dependency-check/tasks/dependency-check.js

checks which modules you have used in your code and then makes sure they are listed as dependencies in your package.json

module.exports = function (grunt) {
  var check = require('../')

  grunt.registerMultiTask('dependency-check', 'Matches used modules to listed dependencies', function () {
    var done = this.async()

    var options = this.options({
      missing: true,
      unused: true,
      excludeMissingDev: false,
      package: '.'
    })

    check({path: options.package, entries: this.filesSrc}, function(err, data) {
      if (err) {
        return grunt.fail.fatal(err)
      }

      var pkg = data.package
      var deps = data.used
      var results

      if (options.unused) {
        results = check.extra(pkg, deps, {excludeDev: options.excludeMissingDev})
        if (results.length !== 0) {
          grunt.log.error('Modules in package.json not used in code: ' + grunt.log.wordlist(results, {color: 'red'}))
        }
      }

      if (options.missing) {
        results = check.missing(pkg, deps)
        if (results.length !== 0) {
          grunt.fail.fatal('Dependencies not listed in package.json: ' + grunt.log.wordlist(results, {color: 'red'}))
        }
      }

      done()
    })
  })
}