mirror of
https://github.com/NixOS/nixpkgs.git
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505508a813
Improve beam docs: * correct spelling * update per pandoc changes * capitalize titles * capitalize BEAM throughout and use "the BEAM" when referring to the virtual machine. * tweak grammar and phrasing * reformat build-tools-rebar3 section * add more links * re-wrap <para>s Also update <programlisting>s * normalize whitespace * don't double quote homepage * use $ in all shell snippets
475 lines
17 KiB
XML
475 lines
17 KiB
XML
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xml:id="sec-beam">
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<title>BEAM Languages (Erlang, Elixir & LFE)</title>
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<section xml:id="beam-introduction">
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<title>Introduction</title>
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<para>
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In this document and related Nix expressions, we use the term,
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<emphasis>BEAM</emphasis>, to describe the environment. BEAM is the name
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of the Erlang Virtual Machine and, as far as we're concerned, from a
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packaging perspective, all languages that run on the BEAM are
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interchangeable. That which varies, like the build system, is transparent
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to users of any given BEAM package, so we make no distinction.
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</para>
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</section>
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<section xml:id="beam-structure">
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<title>Structure</title>
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<para>
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All BEAM-related expressions are available via the top-level
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<literal>beam</literal> attribute, which includes:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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<literal>interpreters</literal>: a set of compilers running on the
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BEAM, including multiple Erlang/OTP versions
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(<literal>beam.interpreters.erlangR19</literal>, etc), Elixir
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(<literal>beam.interpreters.elixir</literal>) and LFE
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(<literal>beam.interpreters.lfe</literal>).
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>packages</literal>: a set of package sets, each compiled with
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a specific Erlang/OTP version, e.g.
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<literal>beam.packages.erlangR19</literal>.
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</para>
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</listitem>
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</itemizedlist>
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<para>
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The default Erlang compiler, defined by
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<literal>beam.interpreters.erlang</literal>, is aliased as
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<literal>erlang</literal>. The default BEAM package set is defined by
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<literal>beam.packages.erlang</literal> and aliased at the top level as
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<literal>beamPackages</literal>.
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</para>
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<para>
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To create a package set built with a custom Erlang version, use the
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lambda, <literal>beam.packagesWith</literal>, which accepts an Erlang/OTP
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derivation and produces a package set similar to
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<literal>beam.packages.erlang</literal>.
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</para>
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<para>
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Many Erlang/OTP distributions available in
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<literal>beam.interpreters</literal> have versions with ODBC and/or Java
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enabled. For example, there's
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<literal>beam.interpreters.erlangR19_odbc_javac</literal>, which
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corresponds to <literal>beam.interpreters.erlangR19</literal>.
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</para>
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<para xml:id="erlang-call-package">
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We also provide the lambda,
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<literal>beam.packages.erlang.callPackage</literal>, which simplifies
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writing BEAM package definitions by injecting all packages from
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<literal>beam.packages.erlang</literal> into the top-level context.
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</para>
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</section>
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<section xml:id="build-tools">
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<title>Build Tools</title>
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<section xml:id="build-tools-rebar3">
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<title>Rebar3</title>
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<para>
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By default, Rebar3 wants to manage its own dependencies. This is perfectly
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acceptable in the normal, non-Nix setup, but in the Nix world, it is not.
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To rectify this, we provide two versions of Rebar3:
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<itemizedlist>
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<listitem>
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<para>
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<literal>rebar3</literal>: patched to remove the ability to download
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anything. When not running it via <literal>nix-shell</literal> or
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<literal>nix-build</literal>, it's probably not going to work as
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desired.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>rebar3-open</literal>: the normal, unmodified Rebar3. It
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should work exactly as would any other version of Rebar3. Any Erlang
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package should rely on <literal>rebar3</literal> instead. See <xref
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linkend="rebar3-packages"/>.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</section>
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<section xml:id="build-tools-other">
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<title>Mix & Erlang.mk</title>
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<para>
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Both Mix and Erlang.mk work exactly as expected. There is a bootstrap
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process that needs to be run for both, however, which is supported by the
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<literal>buildMix</literal> and <literal>buildErlangMk</literal>
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derivations, respectively.
