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Diffstat (limited to 'doc')
-rw-r--r-- | doc/coding-conventions.xml | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/doc/coding-conventions.xml b/doc/coding-conventions.xml index 282fad66280cb..e55f86ae3d31f 100644 --- a/doc/coding-conventions.xml +++ b/doc/coding-conventions.xml @@ -207,6 +207,79 @@ args.stdenv.mkDerivation (args // { </section> +<section><title>Package naming</title> + +<para>In Nixpkgs, there are generally three different names associated with a package: + +<itemizedlist> + + <listitem><para>The <varname>name</varname> attribute of the + derivation (excluding the version part). This is what most users + see, in particular when using + <command>nix-env</command>.</para></listitem> + + <listitem><para>The variable name used for the instantiated package + in <filename>all-packages.nix</filename>, and when passing it as a + dependency to other functions. This is what Nix expression authors + see. It can also be used when installing using <command>nix-env + -iA</command>.</para></listitem> + + <listitem><para>The filename for (the directory containing) the Nix + expression.</para></listitem> + +</itemizedlist> + +Most of the time, these are the same. For instance, the package +<literal>e2fsprogs</literal> has a <varname>name</varname> attribute +<literal>"e2fsprogs-<replaceable>version</replaceable>"</literal>, is +bound to the variable name <varname>e2fsprogs</varname> in +<filename>all-packages.nix</filename>, and the Nix expression is in +<filename>pkgs/os-specific/linux/e2fsprogs/default.nix</filename>. +However, identifiers in the Nix language don’t allow certain +characters (e.g. dashes), so sometimes a different variable name +should be used. For instance, the +<literal>module-init-tools</literal> package is bound to the +<literal>module_init_tools</literal> variable in +<filename>all-packages.nix</filename>.</para> + +<para>There are a few naming guidelines: + +<itemizedlist> + + <listitem><para>Generally, try to stick to the upstream package + name.</para></listitem> + + <listitem><para>Don’t use uppercase letters in the + <literal>name</literal> attribute — e.g., + <literal>"mplayer-1.0rc2"</literal> instead of + <literal>"MPlayer-1.0rc2"</literal>.</para></listitem> + + <listitem><para>The version part of the <literal>name</literal> + attribute <emphasis>must</emphasis> start with a digit (following a + dash) — e.g., <literal>"hello-0.3-pre-r3910"</literal> instead of + <literal>"hello-svn-r3910"</literal>, as the latter would be seen as + a package named <literal>hello-svn</literal> by + <command>nix-env</command>.</para></listitem> + + <listitem><para>Dashes in the package name should be changed to + underscores in variable names, rather than to camel case — e.g., + <varname>module_init_tools</varname> instead of + <varname>moduleInitTools</varname>.</para></listitem> + + <listitem><para>If there are multiple versions of a package, this + should be reflected in the variable names in + <filename>all-packages.nix</filename>, + e.g. <varname>hello_0_3</varname> and <varname>hello_0_4</varname>. + If there is an obvious “default” version, make an attribute like + <literal>hello = hello_0_4;</literal>.</para></listitem> + +</itemizedlist> + +</para> + +</section> + + <section xml:id="sec-organisation"><title>File naming and organisation</title> <para>Names of files and directories should be in lowercase, with @@ -215,6 +288,8 @@ dashes between words — not in camel case. For instance, it should be <filename>allPackages.nix</filename> or <filename>AllPackages.nix</filename>.</para> +<section><title>Hierachy</title> + <para>Each package should be stored in its own directory somewhere in the <filename>pkgs/</filename> tree, i.e. in <filename>pkgs/<replaceable>category</replaceable>/<replaceable>subcategory</replaceable>/<replaceable>...</replaceable>/<replaceable>pkgname</replaceable></filename>. @@ -492,4 +567,39 @@ splitting up an existing category.</para> </section> +<section><title>Versioning</title> + +<para>Because every version of a package in Nixpkgs creates a +potential maintenance burden, old versions of a package should not be +kept unless there is a good reason to do so. For instance, Nixpkgs +contains several versions of GCC because other packages don’t build +with the latest version of GCC. Other examples are having both the +latest stable and latest pre-release version of a package, or to keep +several major releases of an application that differ significantly in +functionality.</para> + +<para>If there is only one version of a package, its Nix expression +should be named <filename>e2fsprogs/default.nix</filename>. If there +are multiple versions, this should be reflected in the filename, +e.g. <filename>e2fsprogs/1.41.8.nix</filename> and +<filename>e2fsprogs/1.41.9.nix</filename>. The version in the +filename should leave out unnecessary detail. For instance, if we +keep the latest Firefox 2.0.x and 3.5.x versions in Nixpkgs, they +should be named <filename>firefox/2.0.nix</filename> and +<filename>firefox/3.5.nix</filename>, respectively (which, at a given +point, might contain versions <literal>2.0.0.20</literal> and +<literal>3.5.4</literal>). If a version requires many auxiliary +files, you can use a subdirectory for each version, +e.g. <filename>firefox/2.0/default.nix</filename> and +<filename>firefox/3.5/default.nix</filename>.</para> + +<para>All versions of a package <emphasis>must</emphasis> be included +in <filename>all-packages.nix</filename> to make sure that they +evaluate correctly.</para> + +</section> + +</section> + + </chapter> |