<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="chap-language-support"> <title>Support for specific programming languages</title> <para>The <link linkend="chap-stdenv">standard build environment</link> 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 <literal>stdenv</literal>. 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.</para> <section 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> <section xml:id="sec-python"><title>Python</title> <para> Currently supported interpreters are <varname>python26</varname>, <varname>python27</varname>, <varname>python32</varname>, <varname>python33</varname>, <varname>python34</varname> and <varname>pypy</varname>. </para> <para> <varname>python</varname> is an alias of <varname>python27</varname> and <varname>python3</varname> is an alias of <varname>python34</varname>. </para> <para> <varname>python26</varname> and <varname>python27</varname> do not include modules that require external dependencies (to reduce dependency bloat). Following modules need to be added as <varname>buildInput</varname> explicitly: </para> <itemizedlist> <listitem><para><varname>python.modules.bsddb</varname></para></listitem> <listitem><para><varname>python.modules.curses</varname></para></listitem> <listitem><para><varname>python.modules.curses_panel</varname></para></listitem> <listitem><para><varname>python.modules.crypt</varname></para></listitem> <listitem><para><varname>python.modules.gdbm</varname></para></listitem> <listitem><para><varname>python.modules.sqlite3</varname></para></listitem> <listitem><para><varname>python.modules.tkinter</varname></para></listitem> <listitem><para><varname>python.modules.readline</varname></para></listitem> </itemizedlist> <para>For convenience <varname>python27Full</varname> and <varname>python26Full</varname> are provided with all modules included.</para> <para> Python packages that use <link xlink:href="http://pypi.python.org/pypi/setuptools/"><literal>setuptools</literal></link> or <literal>distutils</literal>, can be built using the <varname>buildPythonPackage</varname> function as documented below. </para> <para> All packages depending on any Python interpreter get appended <varname>$out/${python.libPrefix}/site-packages</varname> to <literal>$PYTHONPATH</literal> if such directory exists. </para> <variablelist> <title> Useful attributes on interpreters packages: </title> <varlistentry> <term><varname>libPrefix</varname></term> <listitem><para> Name of the folder in <literal>${python}/lib/</literal> for corresponding interpreter. </para></listitem> </varlistentry> <varlistentry> <term><varname>interpreter</varname></term> <listitem><para> Alias for <literal>${python}/bin/${executable}.</literal> </para></listitem> </varlistentry> <varlistentry> <term><varname>buildEnv</varname></term> <listitem><para> Function to build python interpreter environments with extra packages bundled together. See <xref linkend="ssec-python-build-env" /> for usage and documentation. </para></listitem> </varlistentry> <varlistentry> <term><varname>sitePackages</varname></term> <listitem><para> Alias for <literal>lib/${libPrefix}/site-packages</literal>. </para></listitem> </varlistentry> <varlistentry> <term><varname>executable</varname></term> <listitem><para> Name of the interpreter executable, ie <literal>python3.4</literal>. </para></listitem> </varlistentry> </variablelist> <section xml:id="ssec-build-python-package"><title><varname>buildPythonPackage</varname> function</title> <para> The function is implemented 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>. Example usage: <programlisting language="nix"> twisted = buildPythonPackage { name = "twisted-8.1.0"; src = pkgs.fetchurl { url = http://tmrc.mit.edu/mirror/twisted/Twisted/8.1/Twisted-8.1.0.tar.bz2; sha256 = "0q25zbr4xzknaghha72mq57kh53qw1bf8csgp63pm9sfi72qhirl"; }; propagatedBuildInputs = [ self.ZopeInterface ]; meta = { homepage = http://twistedmatrix.com/; description = "Twisted, an event-driven networking engine written in Python"; license = stdenv.lib.licenses.mit; }; }; </programlisting> Most of Python packages that use <varname>buildPythonPackage</varname> are defined 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> and generated for each python interpreter separately into attribute sets <varname>python26Packages</varname>, <varname>python27Packages</varname>, <varname>python32Packages</varname>, <varname>python33Packages</varname>, <varname>python34Packages</varname> and <varname>pypyPackages</varname>. </para> <para> <function>buildPythonPackage</function> mainly does four things: <orderedlist> <listitem><para> In the <varname>configurePhase</varname>, it patches <literal>setup.py</literal> to always include setuptools before distutils for monkeypatching machinery to take place. </para></listitem> <listitem><para> In the <varname>buildPhase</varname>, it calls <literal>${python.interpreter} setup.py build ...