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https://github.com/NixOS/nixpkgs.git
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334 lines
11 KiB
XML
334 lines
11 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xml:id="chap-language-support">
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<title>Support for specific programming languages</title>
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<para>The <link linkend="chap-stdenv">standard build
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environment</link> makes it easy to build typical Autotools-based
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packages with very little code. Any other kind of package can be
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accomodated by overriding the appropriate phases of
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<literal>stdenv</literal>. However, there are specialised functions
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in Nixpkgs to easily build packages for other programming languages,
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such as Perl or Haskell. These are described in this chapter.</para>
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<section xml:id="ssec-language-perl"><title>Perl</title>
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<para>Nixpkgs provides a function <varname>buildPerlPackage</varname>,
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a generic package builder function for any Perl package that has a
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standard <varname>Makefile.PL</varname>. It’s implemented in <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/perl-modules/generic"><filename>pkgs/development/perl-modules/generic</filename></link>.</para>
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<para>Perl packages from CPAN are defined in <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/perl-packages.nix"><filename>pkgs/top-level/perl-packages.nix</filename></link>,
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rather than <filename>pkgs/all-packages.nix</filename>. Most Perl
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packages are so straight-forward to build that they are defined here
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directly, rather than having a separate function for each package
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called from <filename>perl-packages.nix</filename>. However, more
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complicated packages should be put in a separate file, typically in
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<filename>pkgs/development/perl-modules</filename>. Here is an
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example of the former:
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<programlisting>
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ClassC3 = buildPerlPackage rec {
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name = "Class-C3-0.21";
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src = fetchurl {
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url = "mirror://cpan/authors/id/F/FL/FLORA/${name}.tar.gz";
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sha256 = "1bl8z095y4js66pwxnm7s853pi9czala4sqc743fdlnk27kq94gz";
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};
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};
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</programlisting>
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Note the use of <literal>mirror://cpan/</literal>, and the
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<literal>${name}</literal> in the URL definition to ensure that the
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name attribute is consistent with the source that we’re actually
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downloading. Perl packages are made available in
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<filename>all-packages.nix</filename> through the variable
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<varname>perlPackages</varname>. For instance, if you have a package
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that needs <varname>ClassC3</varname>, you would typically write
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<programlisting>
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foo = import ../path/to/foo.nix {
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inherit stdenv fetchurl ...;
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inherit (perlPackages) ClassC3;
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};
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</programlisting>
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in <filename>all-packages.nix</filename>. You can test building a
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Perl package as follows:
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<screen>
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$ nix-build -A perlPackages.ClassC3
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</screen>
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<varname>buildPerlPackage</varname> adds <literal>perl-</literal> to
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the start of the name attribute, so the package above is actually
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called <literal>perl-Class-C3-0.21</literal>. So to install it, you
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can say:
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<screen>
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$ nix-env -i perl-Class-C3
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</screen>
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(Of course you can also install using the attribute name:
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<literal>nix-env -i -A perlPackages.ClassC3</literal>.)</para>
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<para>So what does <varname>buildPerlPackage</varname> do? It does
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the following:
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<orderedlist>
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<listitem><para>In the configure phase, it calls <literal>perl
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Makefile.PL</literal> to generate a Makefile. You can set the
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variable <varname>makeMakerFlags</varname> to pass flags to
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<filename>Makefile.PL</filename></para></listitem>
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<listitem><para>It adds the contents of the <envar>PERL5LIB</envar>
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environment variable to <literal>#! .../bin/perl</literal> line of
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Perl scripts as <literal>-I<replaceable>dir</replaceable></literal>
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flags. This ensures that a script can find its
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dependencies.</para></listitem>
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<listitem><para>In the fixup phase, it writes the propagated build
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inputs (<varname>propagatedBuildInputs</varname>) to the file
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<filename>$out/nix-support/propagated-user-env-packages</filename>.
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<command>nix-env</command> recursively installs all packages listed
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in this file when you install a package that has it. This ensures
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that a Perl package can find its dependencies.</para></listitem>
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</orderedlist>
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</para>
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<para><varname>buildPerlPackage</varname> is built on top of
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<varname>stdenv</varname>, so everything can be customised in the
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usual way. For instance, the <literal>BerkeleyDB</literal> module has
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a <varname>preConfigure</varname> hook to generate a configuration
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file used by <filename>Makefile.PL</filename>:
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<programlisting>
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{buildPerlPackage, fetchurl, db}:
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buildPerlPackage rec {
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name = "BerkeleyDB-0.36";
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src = fetchurl {
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url = "mirror://cpan/authors/id/P/PM/PMQS/${name}.tar.gz";
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sha256 = "07xf50riarb60l1h6m2dqmql8q5dij619712fsgw7ach04d8g3z1";
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};
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preConfigure = ''
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echo "LIB = ${db}/lib" > config.in
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echo "INCLUDE = ${db}/include" >> config.in
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'';
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}
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</programlisting>
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</para>
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<para>Dependencies on other Perl packages can be specified in the
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<varname>buildInputs</varname> and
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<varname>propagatedBuildInputs</varname> attributes. If something is
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exclusively a build-time dependency, use
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<varname>buildInputs</varname>; if it’s (also) a runtime dependency,
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use <varname>propagatedBuildInputs</varname>. For instance, this
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builds a Perl module that has runtime dependencies on a bunch of other
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modules:
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<programlisting>
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ClassC3Componentised = buildPerlPackage rec {
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name = "Class-C3-Componentised-1.0004";
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src = fetchurl {
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url = "mirror://cpan/authors/id/A/AS/ASH/${name}.tar.gz";
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sha256 = "0xql73jkcdbq4q9m0b0rnca6nrlvf5hyzy8is0crdk65bynvs8q1";
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};
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propagatedBuildInputs = [
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ClassC3 ClassInspector TestException MROCompat
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];
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};
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</programlisting>
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</para>
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<section><title>Generation from CPAN</title>
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<para>Nix expressions for Perl packages can be generated (almost)
