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diff --git a/doc/languages-frameworks/perl.xml b/doc/languages-frameworks/perl.xml new file mode 100644 index 0000000000000..54b82f4a05601 --- /dev/null +++ b/doc/languages-frameworks/perl.xml @@ -0,0 +1,181 @@ +<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 { + 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"; + }; + }; +</screen> + +The output can be pasted into +<filename>pkgs/top-level/perl-packages.nix</filename> or wherever else +you need it.</para> + +</section> + +</section> + |