</literal> </para></listitem> <listitem><para> In the <varname>installPhase</varname>, it calls <literal>${python.interpreter} setup.py install ...</literal> </para></listitem> <listitem><para> In the <varname>postFixup</varname> phase, <literal>wrapPythonPrograms</literal> bash function is called to wrap all programs in <filename>$out/bin/*</filename> directory to include <literal>$PYTHONPATH</literal> and <literal>$PATH</literal> environment variables. </para></listitem> </orderedlist> </para> <para>By default <varname>doCheck = true</varname> is set and tests are run with <literal>${python.interpreter} setup.py test</literal> command in <varname>checkPhase</varname>.</para> <para> As in Perl, dependencies on other Python packages can be specified in the <varname>buildInputs</varname> and <varname>propagatedBuildInputs</varname> attributes. If something is exclusively a build-time dependency, use <varname>buildInputs</varname>; if it’s (also) a runtime dependency, use <varname>propagatedBuildInputs</varname>. </para> <para> By default <varname>meta.platforms</varname> is set to the same value as the interpreter unless overriden otherwise. </para> <variablelist> <title> <varname>buildPythonPackage</varname> parameters (all parameters from <varname>mkDerivation</varname> function are still supported) </title> <varlistentry> <term><varname>namePrefix</varname></term> <listitem><para> Prepended text to <varname>${name}</varname> parameter. Defaults to <literal>"python3.3-"</literal> for Python 3.3, etc. Set it to <literal>""</literal> if you're packaging an application or a command line tool. </para></listitem> </varlistentry> <varlistentry> <term><varname>disabled</varname></term> <listitem><para> If <varname>true</varname>, package is not build for particular python interpreter version. Grep around <filename>pkgs/top-level/python-packages.nix</filename> for examples. </para></listitem> </varlistentry> <varlistentry> <term><varname>setupPyInstallFlags</varname></term> <listitem><para> List of flags passed to <command>setup.py install</command> command. </para></listitem> </varlistentry> <varlistentry> <term><varname>setupPyBuildFlags</varname></term> <listitem><para> List of flags passed to <command>setup.py build</command> command. </para></listitem> </varlistentry> <varlistentry> <term><varname>pythonPath</varname></term> <listitem><para> List of packages to be added into <literal>$PYTHONPATH</literal>. Packages in <varname>pythonPath</varname> are not propagated into user environment (contrary to <varname>propagatedBuildInputs</varname>). </para></listitem> </varlistentry> <varlistentry> <term><varname>preShellHook</varname></term> <listitem><para> Hook to execute commands before <varname>shellHook</varname>. </para></listitem> </varlistentry> <varlistentry> <term><varname>postShellHook</varname></term> <listitem><para> Hook to execute commands after <varname>shellHook</varname>. </para></listitem> </varlistentry> <varlistentry> <term><varname>distutilsExtraCfg</varname></term> <listitem><para> Extra lines passed to <varname>[easy_install]</varname> section of <filename>distutils.cfg</filename> (acts as global setup.cfg configuration). </para></listitem> </varlistentry> <varlistentry> <term><varname>makeWrapperArgs</varname></term> <listitem><para> A list of strings. Arguments to be passed to <varname>makeWrapper</varname>, which wraps generated binaries. By default, the arguments to <varname>makeWrapper</varname> set <varname>PATH</varname> and <varname>PYTHONPATH</varname> environment variables before calling the binary. Additional arguments here can allow a developer to set environment variables which will be available when the binary is run. For example, <varname>makeWrapperArgs = ["--set FOO BAR" "--set BAZ QUX"]</varname>. </para></listitem> </varlistentry> </variablelist> </section> <section xml:id="ssec-python-build-env"><title><function>python.buildEnv</function> function</title> <para> Create Python environments using low-level <function>pkgs.buildEnv</function> function. Example <filename>default.nix</filename>: <programlisting language="nix"> <![CDATA[with import <nixpkgs> {}; python.buildEnv.override { extraLibs = [ pkgs.pythonPackages.pyramid ]; ignoreCollisions = true; }]]> </programlisting> Running <command>nix-build</command> will