Mapstrace

A really simple library for printing human-readable stack-traces for combined, minified and/or compiled javascript files.

It assumes that your javascript file(s) have source maps (index.js -> index.js.map etc).

For example the following stack-trace:

TypeError: Cannot read property 'length' of null
    at $extend.index (/Users/janekp/Documents/wixe/trunk/server/api/web/index.js:103:7)
    at Application.main.wixe1.route.ctx.template (/Users/janekp/Documents/wixe/trunk/server/api/web/index.js:12:24)
    at Object.wixe.Server.handle (/Users/janekp/Documents/wixe/trunk/server/api/web/index.js:253:5)
    at Object.handle (/Users/janekp/Documents/wixe/trunk/server/api/web/index.js:197:8)
    at next (/Users/janekp/Documents/wixe/trunk/server/api/web/node_modules/connect/lib/proto.js:190:15)
    at Function.app.handle (/Users/janekp/Documents/wixe/trunk/server/api/web/node_modules/connect/lib/proto.js:198:3)
    at Server.app (/Users/janekp/Documents/wixe/trunk/server/api/web/node_modules/connect/lib/connect.js:66:31)
    at Server.EventEmitter.emit (events.js:91:17)
    at HTTPParser.parser.onIncoming (http.js:1785:12)
    at HTTPParser.parserOnHeadersComplete [as onHeadersComplete] (http.js:111:23)

becomes developer-friendly:

TypeError: Cannot read property 'length' of null:
    at 'if(x.length == 0) {' (.../trunk/server/api/src/RecipesPage.hx:45:25)
    at 'wixe.start(3000)' (.../trunk/server/api/src/Application.hx:18:26)
    at 'handler(ctx)' (.../server/api/src/wixe/Server.hx:290:23)
    at 'this.handle(req, res, next)' (.../server/api/src/wixe/Server.hx:306:37)
    ... (omitted 6 rows)

Installation and Dependencies

Install node.js for your platform

npm install source-map
npm install stack-trace

It can be used with or without Connect

var mapstrace = require('mapstrace');

// Connect
var connect = require('connect');
connect.createServer().use(connect.static('public')).use(mapstrace()).listen(3000);

// Stand-alone
mapstrace.build(err, true, function(result) {
    console.log(err.toString() + ':\n' + mapstrace.stringify(result));
});

The library can also be used to manually build a list of items and convert them into a string.

// err  - javascript Error object
// full - if true, then it will parse source files to fill missing fields.
// fn   - asynchronous callback that returns a list of items.
//        The list can contain objects and integers. Integers are used for unknown external items.
//        Every item has lineNumber, columnNumber, source and name fields.
mapstrace.build(err : Error, full : Bool, fn : Array -> Void) : Void;

// items  - A list of stack items (either numbers or objects).
// prefix - If not null then prefix is removed from paths. Optional, default is null
// limit  - The max number of path components. Optional, default is 5
// Returns a string.
mapstrace.stringify(items : Array, prefix : String, limit : Int) : String;