
|
||
</screen>
|
||
|
||
<varname>buildPerlPackage</varname> adds <literal>perl-</literal> to
|
||
the start of the name attribute, so the package above is actually
|
||
called <literal>perl-Class-C3-0.21</literal>. So to install it, you
|
||
can say:
|
||
|
||
<screen>
|
||
$ nix-env -i perl-Class-C3
|
||
</screen>
|
||
|
||
(Of course you can also install using the attribute name:
|
||
<literal>nix-env -i -A perlPackages.ClassC3</literal>.)</para>
|
||
|
||
<para>So what does <varname>buildPerlPackage</varname> do? It does
|
||
the following:
|
||
|
||
<orderedlist>
|
||
|
||
<listitem><para>In the configure phase, it calls <literal>perl
|
||
Makefile.PL</literal> to generate a Makefile. You can set the
|
||
variable <varname>makeMakerFlags</varname> to pass flags to
|
||
<filename>Makefile.PL</filename></para></listitem>
|
||
|
||
<listitem><para>It adds the contents of the <envar>PERL5LIB</envar>
|
||
environment variable to <literal>#! .../bin/perl</literal> line of
|
||
Perl scripts as <literal>-I<replaceable>dir</replaceable></literal>
|
||
flags. This ensures that a script can find its
|
||
dependencies.</para></listitem>
|
||
|
||
<listitem><para>In the fixup phase, it writes the propagated build
|
||
inputs (<varname>propagatedBuildInputs</varname>) to the file
|
||
<filename>$out/nix-support/propagated-user-env-packages</filename>.
|
||
<command>nix-env</command> recursively installs all packages listed
|
||
in this file when you install a package that has it. This ensures
|
||
that a Perl package can find its dependencies.</para></listitem>
|
||
|
||
</orderedlist>
|
||
|
||
</para>
|
||
|
||
<para><varname>buildPerlPackage</varname> is built on top of
|
||
<varname>stdenv</varname>, so everything can be customised in the
|
||
usual way. For instance, the <literal>BerkeleyDB</literal> module has
|
||
a <varname>preConfigure</varname> hook to generate a configuration
|
||
file used by <filename>Makefile.PL</filename>:
|
||
|
||
<programlisting>
|
||
{ buildPerlPackage, fetchurl, db }:
|
||
|
||
buildPerlPackage rec {
|
||
name = "BerkeleyDB-0.36";
|
||
|
||
src = fetchurl {
|
||
url = "mirror://cpan/authors/id/P/PM/PMQS/${name}.tar.gz";
|
||
sha256 = "07xf50riarb60l1h6m2dqmql8q5dij619712fsgw7ach04d8g3z1";
|
||
};
|
||
|
||
preConfigure = ''
|
||
echo "LIB = ${db}/lib" > config.in
|
||
echo "INCLUDE = ${db}/include" >> config.in
|
||
'';
|
||
}
|
||
</programlisting>
|
||
|
||
</para>
|
||
|
||
<para>Dependencies on other Perl packages can be specified in the
|
||
<varname>buildInputs</varname> and
|
||
<varname>propagatedBuildInputs</varname> attributes. If something is
|
||
exclusively a build-time dependency, use
|
||
<varname>buildInputs</varname>; if it’s (also) a runtime dependency,
|
||
use <varname>propagatedBuildInputs</varname>. For instance, this
|
||
builds a Perl module that has runtime dependencies on a bunch of other
|
||
modules:
|
||
|
||
<programlisting>
|
||
ClassC3Componentised = buildPerlPackage rec {
|
||
name = "Class-C3-Componentised-1.0004";
|
||
src = fetchurl {
|
||
url = "mirror://cpan/authors/id/A/AS/ASH/${name}.tar.gz";
|
||
sha256 = "0xql73jkcdbq4q9m0b0rnca6nrlvf5hyzy8is0crdk65bynvs8q1";
|
||
};
|
||
propagatedBuildInputs = [
|
||
ClassC3 ClassInspector TestException MROCompat
|
||
];
|
||
};
|
||
</programlisting>
|
||
|
||
</para>
|
||
|
||
<section xml:id="ssec-generation-from-CPAN"><title>Generation from CPAN</title>
|
||
|
||
<para>Nix expressions for Perl packages can be generated (almost)
|
||
automatically from CPAN. This is done by the program
|
||
<command>nix-generate-from-cpan</command>, which can be installed
|
||
as follows:</para>
|
||
|
||
<screen>
|
||
$ nix-env -i nix-generate-from-cpan
|
||
</screen>
|
||
|
||
<para>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:
|
||
|
||
<screen>
|
||
$ nix-generate-from-cpan XML::Simple
|
||
XMLSimple = buildPerlPackage rec {
|
||
name = "XML-Simple-2.22";
|
||
src = fetchurl {
|
||
url = "mirror://cpan/authors/id/G/GR/GRANTM/${name}.tar.gz";
|
||
sha256 = "b9450ef22ea9644ae5d6ada086dc4300fa105be050a2030ebd4efd28c198eb49";
|
||
};
|
||
propagatedBuildInputs = [ XMLNamespaceSupport XMLSAX XMLSAXExpat ];
|
||
meta = {
|
||
description = "An API for simple XML files";
|
||
license = with stdenv.lib.licenses; [ artistic1 gpl1Plus ];
|
||
};
|
||
};
|
||
</screen>
|
||
|
||
The output can be pasted into
|
||
<filename>pkgs/top-level/perl-packages.nix</filename> or wherever else
|
||
you need it.</para>
|
||
|
||
</section>
|
||
|
||
</section>
|
||
|