create <filename>/nix/store/cf1xhjwzmdki7fasgr4kz6di72ykicl5-python-2.7.8-env</filename> with wrapped binaries in <filename>bin/</filename>. </para> <para> You can also use <varname>env</varname> attribute to create local environments with needed packages installed (somewhat comparable to <literal>virtualenv</literal>). For example, with the following <filename>shell.nix</filename>: <programlisting language="nix"> <![CDATA[with import <nixpkgs> {}; (python3.buildEnv.override { extraLibs = with python3Packages; [ numpy requests ]; }).env]]> </programlisting> Running <command>nix-shell</command> will drop you into a shell where <command>python</command> will have specified packages in its path. </para> <variablelist> <title> <function>python.buildEnv</function> arguments </title> <varlistentry> <term><varname>extraLibs</varname></term> <listitem><para> List of packages installed inside the environment. </para></listitem> </varlistentry> <varlistentry> <term><varname>postBuild</varname></term> <listitem><para> Shell command executed after the build of environment. </para></listitem> </varlistentry> <varlistentry> <term><varname>ignoreCollisions</varname></term> <listitem><para> Ignore file collisions inside the environment (default is <varname>false</varname>). </para></listitem> </varlistentry> </variablelist> </section> <section xml:id="ssec-python-tools"><title>Tools</title> <para>Packages inside nixpkgs are written by hand. However many tools exist in community to help save time. No tool is preferred at the moment. </para> <itemizedlist> <listitem><para> <link xlink:href="https://github.com/proger/python2nix">python2nix</link> by Vladimir Kirillov </para></listitem> <listitem><para> <link xlink:href="https://github.com/garbas/pypi2nix">pypi2nix</link> by Rok Garbas </para></listitem> <listitem><para> <link xlink:href="https://github.com/offlinehacker/pypi2nix">pypi2nix</link> by Jaka Hudoklin </para></listitem> </itemizedlist> </section> <section xml:id="ssec-python-development"><title>Development</title> <para> To develop Python packages <function>buildPythonPackage</function> has additional logic inside <varname>shellPhase</varname> to run <command>${python.interpreter} setup.py develop</command> for the package. </para> <warning><para><varname>shellPhase</varname> is executed only if <filename>setup.py</filename> exists.</para></warning> <para> Given a <filename>default.nix</filename>: <programlisting language="nix"> <![CDATA[with import <nixpkgs> {}; buildPythonPackage { name = "myproject"; buildInputs = with pkgs.pythonPackages; [ pyramid ]; src = ./.; }]]> </programlisting> Running <command>nix-shell</command> with no arguments should give you the environment in which the package would be build with <command>nix-build</command>. </para> <para> Shortcut to setup environments with C headers/libraries and python packages: <programlisting language="bash">$ nix-shell -p pythonPackages.pyramid zlib libjpeg git</programlisting> </para> <note><para> There is a boolean value <varname>lib.inNixShell</varname> set to <varname>true</varname> if nix-shell is invoked. </para></note> </section> <section xml:id="ssec-python-faq"><title>FAQ</title> <variablelist> <varlistentry> <term>How to solve circular dependencies?</term> <listitem><para> If you have packages <varname>A</varname> and <varname>B</varname> that depend on each other, when packaging <varname>B</varname> override package <varname>A</varname> not to depend on <varname>B</varname> as input (and also the other way around). </para></listitem> </varlistentry> <varlistentry> <term><varname>install_data / data_files</varname> problems resulting into <literal>error: could not create '/nix/store/6l1bvljpy8gazlsw2aw9skwwp4pmvyxw-python-2.7.8/etc': Permission denied</literal></term> <listitem><para> <link xlink:href="https://bitbucket.org/pypa/setuptools/issue/130/install_data-doesnt-respect-prefix"> Known bug in setuptools <varname>install_data</varname> does not respect --prefix</link>. Example of such package using the feature is <filename>pkgs/tools/X11/xpra/default.nix</filename>. As workaround install it as an extra <varname>preInstall</varname> step: <programlisting>${python.interpreter} setup.py install_data --install-dir=$out --root=$out sed -i '/ = data_files/d' setup.py</programlisting> </para></listitem> </varlistentry> <varlistentry> <term>Rationale of non-existent global site-packages</term> <listitem><para> There is no need to have global site-packages in Nix. Each package has isolated dependency tree and installing any python package will only populate <varname>$PATH</varname> inside