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) {
                        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*/) {
        // function {name}({args}) m[1]=name m[2]=args
        var reFunctionDeclaration = /function\s+([^(]*?)\s*\(([^)]*)\)/;
        // {name} = function ({args}) TODO args capture
        var reFunctionExpression = /['"]?([$_A-Za-z][$_A-Za-z0-9]*)['"]?\s*[:=]\s*function\b/;
        // {name} = eval()
        var reFunctionEvaluation = /['"]?([$_A-Za-z][$_A-Za-z0-9]*)['"]?\s*[:=]\s*(?:eval|new Function)\b/;
        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);
        var m;
        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;
                m = reFunctionExpression.exec(code);
                if (m && m[1]) {
                    return m[1];
                }
                m = reFunctionDeclaration.exec(code);
                if (m && m[1]) {
                    return m[1];
                }
                m = reFunctionEvaluation.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 m = /\/\/[#@] ?sourceMappingURL=([^\s'"]+)\s*$/.exec(source);
        if (m && m[1]) {
            return m[1];
        } else {
            throw new Error('sourceMappingURL not found');
        }
    }

    function _extractLocationInfoFromSourceMap(rawSourceMap, args, lineNumber, columnNumber, sourceCache) {
        var mapConsumer = new SourceMap.SourceMapConsumer(rawSourceMap);

        var loc = mapConsumer.originalPositionFor({
            line: lineNumber,
            column: columnNumber
        });

        var mappedSource = mapConsumer.sourceContentFor(loc.source);
        if (mappedSource) {
            sourceCache[loc.source] = mappedSource;
        }

        return new StackFrame(loc.name, args, loc.source, loc.line, loc.column);
    }

    /**
     * @constructor
     * @param {Object} opts
     *      opts.sourceCache = {url: "Source String"} => preload source cache
     *      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.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));
        };

        /**
         * 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 guessedFunctionName = _findFunctionName(source, stackframe.lineNumber, stackframe.columnNumber);
                    resolve(new StackFrame(guessedFunctionName,
                        stackframe.args,
                        stackframe.fileName,
                        stackframe.lineNumber,
                        stackframe.columnNumber));
                }, 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 base = fileName.substring(0, fileName.lastIndexOf('/') + 1);

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

                    this._get(sourceMappingURL).then(function(map) {
                        var line = stackframe.lineNumber;
                        var column = stackframe.columnNumber;

                        if (typeof map === 'string') {
                            map = _parseJson(map.replace(/^\)\]\}'/, ''));
                        }

                        if (typeof map.sourceRoot === 'undefined') {
                            map.sourceRoot = base;
                        }

                        resolve(_extractLocationInfoFromSourceMap(map, stackframe.args, line, column, sourceCache));
                    }, reject)['catch'](reject);
                }.bind(this), reject)['catch'](reject);
            }.bind(this));
        };
    };
}));