stacktrace-gps.js

(function(root, factory) {
    'use strict';
    // Universal Module Definition (UMD) to support AMD, CommonJS/Node.js, Rhino, and browsers.

    /* istanbul ignore next */
    if (typeof define === 'function' && define.amd) {
        define('stacktrace-gps', ['source-map', 'stackframe'], factory);
    } else if (typeof exports === 'object') {
        module.exports = factory(require('source-map/lib/source-map-consumer'), require('stackframe'));
    } else {
        root.StackTraceGPS = factory(root.SourceMap || root.sourceMap, root.StackFrame);
    }
}(this, function(SourceMap, StackFrame) {
    'use strict';

    /**
     * Make a X-Domain request to url and callback.
     *
     * @param {String} url
     * @returns {Promise} with response text if fulfilled
     */
    function _xdr(url) {
        return new Promise(function(resolve, reject) {
            var req = new XMLHttpRequest();
            req.open('get', url);
            req.onerror = reject;
            req.onreadystatechange = function onreadystatechange() {
                if (req.readyState === 4) {
                    if ((req.status >= 200 && req.status < 300) ||
                        (url.substr(0, 7) === 'file://' && req.responseText)) {
                        resolve(req.responseText);
                    } else {
                        reject(new Error('HTTP status: ' + req.status + ' retrieving ' + url));
                    }
                }
            };
            req.send();
        });

    }

    /**
     * Convert a Base64-encoded string into its original representation.
     * Used for inline sourcemaps.
     *
     * @param {String} b64str Base-64 encoded string
     * @returns {String} original representation of the base64-encoded string.
     */
    function _atob(b64str) {
        if (typeof window !== 'undefined' && window.atob) {
            return window.atob(b64str);
        } else {
            throw new Error('You must supply a polyfill for window.atob in this environment');
        }
    }

    function _parseJson(string) {
        if (typeof JSON !== 'undefined' && JSON.parse) {
            return JSON.parse(string);
        } else {
            throw new Error('You must supply a polyfill for JSON.parse in this environment');
        }
    }

    function _findFunctionName(source, lineNumber/*, columnNumber*/) {
        var syntaxes = [
            // {name} = function ({args}) TODO args capture
            /['"]?([$_A-Za-z][$_A-Za-z0-9]*)['"]?\s*[:=]\s*function\b/,
            // function {name}({args}) m[1]=name m[2]=args
            /function\s+([^('"`]*?)\s*\(([^)]*)\)/,
            // {name} = eval()
            /['"]?([$_A-Za-z][$_A-Za-z0-9]*)['"]?\s*[:=]\s*(?:eval|new Function)\b/,
            // fn_name() {
            /\b(?!(?:if|for|switch|while|with|catch)\b)(?:(?:static)\s+)?(\S+)\s*\(.*?\)\s*\{/,
            // {name} = () => {
            /['"]?([$_A-Za-z][$_A-Za-z0-9]*)['"]?\s*[:=]\s*\(.*?\)\s*=>/
        ];
        var lines = source.split('\n');

        // Walk backwards in the source lines until we find the line which matches one of the patterns above
        var code = '';
        var maxLines = Math.min(lineNumber, 20);
        for (var i = 0; i < maxLines; ++i) {
            // lineNo is 1-based, source[] is 0-based
            var line = lines[lineNumber - i - 1];
            var commentPos = line.indexOf('//');
            if (commentPos >= 0) {
                line = line.substr(0, commentPos);
            }

            if (line) {
                code = line + code;
                var len = syntaxes.length;
                for (var index = 0; index < len; index++) {
                    var m = syntaxes[index].exec(code);
                    if (m && m[1]) {
                        return m[1];
                    }
                }
            }
        }
        return undefined;
    }

    function _ensureSupportedEnvironment() {
        if (typeof Object.defineProperty !== 'function' || typeof Object.create !== 'function') {
            throw new Error('Unable to consume source maps in older browsers');
        }
    }

    function _ensureStackFrameIsLegit(stackframe) {
        if (typeof stackframe !== 'object') {
            throw new TypeError('Given StackFrame is not an object');
        } else if (typeof stackframe.fileName !== 'string') {
            throw new TypeError('Given file name is not a String');
        } else if (typeof stackframe.lineNumber !== 'number' ||
            stackframe.lineNumber % 1 !== 0 ||
            stackframe.lineNumber < 1) {
            throw new TypeError('Given line number must be a positive integer');
        } else if (typeof stackframe.columnNumber !== 'number' ||
            stackframe.columnNumber % 1 !== 0 ||
            stackframe.columnNumber < 0) {
            throw new TypeError('Given column number must be a non-negative integer');
        }
        return true;
    }