user environment. See <xref linkend="ssec-python-build-env" /> to create self-contained interpreter with a set of packages. </para></listitem> </varlistentry> </variablelist> </section> <section xml:id="ssec-python-contrib"><title>Contributing guidelines</title> <para> Following rules are desired to be respected: </para> <itemizedlist> <listitem><para> Make sure package builds for all python interpreters. Use <varname>disabled</varname> argument to <function>buildPythonPackage</function> to set unsupported interpreters. </para></listitem> <listitem><para> If tests need to be disabled for a package, make sure you leave a comment about reasoning. </para></listitem> <listitem><para> Packages 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> are sorted quasi-alphabetically to avoid merge conflicts. </para></listitem> </itemizedlist> </section> </section> <section xml:id="sec-language-ruby"><title>Ruby</title> <para>There currently is support to bundle applications that are packaged as Ruby gems. The utility "bundix" allows you to write a <filename>Gemfile</filename>, let bundler create a <filename>Gemfile.lock</filename>, and then convert this into a nix expression that contains all Gem dependencies automatically.</para> <para>For example, to package sensu, we did:</para> <screen> <![CDATA[$ cd pkgs/servers/monitoring $ mkdir sensu $ cat > Gemfile source 'https://rubygems.org' gem 'sensu' $ bundler package --path /tmp/vendor/bundle $ $(nix-build '<nixpkgs>' -A bundix)/bin/bundix $ cat > default.nix { lib, bundlerEnv, ruby }: bundlerEnv { name = "sensu-0.17.1"; inherit ruby; gemfile = ./Gemfile; lockfile = ./Gemfile.lock; gemset = ./gemset.nix; meta = with lib; { description = "A monitoring framework that aims to be simple, malleable, and scalable."; homepage = http://sensuapp.org/; license = with licenses; mit; maintainers = with maintainers; [ theuni ]; platforms = platforms.unix; }; }]]> </screen> <para>Please check in the <filename>Gemfile</filename>, <filename>Gemfile.lock</filename> and the <filename>gemset.nix</filename> so future updates can be run easily. </para> </section> <section xml:id="sec-language-go"><title>Go</title> <para>The function <varname>buildGoPackage</varname> builds standard Go packages. </para> <example xml:id='ex-buildGoPackage'><title>buildGoPackage</title> <programlisting> net = buildGoPackage rec { name = "go.net-${rev}"; goPackagePath = "golang.org/x/net"; <co xml:id='ex-buildGoPackage-1' /> subPackages = [ "ipv4" "ipv6" ]; <co xml:id='ex-buildGoPackage-2' /> rev = "e0403b4e005"; src = fetchFromGitHub { inherit rev; owner = "golang"; repo = "net"; sha256 = "1g7cjzw4g4301a3yqpbk8n1d4s97sfby2aysl275x04g0zh8jxqp"; }; goPackageAliases = [ "code.google.com/p/go.net" ]; <co xml:id='ex-buildGoPackage-3' /> propagatedBuildInputs = [ goPackages.text ]; <co xml:id='ex-buildGoPackage-4' /> buildFlags = "--tags release"; <co xml:id='ex-buildGoPackage-5' /> disabled = isGo13;<co xml:id='ex-buildGoPackage-6' /> }; </programlisting> </example> <para><xref linkend='ex-buildGoPackage'/> is an example expression using buildGoPackage, the following arguments are of special significance to the function: <calloutlist> <callout arearefs='ex-buildGoPackage-1'> <para> <varname>goPackagePath</varname> specifies the package's canonical Go import path. </para> </callout> <callout arearefs='ex-buildGoPackage-2'> <para> <varname>subPackages</varname> limits the builder from building child packages that have not been listed. If <varname>subPackages</varname> is not specified, all child packages will be built. </para> <para> In this example only <literal>code.google.com/p/go.net/ipv4</literal> and <literal>code.google.com/p/go.net/ipv6</literal> will be built. </para> </callout> <callout arearefs='ex-buildGoPackage-3'> <para> <varname>goPackageAliases</varname> is a list of alternative import paths that are valid for this library. Packages that depend on this library will automatically rename import paths that match any of the aliases to <literal>goPackagePath</literal>. </para> <para> In this example imports will be renamed from <literal>code.google.com/p/go.net</literal> to <literal>golang.org/x/net</literal> in every package that depend on the <literal>go.net</literal> library. </para> </callout> <callout arearefs='ex-buildGoPackage-4'> <para> <varname>propagatedBuildInputs</varname> is where the dependencies of a Go library are listed. Only libraries should list <varname>propagatedBuildInputs</varname>. If a standalone program is being built instead, use <varname>buildInputs</varname>. If a library's tests require additional