How do you specify configuration dependencies for your app? Say you have app configuration that depends on other bits of app configuration (for example, some config lives at an http endpoint, but you need to read the endpoint URL from some other config before you can hit it).

config-dependency-dreamcode.js

/**
 * Add support for config dependencies. This allows you to specify 
 * configuration that other configuration depends upon.
 */
test('Dependencies v4.callback', function (t) {
  qconf.clear();
  var subject = {hello: 'world'},
    sentence = function (subject, cb) {
      cb(null, 'goobye, cruel ' + subject);
    };

  // Callback = Return undefined.  
  qconf([{
      name: 'subject',
      source: subject
    },
    {
      name: 'sentence',
      source: sentence,
      dependencies: ['subject']
    }
  ], 
  function (err, conf) {
    t.error('Should not cause error.');
    t.equal(conf.get(sentence), 'goodbye, cruel world');
    t.end();
  });

});


test('Dependencies v4.promise', function (t) {
  qconf.clear();
  var subject = {hello: 'world'},
    sentence = function (subject, cb) {
      cb(null, 'goobye, cruel ' + subject);
    };

  // No callback = return promise.
  loadConfig = qconf([{
      name: 'subject',
      source: subject
    },
    {
      name: 'sentence',
      source: sentence,
      dependencies: ['subject']
    }
  ]).then(function (conf) {
    t.equal(conf.get(sentence), 'goodbye, cruel world');
    t.end();  
  }, function (err) {
    t.error(err, 'Should not cause error.')
  });
});