Strange requestAction bug changing the page Content-Type

Today, I thought my current project was finished. But I had this bug report in my tracker from one of the beta-tester telling me that one of the page wasn't rendered properly.

It says that the code source was displayed on screen instead of being rendered as HTML. And only on Firefox.

And if that wasn't odd enough, even with the plethora of Firefox versions I got, I couldn't reproduce the bug on my side.

Turning off the debugger to debug

Then I had an idea. I turned off the debug mode, and was then able to reproduce the infamous bug.

As I initially supposed, there was something wrong with the Content-Type header. The Firebug Net Panel told me that it was set as text/plain while the developer toolbar insisted that it was text/html.

After some digging in my own code, I found the culprit. A requestAction() call I made as part of an update process. This requestAction was targeted at a .txt file.

I played a little with the debug value and found that for any value above 2, everything was working correctly, but if I set my value below that threshold, my whole view will get displayed as text/plain.

I couldn't quite explain why a debug value will have anything to with the view rendering. I even disabled the Debug Kit component, just to be sure.

Digging into cake world

And then I decided to follow the dispatch trace to find where the debug value was being used. After a long journey, I got to the respondAs method of the RequestHandler component.

And specifically, to that part:

if (Configure::read() < 2 && !defined('CAKEPHP_SHELL')) {
  $this->_header($header);
}

Ok, so there was my debug value. Exactly the code reponsible for my symptoms. Well, I still don't understand WHY someone wanted to add an header based on the debug value, but I could easily understand HOW it made my view that ugly.

The requestAction was being dispatched all along the way to its final action, firing the RequestHandler component on its way. Its extension being .txt, RequestHandler will fire its respondAs method and set the appropriate header.

Unfortunatly, setting such an header in a requestAction wasn't useful for the request, and additionnaly, it was messing with the primary view dispatch path.

Solution

I[ reported the bug](http://cakephp.lighthouseapp.com/projects/42648-cakephp/tickets/1445 -requestaction-may-change-the-current-layout-depending-on-debug-value) hoping for a fix in a future version. For the time being, I manually set the debug to 2 before calling my requestAction, and set it back to its previous value after in my app.

And for why it was only buggy on Firefox, it was caused by a double header definition. A first header was telling text/plain and a second one text/html. I guess Firefox uses the first one while other browsers the last. This is what made Firebug and the Developer Toolbar return different results too.