GruntJs Access to package.json

25 October 2012

Have you used GruntJs to build your JavaScript project yet? It's a great tool. Often as a part of the build configuration, you'll want to access your package.json with grunt. Grunt has some built-in support for this. Some bits can be a little tricky, and some plugins have limited support. Here are some ways around all that.

Grunt JSON Directive

Grunt supports a number of directives out of the box. These are callable from within you grunt.js file. The gruntfile template uses one of these directives like so:

grunt.initConfig({
  pkg: '<json:package.json>',
  /* ... */
});

This is making the contents of your package.json file available to your grunt config. And this is what we wanted! So, if I want to put the version of my app into some grunt task config, I can use it like so:

someTask: {
  options: 'doStuff <%= pkg.version %>'
}

This would already be enough -- it it worked all the time! Turns out it doesn't .

grunt.template

This syntax ("<%= someVar %>") is referred to as a grunt.template. It is based on underscore's template function.

Grunt Plugin Support

It turns out that all plugins are not created equal. Some plugins do not support this syntax at all. I wrestled with mainly two plugins

grunt-exec - for executing scripts/commands in the shell
grunt-jade - for compiling jade templates

As far as I can tell, neither plugin supports grunt.template. Lameo. In the case of grunt-jade, I actually switched plugins to grunt-contrib-jade, which states explicit support for grunt.template in the docs. Other than the docs or trying it out, I otherwise don't know how to determine support.

Access package.json Directly

Where I couldn't find a plugin that explicitly supported grunt.template, I needed another solution. Guided by the power of Google, I ran across a good Stack Overflow post on getting package.json values into the grunt.js file.

The post illuminated my dim mind: Grunt runs in node. Do what you would do in node.

Thusly, I just require the package.json file, and it is available. Voila. Who needs a stinkin template directive? And it looks like:

var pkgJson = require('./package.json');

/* use as desired */
var version = pkgJson.version;

My one departure from the Stack Overflow suggestion was to use a different variable name on the require statement ('package' -> 'pkgJson'). 'package' is a keyword that doesn't pass linting.

Grunt access package.json

As it turns out, Grunt has not problem accessing package.json. Grunt was already a venerable build tool option. Now, it running Javascript, speaking to your Javascript project descriptor (package.json) is pure genius. And genius that is easily accomplished? -- noteworthy indeed.