    function _findSourceMappingURL(source) {
        var sourceMappingUrlRegExp = /\/\/[#@] ?sourceMappingURL=([^\s'"]+)\s*$/mg;
        var lastSourceMappingUrl;
        var matchSourceMappingUrl;
        while (matchSourceMappingUrl = sourceMappingUrlRegExp.exec(source)) { // jshint ignore:line
            lastSourceMappingUrl = matchSourceMappingUrl[1];
        }
        if (lastSourceMappingUrl) {
            return lastSourceMappingUrl;
        } else {
            throw new Error('sourceMappingURL not found');
        }
    }

    function _extractLocationInfoFromSourceMapSource(stackframe, sourceMapConsumer, sourceCache) {
        return new Promise(function(resolve, reject) {
            var loc = sourceMapConsumer.originalPositionFor({
                line: stackframe.lineNumber,
                column: stackframe.columnNumber
            });

            if (loc.source) {
                // cache mapped sources
                var mappedSource = sourceMapConsumer.sourceContentFor(loc.source);
                if (mappedSource) {
                    sourceCache[loc.source] = mappedSource;
                }

                resolve(
                    // given stackframe and source location, update stackframe
                    new StackFrame({
                        functionName: loc.name || stackframe.functionName,
                        args: stackframe.args,
                        fileName: loc.source,
                        lineNumber: loc.line,
                        columnNumber: loc.column
                    }));
            } else {
                reject(new Error('Could not get original source for given stackframe and source map'));
            }
        });
    }

    /**
     * @constructor
     * @param {Object} opts
     *      opts.sourceCache = {url: "Source String"} => preload source cache
     *      opts.sourceMapConsumerCache = {/path/file.js.map: SourceMapConsumer}
     *      opts.offline = True to prevent network requests.
     *              Best effort without sources or source maps.
     *      opts.ajax = Promise returning function to make X-Domain requests
     */
    return function StackTraceGPS(opts) {
        if (!(this instanceof StackTraceGPS)) {
            return new StackTraceGPS(opts);
        }
        opts = opts || {};

        this.sourceCache = opts.sourceCache || {};
        this.sourceMapConsumerCache = opts.sourceMapConsumerCache || {};

        this.ajax = opts.ajax || _xdr;

        this._atob = opts.atob || _atob;

        this._get = function _get(location) {
            return new Promise(function(resolve, reject) {
                var isDataUrl = location.substr(0, 5) === 'data:';
                if (this.sourceCache[location]) {
                    resolve(this.sourceCache[location]);
                } else if (opts.offline && !isDataUrl) {
                    reject(new Error('Cannot make network requests in offline mode'));
                } else {
                    if (isDataUrl) {
                        // data URLs can have parameters.
                        // see http://tools.ietf.org/html/rfc2397
                        var supportedEncodingRegexp =
                            /^data:application\/json;([\w=:"-]+;)*base64,/;
                        var match = location.match(supportedEncodingRegexp);
                        if (match) {
                            var sourceMapStart = match[0].length;
                            var encodedSource = location.substr(sourceMapStart);
                            var source = this._atob(encodedSource);
                            this.sourceCache[location] = source;
                            resolve(source);
                        } else {
                            reject(new Error('The encoding of the inline sourcemap is not supported'));
                        }
                    } else {
                        var xhrPromise = this.ajax(location, {method: 'get'});
                        // Cache the Promise to prevent duplicate in-flight requests
                        this.sourceCache[location] = xhrPromise;
                        xhrPromise.then(resolve, reject);
                    }
                }
            }.bind(this));
        };

