Workaround for CakePHP bug #3389 ExceptionRenderer uses the wrong viewClass

ExceptionRendererFixed.php

<?php
/**
 * Exception Renderer Fixed
 * Angel S. Moreno (angelxmoreno@gmail.com)
 *
 * As per ticket #3389 (http://cakephp.lighthouseapp.com/projects/42648/tickets/3389-exceptionrenderer-uses-the-wrong-viewclass)
 * the ExceptionRenderer fails to use the proper view class when an exception is thrown in the AppController's beforeFilter.
 * This new ExceptionRenderer extends the original and updates the view class based on RequestHandlerComponent::params['ext'] and 
 * Router::extensions(). It assumes that when RequestHandlerComponent::params['ext'] is set and the extention is in the array of 
 * Router::extensions(), that the viewClass to use is prefixed by the extension being used. That being said, when the extenion is
 * xml the xmlView would be used. 
 * 
 * Instalation:
 * 1. Drop this file in your App/Lib/Error/ directory
 * 2. Edit your App/core.php file to use this Class to render your exceptions
 *       Configure::write('Exception', array(
 * 		'handler' => 'ErrorHandler::handleException',
 * 		'renderer' => 'ExceptionRendererFixed',
 * 		'log' => true
 * 	));
 */
App::uses('ExceptionRenderer', 'Error');

class ExceptionRendererFixed extends ExceptionRenderer {

    /**
     * Get the controller instance to handle the exception.
     * Override this method in subclasses to customize the controller used.
     * This method returns the built in `CakeErrorController` normally, or if an error is repeated
     * a bare controller will be used. Additionally, The method attempts to identify the proper viewClass
     * to use and sets it as the Coontroller::viewClass property.
     *
     * @param Exception $exception The exception to get a controller for.
     * @return Controller
     */
    protected function _getController($exception) {
        $controller = parent::_getController($exception);
        return $this->_fixViewClassProperty($controller, $this->_getRequest());
    }

    /**
     * @param Controller $controller The controller to update
     * @param CakeRequest $request a CakeRequest object to determine the viewClass to use
     * @return Controller
     */
    protected function _fixViewClassProperty(Controller $controller, CakeRequest $request) {
        if (!empty($request->params['ext']) and in_array($request->params['ext'], Router::extensions())) {
            $controller->viewClass = $request->params['ext'];
        }
        return $controller;
    }

    /**
     * Get the either a request object from the top of the stack or create a new one
     * 
     * @return CakeRequest 
     */
    protected function _getRequest() {
        if (!$request = Router::getRequest(true)) {
            $request = new CakeRequest();
        }
        return $request;
    }

}