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</para>
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</section>
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</section>
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<section xml:id="how-to-install-beam-packages">
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<title>How to Install BEAM Packages</title>
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<para>
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BEAM packages are not registered at the top level, simply because they are
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not relevant to the vast majority of Nix users. They are installable using
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the <literal>beam.packages.erlang</literal> attribute set (aliased as
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<literal>beamPackages</literal>), which points to packages built by the
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default Erlang/OTP version in Nixpkgs, as defined by
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<literal>beam.interpreters.erlang</literal>.
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To list the available packages in
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<literal>beamPackages</literal>, use the following command:
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</para>
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<programlisting>
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$ nix-env -f "<nixpkgs>" -qaP -A beamPackages
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beamPackages.esqlite esqlite-0.2.1
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beamPackages.goldrush goldrush-0.1.7
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beamPackages.ibrowse ibrowse-4.2.2
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beamPackages.jiffy jiffy-0.14.5
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beamPackages.lager lager-3.0.2
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beamPackages.meck meck-0.8.3
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beamPackages.rebar3-pc pc-1.1.0
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</programlisting>
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<para>
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To install any of those packages into your profile, refer to them by their
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attribute path (first column):
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</para>
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<programlisting>
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$ nix-env -f "<nixpkgs>" -iA beamPackages.ibrowse
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</programlisting>
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<para>
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The attribute path of any BEAM package corresponds to the name of that
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particular package in <link xlink:href="https://hex.pm">Hex</link> or its
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OTP Application/Release name.
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</para>
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</section>
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<section xml:id="packaging-beam-applications">
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<title>Packaging BEAM Applications</title>
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<section xml:id="packaging-erlang-applications">
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<title>Erlang Applications</title>
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<section xml:id="rebar3-packages">
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<title>Rebar3 Packages</title>
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<para>
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The Nix function, <literal>buildRebar3</literal>, defined in
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<literal>beam.packages.erlang.buildRebar3</literal> and aliased at the
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top level, can be used to build a derivation that understands how to
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build a Rebar3 project. For example, we can build <link
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xlink:href="https://github.com/erlang-nix/hex2nix">hex2nix</link> as
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follows:
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</para>
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<programlisting>
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{ stdenv, fetchFromGitHub, buildRebar3, ibrowse, jsx, erlware_commons }:
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buildRebar3 rec {
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name = "hex2nix";
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version = "0.0.1";
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src = fetchFromGitHub {
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owner = "ericbmerritt";
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repo = "hex2nix";
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rev = "${version}";
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sha256 = "1w7xjidz1l5yjmhlplfx7kphmnpvqm67w99hd2m7kdixwdxq0zqg";
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};
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beamDeps = [ ibrowse jsx erlware_commons ];
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}
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</programlisting>
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<para>
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Such derivations are callable with
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<literal>beam.packages.erlang.callPackage</literal> (see <xref
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linkend="erlang-call-package"/>). To call this package using the normal
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<literal>callPackage</literal>, refer to dependency packages via
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<literal>beamPackages</literal>, e.g.
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<literal>beamPackages.ibrowse</literal>.
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</para>
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<para>
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Notably, <literal>buildRebar3</literal> includes
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<literal>beamDeps</literal>, while
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<literal>stdenv.mkDerivation</literal> does not. BEAM dependencies added
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there will be correctly handled by the system.
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</para>
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<para>
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If a package needs to compile native code via Rebar3's port compilation
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mechanism, add <literal>compilePort = true;</literal> to the derivation.
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</para>
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</section>
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<section xml:id="erlang-mk-packages">
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<title>Erlang.mk Packages</title>
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<para>
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Erlang.mk functions similarly to Rebar3, except we use
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<literal>buildErlangMk</literal> instead of
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<literal>buildRebar3</literal>.
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</para>
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<programlisting>
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{ buildErlangMk, fetchHex, cowlib, ranch }:
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buildErlangMk {
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name = "cowboy";
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version = "1.0.4";
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src = fetchHex {
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pkg = "cowboy";
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version = "1.0.4";
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sha256 = "6a0edee96885fae3a8dd0ac1f333538a42e807db638a9453064ccfdaa6b9fdac";
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};
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beamDeps = [ cowlib ranch ];
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meta = {
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description = ''
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Small, fast, modular HTTP server written in Erlang
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'';
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license = stdenv.lib.licenses.isc;
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homepage = https://github.com/ninenines/cowboy;
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};
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}
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</programlisting>
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</section>
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<section xml:id="mix-packages">
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<title>Mix Packages</title>
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<para>
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Mix functions similarly to Rebar3, except we use
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<literal>buildMix</literal> instead of <literal>buildRebar3</literal>.