        /**
         * Creating SourceMapConsumers is expensive, so this wraps the creation of a
         * SourceMapConsumer in a per-instance cache.
         *
         * @param {String} sourceMappingURL = URL to fetch source map from
         * @param {String} defaultSourceRoot = Default source root for source map if undefined
         * @returns {Promise} that resolves a SourceMapConsumer
         */
        this._getSourceMapConsumer = function _getSourceMapConsumer(sourceMappingURL, defaultSourceRoot) {
            return new Promise(function(resolve, reject) {
                if (this.sourceMapConsumerCache[sourceMappingURL]) {
                    resolve(this.sourceMapConsumerCache[sourceMappingURL]);
                } else {
                    var sourceMapConsumerPromise = new Promise(function(resolve, reject) {
                        return this._get(sourceMappingURL).then(function(sourceMapSource) {
                            if (typeof sourceMapSource === 'string') {
                                sourceMapSource = _parseJson(sourceMapSource.replace(/^\)\]\}'/, ''));
                            }
                            if (typeof sourceMapSource.sourceRoot === 'undefined') {
                                sourceMapSource.sourceRoot = defaultSourceRoot;
                            }

                            resolve(new SourceMap.SourceMapConsumer(sourceMapSource));
                        }, reject);
                    }.bind(this));
                    this.sourceMapConsumerCache[sourceMappingURL] = sourceMapConsumerPromise;
                    resolve(sourceMapConsumerPromise);
                }
            }.bind(this));
        };

        /**
         * Given a StackFrame, enhance function name and use source maps for a
         * better StackFrame.
         *
         * @param {StackFrame} stackframe object
         * @returns {Promise} that resolves with with source-mapped StackFrame
         */
        this.pinpoint = function StackTraceGPS$$pinpoint(stackframe) {
            return new Promise(function(resolve, reject) {
                this.getMappedLocation(stackframe).then(function(mappedStackFrame) {
                    function resolveMappedStackFrame() {
                        resolve(mappedStackFrame);
                    }

                    this.findFunctionName(mappedStackFrame)
                        .then(resolve, resolveMappedStackFrame)
                        ['catch'](resolveMappedStackFrame);
                }.bind(this), reject);
            }.bind(this));
        };

        /**
         * Given a StackFrame, guess function name from location information.
         *
         * @param {StackFrame} stackframe
         * @returns {Promise} that resolves with enhanced StackFrame.
         */
        this.findFunctionName = function StackTraceGPS$$findFunctionName(stackframe) {
            return new Promise(function(resolve, reject) {
                _ensureStackFrameIsLegit(stackframe);
                this._get(stackframe.fileName).then(function getSourceCallback(source) {
                    var lineNumber = stackframe.lineNumber;
                    var columnNumber = stackframe.columnNumber;
                    var guessedFunctionName = _findFunctionName(source, lineNumber, columnNumber);
                    // Only replace functionName if we found something
                    if (guessedFunctionName) {
                        resolve(new StackFrame({
                            functionName: guessedFunctionName,
                            args: stackframe.args,
                            fileName: stackframe.fileName,
                            lineNumber: lineNumber,
                            columnNumber: columnNumber
                        }));
                    } else {
                        resolve(stackframe);
                    }
                }, reject)['catch'](reject);
            }.bind(this));
        };

        /**
         * Given a StackFrame, seek source-mapped location and return new enhanced StackFrame.
         *
         * @param {StackFrame} stackframe
         * @returns {Promise} that resolves with enhanced StackFrame.
         */
        this.getMappedLocation = function StackTraceGPS$$getMappedLocation(stackframe) {
            return new Promise(function(resolve, reject) {
                _ensureSupportedEnvironment();
                _ensureStackFrameIsLegit(stackframe);

                var sourceCache = this.sourceCache;
                var fileName = stackframe.fileName;
                this._get(fileName).then(function(source) {
                    var sourceMappingURL = _findSourceMappingURL(source);
                    var isDataUrl = sourceMappingURL.substr(0, 5) === 'data:';
                    var defaultSourceRoot = fileName.substring(0, fileName.lastIndexOf('/') + 1);

                    if (sourceMappingURL[0] !== '/' && !isDataUrl && !(/^https?:\/\/|^\/\//i).test(sourceMappingURL)) {
                        sourceMappingURL = defaultSourceRoot + sourceMappingURL;
                    }

                    return this._getSourceMapConsumer(sourceMappingURL, defaultSourceRoot)
                        .then(function(sourceMapConsumer) {
                            return _extractLocationInfoFromSourceMapSource(stackframe, sourceMapConsumer, sourceCache)
                                .then(resolve)['catch'](function() {
                                resolve(stackframe);
                            });
                        });
                }.bind(this), reject)['catch'](reject);
            }.bind(this));
        };
    };
}));