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automatically from CPAN. This is done by the program
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<command>nix-generate-from-cpan</command>, which can be installed
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as follows:</para>
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<screen>
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$ nix-env -i nix-generate-from-cpan
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</screen>
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<para>This program takes a Perl module name, looks it up on CPAN,
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fetches and unpacks the corresponding package, and prints a Nix
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expression on standard output. For example:
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<screen>
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$ nix-generate-from-cpan XML::Simple
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XMLSimple = buildPerlPackage {
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name = "XML-Simple-2.20";
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src = fetchurl {
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url = mirror://cpan/authors/id/G/GR/GRANTM/XML-Simple-2.20.tar.gz;
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sha256 = "5cff13d0802792da1eb45895ce1be461903d98ec97c9c953bc8406af7294434a";
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};
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propagatedBuildInputs = [ XMLNamespaceSupport XMLSAX XMLSAXExpat ];
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meta = {
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description = "Easily read/write XML (esp config files)";
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license = "perl";
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};
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};
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</screen>
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The output can be pasted into
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<filename>pkgs/top-level/perl-packages.nix</filename> or wherever else
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you need it.</para>
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</section>
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</section>
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<section><title>Python</title>
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<para>
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Python packages that
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use <link xlink:href="http://pypi.python.org/pypi/setuptools/"><literal>setuptools</literal></link>,
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which many Python packages do nowadays, can be built very simply using
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the <varname>buildPythonPackage</varname> function. This function is
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implemented
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in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/python-modules/generic/default.nix"><filename>pkgs/development/python-modules/generic/default.nix</filename></link>
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and works similarly to <varname>buildPerlPackage</varname>. (See
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<xref linkend="ssec-language-perl"/> for details.)
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</para>
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<para>
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Python packages that use <varname>buildPythonPackage</varname> are
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defined
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in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/python-packages.nix"><filename>pkgs/top-level/python-packages.nix</filename></link>.
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Most of them are simple. For example:
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<programlisting>
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twisted = buildPythonPackage {
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name = "twisted-8.1.0";
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src = fetchurl {
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url = http://tmrc.mit.edu/mirror/twisted/Twisted/8.1/Twisted-8.1.0.tar.bz2;
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sha256 = "0q25zbr4xzknaghha72mq57kh53qw1bf8csgp63pm9sfi72qhirl";
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};
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propagatedBuildInputs = [ pkgs.ZopeInterface ];
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meta = {
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homepage = http://twistedmatrix.com/;
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description = "Twisted, an event-driven networking engine written in Python";
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license = "MIT";
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};
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};
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</programlisting>
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</para>
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</section>
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<section xml:id="ssec-language-java"><title>Java</title>
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<para>Ant-based Java packages are typically built from source as follows:
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<programlisting>
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stdenv.mkDerivation {
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name = "...";
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src = fetchurl { ... };
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buildInputs = [ jdk ant ];
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buildPhase = "ant";
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}
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</programlisting>
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Note that <varname>jdk</varname> is an alias for the OpenJDK.</para>
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<para>JAR files that are intended to be used by other packages should
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be installed in <filename>$out/share/java</filename>. The OpenJDK has
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a stdenv setup hook that adds any JARs in the
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<filename>share/java</filename> directories of the build inputs to the
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<envar>CLASSPATH</envar> environment variable. For instance, if the
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package <literal>libfoo</literal> installs a JAR named
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<filename>foo.jar</filename> in its <filename>share/java</filename>
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directory, and another package declares the attribute
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<programlisting>
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buildInputs = [ jdk libfoo ];
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</programlisting>
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then <envar>CLASSPATH</envar> will be set to
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<filename>/nix/store/...-libfoo/share/java/foo.jar</filename>.</para>
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<para>Private JARs
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should be installed in a location like
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<filename>$out/share/<replaceable>package-name</replaceable></filename>.</para>
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<para>If your Java package provides a program, you need to generate a
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wrapper script to run it using the OpenJRE. You can use
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<literal>makeWrapper</literal> for this:
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<programlisting>
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buildInputs = [ makeWrapper ];
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installPhase =
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''
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mkdir -p $out/bin
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makeWrapper ${jre}/bin/java $out/bin/foo \
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--add-flags "-cp $out/share/java/foo.jar org.foo.Main"
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'';
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</programlisting>
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Note the use of <literal>jre</literal>, which is the part of the
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OpenJDK package that contains the Java Runtime Environment. By using
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<literal>${jre}/bin/java</literal> instead of
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<literal>${jdk}/bin/java</literal>, you prevent your package from
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depending on the JDK at runtime.</para>
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<para>It is possible to use a different Java compiler than
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<command>javac</command> from the OpenJDK. For instance, to use the
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Eclipse Java Compiler:
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<programlisting>
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buildInputs = [ jre ant ecj ];
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</programlisting>
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(Note that here you don’t need the full JDK as an input, but just the
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JRE.) The ECJ has a stdenv setup hook that sets some environment
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variables to cause Ant to use ECJ, but this doesn’t work with all Ant
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files. Similarly, you can use the GNU Java Compiler:
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<programlisting>
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buildInputs = [ gcj ant ];
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</programlisting>
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Here, Ant will automatically use <command>gij</command> (the GNU Java
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Runtime) instead of the OpenJRE.</para>
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</section>
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<!--
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<section><title>Haskell</title>
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<para>TODO</para>
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</section>
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<section><title>TeX / LaTeX</title>
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<para>* Special support for building TeX documents</para>
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</section>
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-->
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</chapter>
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