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</para>
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<programlisting>
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{ buildMix, fetchHex, plug, absinthe }:
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buildMix {
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name = "absinthe_plug";
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version = "1.0.0";
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src = fetchHex {
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pkg = "absinthe_plug";
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version = "1.0.0";
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sha256 = "08459823fe1fd4f0325a8bf0c937a4520583a5a26d73b193040ab30a1dfc0b33";
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};
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beamDeps = [ plug absinthe ];
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meta = {
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description = ''
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A plug for Absinthe, an experimental GraphQL toolkit
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'';
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license = stdenv.lib.licenses.bsd3;
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homepage = https://github.com/CargoSense/absinthe_plug;
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};
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}
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</programlisting>
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<para>
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Alternatively, we can use <literal>buildHex</literal> as a shortcut:
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</para>
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<programlisting>
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{ buildHex, buildMix, plug, absinthe }:
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buildHex {
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name = "absinthe_plug";
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version = "1.0.0";
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sha256 = "08459823fe1fd4f0325a8bf0c937a4520583a5a26d73b193040ab30a1dfc0b33";
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builder = buildMix;
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beamDeps = [ plug absinthe ];
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meta = {
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description = ''
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A plug for Absinthe, an experimental GraphQL toolkit
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'';
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license = stdenv.lib.licenses.bsd3;
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homepage = https://github.com/CargoSense/absinthe_plug;
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};
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}
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</programlisting>
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</section>
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</section>
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</section>
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<section xml:id="how-to-develop">
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<title>How to Develop</title>
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<section xml:id="accessing-an-environment">
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<title>Accessing an Environment</title>
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<para>
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Often, we simply want to access a valid environment that contains a
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specific package and its dependencies. We can accomplish that with the
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<literal>env</literal> attribute of a derivation. For example, let's say
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we want to access an Erlang REPL with <literal>ibrowse</literal> loaded
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up. We could do the following:
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</para>
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<programlisting>
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$ nix-shell -A beamPackages.ibrowse.env --run "erl"
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Erlang/OTP 18 [erts-7.0] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]
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Eshell V7.0 (abort with ^G)
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1> m(ibrowse).
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Module: ibrowse
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MD5: 3b3e0137d0cbb28070146978a3392945
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Compiled: January 10 2016, 23:34
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Object file: /nix/store/g1rlf65rdgjs4abbyj4grp37ry7ywivj-ibrowse-4.2.2/lib/erlang/lib/ibrowse-4.2.2/ebin/ibrowse.beam
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Compiler options: [{outdir,"/tmp/nix-build-ibrowse-4.2.2.drv-0/hex-source-ibrowse-4.2.2/_build/default/lib/ibrowse/ebin"},
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debug_info,debug_info,nowarn_shadow_vars,
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warn_unused_import,warn_unused_vars,warnings_as_errors,
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{i,"/tmp/nix-build-ibrowse-4.2.2.drv-0/hex-source-ibrowse-4.2.2/_build/default/lib/ibrowse/include"}]
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Exports:
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add_config/1 send_req_direct/7
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all_trace_off/0 set_dest/3
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code_change/3 set_max_attempts/3
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get_config_value/1 set_max_pipeline_size/3
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get_config_value/2 set_max_sessions/3
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get_metrics/0 show_dest_status/0
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get_metrics/2 show_dest_status/1
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handle_call/3 show_dest_status/2
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handle_cast/2 spawn_link_worker_process/1
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handle_info/2 spawn_link_worker_process/2
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init/1 spawn_worker_process/1
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module_info/0 spawn_worker_process/2
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module_info/1 start/0
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rescan_config/0 start_link/0
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rescan_config/1 stop/0
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send_req/3 stop_worker_process/1
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send_req/4 stream_close/1
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send_req/5 stream_next/1
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send_req/6 terminate/2
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send_req_direct/4 trace_off/0
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send_req_direct/5 trace_off/2
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send_req_direct/6 trace_on/0
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trace_on/2
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ok
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2>
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</programlisting>
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<para>
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Notice the <literal>-A beamPackages.ibrowse.env</literal>. That is the key
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to this functionality.
