Get the full call stack trace of $http calls

So, you see, this issue is mostly because angular's $http sucks. Sorry about that.

Let's try to use the bluebird library, because it provides long stack traces.

Promise.longStackTraces();Promise.resolve($http.get('...'));

You get the following stack trace:

Possibly unhandled Error: [object Object]    at Promise$_rejectFromThenable (http://cdn.jsdelivr.net/bluebird/1.2.4/bluebird.js:4736:52)    at wrappedErrback (https://code.angularjs.org/1.3.0-beta.5/angular.js:11334:78)    at wrappedErrback (https://code.angularjs.org/1.3.0-beta.5/angular.js:11334:78)    at wrappedErrback (https://code.angularjs.org/1.3.0-beta.5/angular.js:11334:78)    at https://code.angularjs.org/1.3.0-beta.5/angular.js:11467:76    at Scope.$eval (https://code.angularjs.org/1.3.0-beta.5/angular.js:12418:28)    at Scope.$digest (https://code.angularjs.org/1.3.0-beta.5/angular.js:12230:31)    at Scope.$apply (https://code.angularjs.org/1.3.0-beta.5/angular.js:12522:24)    at done (https://code.angularjs.org/1.3.0-beta.5/angular.js:8207:45)    at completeRequest (https://code.angularjs.org/1.3.0-beta.5/angular.js:8412:7) 

(Plunker here.)

The most important line is the first: Possibly unhandled Error: [object Object].

Yep. An object is thrown, not a real Error object, with the stack property attached to it. For the reference, here is how to throw an error and keep its stack along with it: https://github.com/Ralt/newerror/blob/master/index.js

So, how to fix this? It depends on several decisions:

• Do you want to add a proper Promise lib that enables long stack traces?
• Do you want to use another xhr lib that throws correct errors?

If you want to add a real Promise lib, use bluebird. AFAIK, it is one of the few that provides long stack traces, and it is the fastest one out there.

For a proper xhr lib that throws real errors, I'm afraid you're out of luck there. Writing a custom one with the support for browsers you want isn't really hard though. With no IE8 support, this works (with bluebird):

function xhr(url) {    return new Promise(function(resolve, reject) {        var xhr = new XMLHttpRequest();        xhr.onload = function() {            resolve(xhr.responseText);        };        xhr.onerror = reject;        xhr.open('GET', url);        xhr.send();    });}

(Plunker here.)

As you can see, the stack trace is informative:

XHR requests are stacked in $http.pendingRequests array and are send later. Which is why you can't find a direct linked between where $http is called and where the actual XHR request is made.

If you want to know which function called $http you have to set a breakpoint in $http function.

It kinds of defeat the whole "XHR breakpoints" purpose in my opinion.

One option that came in my mind is to create a module for $http debugging that you can add it as a dependency in your main module whenever you need to debug $http calls. There a decorator for the $http service can be registered that will simply log the arguments of the call a forward it to the $http service. There a breakpoint can be set too.

I have created a simple working example here. I hope it will help.

Example $http logger decorator implementation:

var httpDebugging = angular.module('http-debugging', []);httpDebugging.decorator('$http', function ($delegate) {  var debugAware = function (fnCallback) {    return function () {        var result = fnCallback.apply(this, arguments);            console.log('$http decorator: ', arguments);        return result;    };     };   for(var prop in $delegate) {    if (angular.isFunction($delegate[prop])) {        $delegate[prop] = debugAware($delegate[prop]);    }  }  return $delegate;});