<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-bower"> <title>Bower</title> <para> <link xlink:href="http://bower.io">Bower</link> is a package manager for web site front-end components. Bower packages (comprising of build artefacts and sometimes sources) are stored in <command>git</command> repositories, typically on Github. The package registry is run by the Bower team with package metadata coming from the <filename>bower.json</filename> file within each package. </para> <para> The end result of running Bower is a <filename>bower_components</filename> directory which can be included in the web app's build process. </para> <para> Bower can be run interactively, by installing <varname>nodePackages.bower</varname>. More interestingly, the Bower components can be declared in a Nix derivation, with the help of <varname>nodePackages.bower2nix</varname>. </para> <section xml:id="ssec-bower2nix-usage"> <title><command>bower2nix</command> usage</title> <para> Suppose you have a <filename>bower.json</filename> with the following contents: <example xml:id="ex-bowerJson"> <title><filename>bower.json</filename></title> <programlisting language="json"> <![CDATA[{ "name": "my-web-app", "dependencies": { "angular": "~1.5.0", "bootstrap": "~3.3.6" } }]]> </programlisting> </example> </para> <para> Running <command>bower2nix</command> will produce something like the following output: <programlisting language="nix"> <![CDATA[{ fetchbower, buildEnv }: buildEnv { name = "bower-env"; ignoreCollisions = true; paths = [ (fetchbower "angular" "1.5.3" "~1.5.0" "1749xb0firxdra4rzadm4q9x90v6pzkbd7xmcyjk6qfza09ykk9y") (fetchbower "bootstrap" "3.3.6" "~3.3.6" "1vvqlpbfcy0k5pncfjaiskj3y6scwifxygfqnw393sjfxiviwmbv") (fetchbower "jquery" "2.2.2" "1.9.1 - 2" "10sp5h98sqwk90y4k6hbdviwqzvzwqf47r3r51pakch5ii2y7js1") ]; }]]> </programlisting> </para> <para> Using the <command>bower2nix</command> command line arguments, the output can be redirected to a file. A name like <filename>bower-packages.nix</filename> would be fine. </para> <para> The resulting derivation is a union of all the downloaded Bower packages (and their dependencies). To use it, they still need to be linked together by Bower, which is where <varname>buildBowerComponents</varname> is useful. </para> </section> <section xml:id="ssec-build-bower-components"> <title><varname>buildBowerComponents</varname> function</title> <para> The function is implemented in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/bower-modules/generic/default.nix"> <filename>pkgs/development/bower-modules/generic/default.nix</filename></link>. Example usage: <example xml:id="ex-buildBowerComponents"> <title>buildBowerComponents</title> <programlisting language="nix"> bowerComponents = buildBowerComponents { name = "my-web-app"; generated = ./bower-packages.nix; <co xml:id="ex-buildBowerComponents-1" /> src = myWebApp; <co xml:id="ex-buildBowerComponents-2" /> }; </programlisting> </example> </para> <para> In <xref linkend="ex-buildBowerComponents" />, the following arguments are of special significance to the function: <calloutlist> <callout arearefs="ex-buildBowerComponents-1"> <para> <varname>generated</varname> specifies the file which was created by <command>bower2nix</command>. </para> </callout> <callout arearefs="ex-buildBowerComponents-2"> <para> <varname>src</varname> is your project's sources. It needs to contain a <filename>bower.json</filename> file. </para> </callout> </calloutlist> </para> <para> <varname>buildBowerComponents</varname> will run Bower to link together the output of <command>bower2nix</command>, resulting in a <filename>bower_components</filename> directory which can be used. </para> <para> Here is an example of a web frontend build process using <command>gulp</command>. You might use <command>grunt</command>, or anything else. </para> <example xml:id="ex-bowerGulpFile"> <title>Example build script (<filename>gulpfile.js</filename>)</title> <programlisting language="javascript"> <![CDATA[var gulp = require('gulp'); gulp.task('default', [], function () { gulp.start('build'); }); gulp.task('build', [], function () { console.log("Just a dummy gulp build"); gulp .src(["./bower_components/**/*"]) .pipe(gulp.dest("./gulpdist/")); });]]> </programlisting> </example> <example xml:id="ex-buildBowerComponentsDefaultNix"> <title>Full example — <filename>default.nix</filename></title> <programlisting language="nix"> { myWebApp ? { outPath = ./.; name = "myWebApp"; } , pkgs ? import <nixpkgs> {} }: pkgs.stdenv.mkDerivation { name = "my-web-app-frontend"; src = myWebApp; buildInputs = [ pkgs.nodePackages.gulp ]; bowerComponents = pkgs.buildBowerComponents { <co xml:id="ex-buildBowerComponentsDefault-1" /> name = "my-web-app"; generated = ./bower-packages.nix; src = myWebApp; }; buildPhase = '' cp --reflink=auto --no-preserve=mode -R $bowerComponents/bower_components . <co xml:id="ex-buildBowerComponentsDefault-2" /> export HOME=$PWD <co xml:id="ex-buildBowerComponentsDefault-3" /> ${pkgs.nodePackages.gulp}/bin/gulp build <co xml:id="ex-buildBowerComponentsDefault-4" /> ''; installPhase = "mv gulpdist $out"; } </programlisting> </example> <para> A few notes about <xref linkend="ex-buildBowerComponentsDefaultNix" />: <calloutlist> <callout arearefs="ex-buildBowerComponentsDefault-1"> <para> The result of <varname>buildBowerComponents</varname> is an input to the frontend build. </para> </callout> <callout arearefs="ex-buildBowerComponentsDefault-2"> <para> Whether to symlink or copy the <filename>bower_components</filename> directory depends on the build tool in use. In this case a copy is used to avoid <command>gulp</command> silliness with permissions. </para> </callout> <callout arearefs="ex-buildBowerComponentsDefault-3"> <para> <command>gulp</command> requires <varname>HOME</varname> to refer to a writeable directory. </para> </callout> <callout arearefs="ex-buildBowerComponentsDefault-4"> <para> The actual build command. Other tools could be used. </para> </callout> </calloutlist> </para> </section> <section xml:id="ssec-bower2nix-troubleshooting"> <title>Troubleshooting</title> <variablelist> <varlistentry> <term> <literal>ENOCACHE</literal> errors from <varname>buildBowerComponents</varname> </term> <listitem> <para> This means that Bower was looking for a package version which doesn't exist in the generated <filename>bower-packages.nix</filename>. </para> <para> If <filename>bower.json</filename> has been updated, then run <command>bower2nix</command> again. </para> <para> It could also be a bug in <command>bower2nix</command> or <command>fetchbower</command>. If possible, try reformulating the version specification in <filename>bower.json</filename>. </para> </listitem> </varlistentry> </variablelist> </section> </section>