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</para>
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</section>
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<section xml:id="creating-a-shell">
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<title>Creating a Shell</title>
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<para>
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Getting access to an environment often isn't enough to do real
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development. Usually, we need to create a <literal>shell.nix</literal>
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file and do our development inside of the environment specified therein.
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This file looks a lot like the packaging described above, except that
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<literal>src</literal> points to the project root and we call the package
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directly.
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</para>
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<programlisting>
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{ pkgs ? import "<nixpkgs"> {} }:
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with pkgs;
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let
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f = { buildRebar3, ibrowse, jsx, erlware_commons }:
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buildRebar3 {
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name = "hex2nix";
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version = "0.1.0";
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src = ./.;
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beamDeps = [ ibrowse jsx erlware_commons ];
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};
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drv = beamPackages.callPackage f {};
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in
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drv
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</programlisting>
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<section xml:id="building-in-a-shell">
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<title>Building in a Shell (for Mix Projects)</title>
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<para>
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We can leverage the support of the derivation, irrespective of the build
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derivation, by calling the commands themselves.
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</para>
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<programlisting>
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# =============================================================================
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# Variables
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# =============================================================================
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NIX_TEMPLATES := "$(CURDIR)/nix-templates"
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TARGET := "$(PREFIX)"
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PROJECT_NAME := thorndyke
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NIXPKGS=../nixpkgs
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NIX_PATH=nixpkgs=$(NIXPKGS)
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NIX_SHELL=nix-shell -I "$(NIX_PATH)" --pure
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# =============================================================================
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# Rules
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# =============================================================================
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.PHONY= all test clean repl shell build test analyze configure install \
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test-nix-install publish plt analyze
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all: build
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guard-%:
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@ if [ "${${*}}" == "" ]; then \
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echo "Environment variable $* not set"; \
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exit 1; \
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fi
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clean:
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rm -rf _build
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rm -rf .cache
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repl:
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$(NIX_SHELL) --run "iex -pa './_build/prod/lib/*/ebin'"
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shell:
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$(NIX_SHELL)
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configure:
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$(NIX_SHELL) --command 'eval "$$configurePhase"'
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build: configure
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$(NIX_SHELL) --command 'eval "$$buildPhase"'
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install:
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$(NIX_SHELL) --command 'eval "$$installPhase"'
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test:
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$(NIX_SHELL) --command 'mix test --no-start --no-deps-check'
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plt:
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$(NIX_SHELL) --run "mix dialyzer.plt --no-deps-check"
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analyze: build plt
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$(NIX_SHELL) --run "mix dialyzer --no-compile"
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</programlisting>
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<para>
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Using a <literal>shell.nix</literal> as described (see <xref
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linkend="creating-a-shell"/>) should just work. Aside from
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<literal>test</literal>, <literal>plt</literal>, and
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<literal>analyze</literal>, the Make targets work just fine for all of the
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build derivations.
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</para>
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</section>
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</section>
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</section>
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<section xml:id="generating-packages-from-hex-with-hex2nix">
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<title>Generating Packages from Hex with <literal>hex2nix</literal></title>
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<para>
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Updating the <link xlink:href="https://hex.pm">Hex</link> package set
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requires <link
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xlink:href="https://github.com/erlang-nix/hex2nix">hex2nix</link>. Given the
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path to the Erlang modules (usually
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<literal>pkgs/development/erlang-modules</literal>), it will dump a file
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called <literal>hex-packages.nix</literal>, containing all the packages that
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use a recognized build system in <link
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xlink:href="https://hex.pm">Hex</link>. It can't be determined, however,
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whether every package is buildable.
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</para>
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<para>
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To make life easier for our users, try to build every <link
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xlink:href="https://hex.pm">Hex</link> package and remove those that fail.
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To do that, simply run the following command in the root of your
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<literal>nixpkgs</literal> repository:
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</para>
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<programlisting>
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$ nix-build -A beamPackages
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</programlisting>
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<para>
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That will attempt to build every package in
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|
<literal>beamPackages</literal>. Then manually remove those that fail.
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|
Hopefully, someone will improve <link
|
|
xlink:href="https://github.com/erlang-nix/hex2nix">hex2nix</link> in the
|
|
future to automate the process.
|
|
</para>
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|
</section>
|
|
</section>
|