Bower
Bower is a package manager for web
site front-end components. Bower packages (comprising of build artefacts and
sometimes sources) are stored in git repositories,
typically on Github. The package registry is run by the Bower team with
package metadata coming from the bower.json file within
each package.
The end result of running Bower is a bower_components
directory which can be included in the web app's build process.
Bower can be run interactively, by installing
nodePackages.bower. More interestingly, the Bower
components can be declared in a Nix derivation, with the help of
nodePackages.bower2nix.
<command>bower2nix</command> usage
Suppose you have a bower.json with the following
contents:
<filename>bower.json</filename>
Running bower2nix will produce something like the
following output:
Using the bower2nix command line arguments, the output
can be redirected to a file. A name like
bower-packages.nix would be fine.
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 buildBowerComponents is useful.
<varname>buildBowerComponents</varname> function
The function is implemented in
pkgs/development/bower-modules/generic/default.nix.
Example usage:
buildBowerComponents
bowerComponents = buildBowerComponents {
name = "my-web-app";
generated = ./bower-packages.nix;
src = myWebApp;
};
In , the following arguments are
of special significance to the function:
generated specifies the file which was created by
bower2nix.
src is your project's sources. It needs to contain a
bower.json file.
buildBowerComponents will run Bower to link together the
output of bower2nix, resulting in a
bower_components directory which can be used.
Here is an example of a web frontend build process using
gulp. You might use grunt, or anything
else.
Example build script (<filename>gulpfile.js</filename>)Full example — <filename>default.nix</filename>
{ myWebApp ? { outPath = ./.; name = "myWebApp"; }
, pkgs ? import <nixpkgs> {}
}:
pkgs.stdenv.mkDerivation {
name = "my-web-app-frontend";
src = myWebApp;
buildInputs = [ pkgs.nodePackages.gulp ];
bowerComponents = pkgs.buildBowerComponents {
name = "my-web-app";
generated = ./bower-packages.nix;
src = myWebApp;
};
buildPhase = ''
cp --reflink=auto --no-preserve=mode -R $bowerComponents/bower_components .
export HOME=$PWD
${pkgs.nodePackages.gulp}/bin/gulp build
'';
installPhase = "mv gulpdist $out";
}
A few notes about :
The result of buildBowerComponents is an input to the
frontend build.
Whether to symlink or copy the bower_components
directory depends on the build tool in use. In this case a copy is used
to avoid gulp silliness with permissions.
gulp requires HOME to refer to a
writeable directory.
The actual build command. Other tools could be used.
TroubleshootingENOCACHE errors from
buildBowerComponents
This means that Bower was looking for a package version which doesn't
exist in the generated bower-packages.nix.
If bower.json has been updated, then run
bower2nix again.
It could also be a bug in bower2nix or
fetchbower. If possible, try reformulating the version
specification in bower.json.