istanbul/lib/util/yui-load-hook.js

Yet another JS code coverage tool that computes statement, line, function and branch coverage with module loader hooks to transparently add coverage when running tests. Supports all JS coverage use cases including unit tests, server side functional tests

/*
 Copyright (c) 2012, Yahoo! Inc.  All rights reserved.
 Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
 */

//EXPERIMENTAL code: do not rely on this in anyway until the docs say it is allowed

var path = require('path'),
    yuiRegexp = /yui-nodejs\.js$/;

module.exports = function (matchFn, transformFn, verbose) {
    return function (file) {
        if (!file.match(yuiRegexp)) {
            return;
        }
        var YMain = require(file),
            YUI,
            loaderFn,
            origGet;

        if (YMain.YUI) {
            YUI = YMain.YUI;
            loaderFn = YUI.Env && YUI.Env.mods && YUI.Env.mods['loader-base'] ? YUI.Env.mods['loader-base'].fn : null;
            if (!loaderFn) { return; }
            if (verbose) { console.log('Applying YUI load post-hook'); }
            YUI.Env.mods['loader-base'].fn = function (Y) {
                loaderFn.call(null, Y);
                origGet = Y.Get._exec;
                Y.Get._exec = function (data, url, cb) {
                    if (matchFn(url) || matchFn(path.resolve(url))) { //allow for relative paths as well
                        if (verbose) {
                            console.log('Transforming [' + url + ']');
                        }
                        try {
                            data = transformFn(data, url);
                        } catch (ex) {
                            console.error('Error transforming: ' + url + ' return original code');
                            console.error(ex.message || ex);
                            if (ex.stack) { console.error(ex.stack); }
                        }
                    }
                    return origGet.call(Y, data, url, cb);
                };
                return Y;
            };
        }
    };
};