dependencies that are not propagated, they should be listed in <varname>buildInputs</varname>. </para> </callout> <callout arearefs='ex-buildGoPackage-5'> <para> <varname>buildFlags</varname> is a list of flags passed to the go build command. </para> </callout> <callout arearefs='ex-buildGoPackage-6'> <para> If <varname>disabled</varname> is <literal>true</literal>, nix will refuse to build this package. </para> <para> In this example the package will not be built for go 1.3. The <literal>isGo13</literal> is an utility function that returns <literal>true</literal> if go used to build the package has version 1.3.x. </para> </callout> </calloutlist> </para> <para> Reusable Go libraries may be found in the <varname>goPackages</varname> set. You can test build a Go package as follows: <screen> $ nix-build -A goPackages.net </screen> </para> <para> You may use Go packages installed into the active Nix profiles by adding the following to your ~/.bashrc: <screen> for p in $NIX_PROFILES; do GOPATH="$p/share/go:$GOPATH" done </screen> </para> <para>To extract dependency information from a Go package in automated way use <link xlink:href="https://github.com/cstrahan/go2nix">go2nix</link>.</para> </section> <section xml:id="sec-language-java"><title>Java</title> <para>Ant-based Java packages are typically built from source as follows: <programlisting> stdenv.mkDerivation { name = "..."; src = fetchurl { ... }; buildInputs = [ jdk ant ]; buildPhase = "ant"; } </programlisting> Note that <varname>jdk</varname> is an alias for the OpenJDK.</para> <para>JAR files that are intended to be used by other packages should be installed in <filename>$out/share/java</filename>. The OpenJDK has a stdenv setup hook that adds any JARs in the <filename>share/java</filename> directories of the build inputs to the <envar>CLASSPATH</envar> environment variable. For instance, if the package <literal>libfoo</literal> installs a JAR named <filename>foo.jar</filename> in its <filename>share/java</filename> directory, and another package declares the attribute <programlisting> buildInputs = [ jdk libfoo ]; </programlisting> then <envar>CLASSPATH</envar> will be set to <filename>/nix/store/...-libfoo/share/java/foo.jar</filename>.</para> <para>Private JARs should be installed in a location like <filename>$out/share/<replaceable>package-name</replaceable></filename>.</para> <para>If your Java package provides a program, you need to generate a wrapper script to run it using the OpenJRE. You can use <literal>makeWrapper</literal> for this: <programlisting> buildInputs = [ makeWrapper ]; installPhase = '' mkdir -p $out/bin makeWrapper ${jre}/bin/java $out/bin/foo \ --add-flags "-cp $out/share/java/foo.jar org.foo.Main" ''; </programlisting> Note the use of <literal>jre</literal>, which is the part of the OpenJDK package that contains the Java Runtime Environment. By using <literal>${jre}/bin/java</literal> instead of <literal>${jdk}/bin/java</literal>, you prevent your package from depending on the JDK at runtime.</para> <para>It is possible to use a different Java compiler than <command>javac</command> from the OpenJDK. For instance, to use the Eclipse Java Compiler: <programlisting> buildInputs = [ jre ant ecj ]; </programlisting> (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: <programlisting> buildInputs = [ gcj ant ]; </programlisting> Here, Ant will automatically use <command>gij</command> (the GNU Java Runtime) instead of the OpenJRE.</para> </section> <section xml:id="sec-language-lua"><title>Lua</title> <para> Lua packages are built by the <varname>buildLuaPackage</varname> function. This function is implemented in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/lua-modules/generic/default.nix"> <filename>pkgs/development/lua-modules/generic/default.nix</filename></link> and works similarly to <varname>buildPerlPackage</varname>. (See <xref linkend="sec-language-perl"/> for details.) </para> <para> Lua packages are defined in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/lua-packages.nix"><filename>pkgs/top-level/lua-packages.nix</filename></link>. Most of them are simple. For example: <programlisting> fileSystem = buildLuaPackage { name = "filesystem-1.6.2"; src = fetchurl { url = "https://github.com/keplerproject/luafilesystem/archive/v1_6_2.tar.gz"; sha256 = "1n8qdwa20ypbrny99vhkmx8q04zd2jjycdb5196xdhgvqzk10abz"; }; meta = { homepage = "https://github.com/keplerproject/luafilesystem"; hydraPlatforms = stdenv.lib.platforms.linux; maintainers = with maintainers; [ flosse ]; }; }; </programlisting> </para> <para> Though, more complicated package should be