vows/lib/assert/error.js

Asynchronous BDD & continuous integration for node.js

/**
This software contains code adapted from Mocha
(https://github.com/visionmedia/mocha) by TJ Holowaychuk
and is used herein under the following MIT license:

Copyright (c) 2011-2012 TJ Holowaychuk <tj@vision-media.ca>

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
'Software'), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

var stylize = require('../vows/console').stylize;
var inspect = require('../vows/console').inspect;
var diff = require('diff');

/**
 * Pad the given `str` to `len`.
 *
 * @param {String} str
 * @param {String} len
 * @return {String}
 * @api private
 */

function pad(str, len) {
  str = String(str);
  return Array(len - str.length + 1).join(' ') + str;
}

/**
 * Color lines for `str`, using the color `name`.
 *
 * @param {String} name
 * @param {String} str
 * @return {String}
 * @api private
 */

function styleLines(str, name) {
  return str.split('\n').map(function(str){
    return stylize(str, name);
  }).join('\n');
}

/**
 * Return a character diff for `err`.
 *
 * @param {Error} err
 * @return {String}
 * @api private
 */

function errorDiff(err, type) {
  return diff['diff' + type](err.expected, err.actual).map(function(str){
    if (/^(\n+)$/.test(str.value)) str.value = Array(++RegExp.$1.length).join('<newline>');
    if (str.added) return styleLines(str.value, 'green');
    if (str.removed) return styleLines(str.value, 'red');
    return str.value;
  }).join('');
}

function extractPathFromStack(stack) {
    var regex = /\((.*?[a-zA-Z0-9._-]+\.(?:js|coffee))(:\d+):\d+\)/;
    return stack.match(regex);
}

/*
 Do not override .toString() when this.stack is used,
 otherwise this will end in an endless recursive call...
 See issue https://github.com/cloudhead/vows/issues/278#issuecomment-22837493
*/
require('assert').AssertionError.prototype.toStringEx = function () {
    var that = this,
        source;

    if (this.stack) {
        source = extractPathFromStack(this.stack);
    }

    function parse(str) {
        var actual = that.actual,
            expected = that.expected,
            msg, len;

        if (
            'string' === typeof actual &&
            'string' === typeof expected
        ) {
            len = Math.max(actual.length, expected.length);

            if (len < 20) msg = errorDiff(that, 'Chars');
            else msg = errorDiff(that, 'Words');

            // linenos
            var lines = msg.split('\n');
            if (lines.length > 4) {
                var width = String(lines.length).length;
                msg = lines.map(function(str, i){
                    return pad(++i, width) + ' |' + ' ' + str;
                }).join('\n');
            }

            // legend
            msg = '\n'
                + stylize('actual', 'green')
                + ' '
                + stylize('expected', 'red')
                + '\n\n'
                + msg
                + '\n';

            // indent
            msg = msg.replace(/^/gm, '      ');

            return msg;
        }

        actual = inspect(actual, {showHidden: actual instanceof Error});

        if (expected instanceof Function) {
            expected = expected.name;
        }
        else {
            expected = inspect(expected, {showHidden: actual instanceof Error});
        }

        return str.replace(/{actual}/g,   actual).
                   replace(/{operator}/g, stylize(that.operator, 'bold')).
                   replace(/{expected}/g, expected);
    }

    if (this.message) {
        var msg = stylize(parse(this.message), 'yellow');
      	if (source) {
      		  msg += stylize(' // ' + source[1] + source[2], 'grey');
      	}
        return msg;
    } else {
        return stylize([
            this.expected,
            this.operator,
            this.actual
        ].join(' '), 'yellow');
    }
};