pyrox.dev
1# Bower {#sec-bower}
2
3[Bower](https://bower.io) is a package manager for web site front-end components. Bower packages (comprising of build artifacts 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.
4
5The end result of running Bower is a `bower_components` directory which can be included in the web app's build process.
6
7Bower 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`.
8
9## bower2nix usage {#ssec-bower2nix-usage}
10
11Suppose you have a `bower.json` with the following contents:
12
13### Example bower.json {#ex-bowerJson}
14
15```json
16 "name": "my-web-app",
17 "dependencies": {
18 "angular": "~1.5.0",
19 "bootstrap": "~3.3.6"
20 }
21```
22
23Running `bower2nix` will produce something like the following output:
24
25```nix
26{ fetchbower, buildEnv }:
27buildEnv { name = "bower-env"; ignoreCollisions = true; paths = [
28 (fetchbower "angular" "1.5.3" "~1.5.0" "1749xb0firxdra4rzadm4q9x90v6pzkbd7xmcyjk6qfza09ykk9y")
29 (fetchbower "bootstrap" "3.3.6" "~3.3.6" "1vvqlpbfcy0k5pncfjaiskj3y6scwifxygfqnw393sjfxiviwmbv")
30 (fetchbower "jquery" "2.2.2" "1.9.1 - 2" "10sp5h98sqwk90y4k6hbdviwqzvzwqf47r3r51pakch5ii2y7js1")
31];
32```
33
34Using the `bower2nix` command line arguments, the output can be redirected to a file. A name like `bower-packages.nix` would be fine.
35
36The 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.
37
38## buildBowerComponents function {#ssec-build-bower-components}
39
40The function is implemented in [pkgs/development/bower-modules/generic/default.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/bower-modules/generic/default.nix).
41
42### Example buildBowerComponents {#ex-buildBowerComponents}
43
44```nix
45bowerComponents = buildBowerComponents {
46 name = "my-web-app";
47 generated = ./bower-packages.nix; # note 1
48 src = myWebApp; # note 2
49};
50```
51
52In ["buildBowerComponents" example](#ex-buildBowerComponents) the following arguments are of special significance to the function:
53
541. `generated` specifies the file which was created by {command}`bower2nix`.
552. `src` is your project's sources. It needs to contain a {file}`bower.json` file.
56
57`buildBowerComponents` will run Bower to link together the output of `bower2nix`, resulting in a `bower_components` directory which can be used.
58
59Here is an example of a web frontend build process using `gulp`. You might use `grunt`, or anything else.
60
61### Example build script (gulpfile.js) {#ex-bowerGulpFile}
62
63```javascript
64var gulp = require('gulp');
65
66gulp.task('default', [], function () {
67 gulp.start('build');
68});
69
70gulp.task('build', [], function () {
71 console.log("Just a dummy gulp build");
72 gulp
73 .src(["./bower_components/**/*"])
74 .pipe(gulp.dest("./gulpdist/"));
75});
76```
77
78### Example Full example — default.nix {#ex-buildBowerComponentsDefaultNix}
79
80```nix
81{ myWebApp ? { outPath = ./.; name = "myWebApp"; }
82, pkgs ? import <nixpkgs> {}
83}:
84
85pkgs.stdenv.mkDerivation {
86 name = "my-web-app-frontend";
87 src = myWebApp;
88
89 buildInputs = [ pkgs.nodePackages.gulp ];
90
91 bowerComponents = pkgs.buildBowerComponents { # note 1
92 name = "my-web-app";
93 generated = ./bower-packages.nix;
94 src = myWebApp;
95 };
96
97 buildPhase = ''
98 cp --reflink=auto --no-preserve=mode -R $bowerComponents/bower_components . # note 2
99 export HOME=$PWD # note 3
100 ${pkgs.nodePackages.gulp}/bin/gulp build # note 4
101 '';
102
103 installPhase = "mv gulpdist $out";
104}
105```
106
107A few notes about [Full example — `default.nix`](#ex-buildBowerComponentsDefaultNix):
108
1091. The result of `buildBowerComponents` is an input to the frontend build.
1102. Whether to symlink or copy the {file}`bower_components` directory depends on the build tool in use.
111 In this case a copy is used to avoid {command}`gulp` silliness with permissions.
1123. {command}`gulp` requires `HOME` to refer to a writeable directory.
1134. The actual build command in this example is {command}`gulp`. Other tools could be used instead.
114
115## Troubleshooting {#ssec-bower2nix-troubleshooting}
116
117### ENOCACHE errors from buildBowerComponents {#enocache-errors-from-buildbowercomponents}
118
119This means that Bower was looking for a package version which doesn't exist in the generated `bower-packages.nix`.
120
121If `bower.json` has been updated, then run `bower2nix` again.
122
123It could also be a bug in `bower2nix` or `fetchbower`. If possible, try reformulating the version specification in `bower.json`.