755769 - Errors in mozApps onsuccess/onerror functions do not show up in Error Console

Status: RESOLVED WONTFIX

(Core Graveyard :: DOM: Apps, defect)

Description

[Ian Bicking (:ianbicking)]

When running code like this, one would expect the error to show up in the Error or Web Console, but it does not:

navigator.mozApps.getSelf().onsuccess = function () {
  console.log('In onsuccess');
  throw 'Broken';
};

This is demonstrated in http://app1.ianbicking.org/example-error.html if you click on the text "tryError4", or run tryError4() from the Web Console.

In another Bug 755553 I was told:

> I know we do not show in some cases exceptions that happen in synthesized DOM events. They don't even show in the error console.
>
> Does this error show in the Error Console for you? If it does, then it's most-likely an issue with the nsIScriptError that is sent - it might lack the inner/outer window IDs.
>
> For errors to display in the Web Console they need to have the originating inner and outer window IDs.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Is this just a case of XPConnect eating the exception because there is script on the stack when the event handler throws?  We've certainly had bug reports about that before.

How exactly is the onsuccess handler being invoked on the browser side?

Comment 2

[Ian Bicking (:ianbicking)]

In dom/base/Webapps.js it invokes Services.DOMRequest.fireSuccess(req, aResult).  The req object is what getSelf() returns, and is created with Services.DOMRequest.createRequest(window)

Comment 3

[Boris Zbarsky [:bzbarsky]]

Hmm.  That calls DispatchEvent from C++.  Olli, does it need to do some sort of extra context-pushing or JS stack-setting-aside before it does that?

Note that bug 503244 is the bug I was thinking of in comment 1.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

Dispatching events does cx pushing.
Not sure about JS stack handling. I'll test this - and if I don't, please remind me :)
(I'm worried about the performance of JS-stack-setting-aside)

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

Though, perhaps if the stack handling is pushed up to nsEventDispatcher, it isn't too bad.
https://bugzilla.mozilla.org/show_bug.cgi?id=503244#c45 could still be valid.

Comment 6

[Sylvestre Ledru [:Sylvestre]]

Core Graveyard / DOM: Apps is inactive. Closing all bugs in this component.