promise.js

  showDashboardLink: Ember.computed(
    function() {
      if (this.get('session.isAuthenticated')) {
        return this.get('store').findAll('datasource').then((datasources) => {
          this.get('store').filter('datasource', {}, function(datasource) {
            return datasource.get('id') != null;
          }).then((datasources) => {
            if (datasources.get('length') != 0) {
              return true
            } else {
              return false
            }
          });
        });
      } else {
        return false
      }
    }
  ),

(datasources) => {
              this.set('showDashboardLink', true);
            }.bind(this)

unnecesary bind