Firefox throws error 'callback is not a function' when exiting

[lukeis]

Originally reported on Google Code with ID 2637

What steps will reproduce the problem?
1. Create a blank Firefox profile
2. Copy the webdriver XPI file
3. Run and then exit Firefox

What is the expected output? What do you see instead?

The following message is displayed in the log when exiting Firefox:

!!! error running onStopped callback: TypeError: callback is not a function

I browsed the other issues, but it seems this particular problem was never really addressed.
From what I can say, it however does not seem to prevent Firefox nor Selenium to run
correctly. Note I'm running Selenium on a headless server with xvfb.

Selenium version: trunk
OS: Debian 5.0.9 64 bits
Browser: Firefox
Brower version: iceweasel 3.6.23-1~bpo50+1

Reported by simpleentrepreneur on 2011-10-09 10:14:58

[lukeis]

Digging into the code and more specifically into httpd.js, it seems the stop(callback)
function is never called, which in turn generates the above error when the _notifyStopped()
function is called (this function is called from the onStopListening(socket, status)
function).

Indeed, the callback variable is from type 'BackstagePass' in that case, but it is
also 'undefined'. So checking for null solved the problem. As such, I would like to
suggest the following patch:

_notifyStopped: function()
{
  NS_ASSERT(this._stopCallback !== null, "double-notifying?");
  NS_ASSERT(!this._hasOpenConnections(), "should be done serving by now");

  var callback = this._stopCallback;
  this._stopCallback = null;
  try
  {
    if (callback !== null)
      callback();
    }
  }
  catch (e)
  {
    dump("!!! error running onStopped callback: " + e + "\n");
  }
}

But maybe the right way to fix it is to provide the right callback function...

Reported by simpleentrepreneur on 2011-10-09 10:23:36

[lukeis]

Well, I guess a more robust approach to my previous proposal would be:

if (typeof callback === "function") {
  callback();
}

Reported by simpleentrepreneur on 2011-10-09 12:06:58

[lukeis]

Reported by barancev on 2011-10-11 18:50:11

• Labels added: Browser-Firefox

[lukeis]

I've seen this as well. Perhaps we should update our httpd.js, and/or upstream this
fix to Mozilla?

Reported by jari.bakken on 2011-10-11 20:34:57

• Status changed: Accepted
• Labels added: Priority-Low, Component-WebDriver
• Labels removed: Priority-Medium

[lukeis]

Recent versions of httpd.js do not support ff3. As long as we're supporting ff3 I'd
suggest we just add an empty function to the requested callback. I agree it's confusing
the first 20 times one sees this error message ;)

Reported by kristian.rosenvold on 2011-10-12 06:44:23

[lukeis]

We don't need to support FF3 anymore. Is it worth to update httpd.js?

Reported by barancev on 2013-02-24 20:08:54

[lukeis]

Can we upgrade httpd.js to fix this issue? And another question: should we?

Reported by barancev on 2013-05-19 18:17:47

[lukeis]

The latest httpd.js has the same issue

Reported by barancev on 2014-11-07 07:51:53