conditions.js

/*
Copyright 2014 Yahoo! Inc. All rights reserved.
Licensed under the BSD License.
https://github.com/yahoo/es-loader-extensions/blob/master/LICENSE.md
*/
/*jslint esnext: true*/
/*global Promise*/
export default function (loader, options) {
    var loaderNormalize = loader.normalize.bind(loader),
        triggers        = options.triggers || {};

    function testCondition(name) {
        var trigger = triggers[name];
        
        if (!trigger) {
            return name;
        }

        if (typeof trigger.test !== 'function') {
            throw new TypeError('Triggers must include a test function');
        }
        // Trigger tests may return true/false or a promise for a boolean
        // value. Promise failures are interpreted as test failures,
        // same as returning false.
        // Also, testCondition being run inside a Promise init function
        // means thrown errors are turned into test failures
        return new Promise(function (resolve, reject) {
            // tests being run inside a Promise initialization function
            // means thrown errors are turned into test failures
            try {
                resolve(trigger.test());
            } catch (err) {
                reject(err);
            }
        }).then(function (result) {
            return result ? trigger.replaceWith : name;
        }, function () {
            return name;
        });
    }

    loader.normalize = function (name) {
        return Promise.resolve(loaderNormalize(name)).then(testCondition);
    };
}