placed in a seperate file in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/lua-modules"><filename>pkgs/development/lua-modules</filename></link>. </para> <para> Lua packages accept additional parameter <varname>disabled</varname>, which defines the condition of disabling package from luaPackages. For example, if package has <varname>disabled</varname> assigned to <literal>lua.luaversion != "5.1"</literal>, it will not be included in any luaPackages except lua51Packages, making it only be built for lua 5.1. </para> </section> <section xml:id="sec-language-coq"><title>Coq</title> <para> Coq libraries should be installed in <literal>$(out)/lib/coq/${coq.coq-version}/user-contrib/</literal>. Such directories are automatically added to the <literal>$COQPATH</literal> environment variable by the hook defined in the Coq derivation. </para> <para> Some libraries require OCaml and sometimes also Camlp5. The exact versions that were used to build Coq are saved in the <literal>coq.ocaml</literal> and <literal>coq.camlp5</literal> attributes. </para> <para> Here is a simple package example. It is a pure Coq library, thus it only depends on Coq. Its <literal>makefile</literal> has been generated using <literal>coq_makefile</literal> so we only have to set the <literal>$COQLIB</literal> variable at install time. </para> <programlisting> {stdenv, fetchurl, coq}: stdenv.mkDerivation { src = fetchurl { url = http://coq.inria.fr/pylons/contribs/files/Karatsuba/v8.4/Karatsuba.tar.gz; sha256 = "0ymfpv4v49k4fm63nq6gcl1hbnnxrvjjp7yzc4973n49b853c5b1"; }; name = "coq-karatsuba"; buildInputs = [ coq ]; installFlags = "COQLIB=$(out)/lib/coq/${coq.coq-version}/"; } </programlisting> </section> <section xml:id="sec-language-qt"><title>Qt</title> <para>The information in this section applies to Qt 5.5 and later.</para> <para>Qt is an application development toolkit for C++. Although it is not a distinct programming language, there are special considerations for packaging Qt-based programs and libraries. A small set of tools and conventions has grown out of these considerations.</para> <section xml:id="ssec-qt-libraries"><title>Libraries</title> <para>Packages that provide libraries should be listed in <varname>qt5LibsFun</varname> so that the library is built with each Qt version. A set of packages is provided for each version of Qt; for example, <varname>qt5Libs</varname> always provides libraries built with the latest version, <varname>qt55Libs</varname> provides libraries built with Qt 5.5, and so on. To avoid version conflicts, no top-level attributes are created for these packages.</para> </section> <section xml:id="ssec-qt-programs"><title>Programs</title> <para>Application packages do not need to be built with every Qt version. To ensure consistency between the package's dependencies, call the package with <literal>qt5Libs.callPackage</literal> instead of the usual <literal>callPackage</literal>. An older version may be selected in case of incompatibility. For example, to build with Qt 5.5, call the package with <literal>qt55Libs.callPackage</literal>.</para> <para>Several environment variables must be set at runtime for Qt applications to function correctly, including:</para> <itemizedlist> <listitem><para><envar>QT_PLUGIN_PATH</envar></para></listitem> <listitem><para><envar>QML_IMPORT_PATH</envar></para></listitem> <listitem><para><envar>QML2_IMPORT_PATH</envar></para></listitem> <listitem><para><envar>XDG_DATA_DIRS</envar></para></listitem> </itemizedlist> <para>To ensure that these are set correctly, the program must be wrapped by invoking <literal>wrapQtProgram <replaceable>program</replaceable></literal> during installation (for example, during <literal>fixupPhase</literal>). <literal>wrapQtProgram</literal> accepts the same options as <literal>makeWrapper</literal>. </para> </section> <section xml:id="ssec-qt-kde"><title>KDE</title> <para>Many of the considerations above also apply to KDE packages, especially the need to set the correct environment variables at runtime. To ensure that this is done, invoke <literal>wrapKDEProgram <replaceable>program</replaceable></literal> during installation. <literal>wrapKDEProgram</literal> also generates a <literal>ksycoca</literal> database so that required data and services can be found. Like its Qt counterpart, <literal>wrapKDEProgram</literal> accepts the same options as <literal>makeWrapper</literal>.</para> </section> </section> <!-- <section><title>Haskell</title> <para>TODO</para> </section> <section><title>TeX / LaTeX</title> <para>* Special support for building TeX documents</para> </section> --> </chapter>