Checkout Progress: Explicit Steps Needed

[astorm]

I was doing some varnish troubleshooting for a client, and we ran into a situation, using Magento 1.9.0.1, where the cart checkout progress blocks were not bypassing the varnish cache. We solved this by adding checkout to the turpentine blacklist -- but after investigating a bit I discovered the the approach turpentine takes to exclude checkout progress needs some tweaking. This pull request is lightly tested -- so consider this more a bug report than anything else.

Also, seems related to @craigcarnell's problems in this ticket
#455

The basic problem is the progressAction method doesn't do a full layout load (loadLayout)

#File: app/code/local/Mage/Checkout/controllers/OnepageController.php
public function progressAction()
{
    // previous step should never be null. We always start with billing and go forward
    $prevStep = $this->getRequest()->getParam('prevStep', false);

    if ($this->_expireAjax() || !$prevStep) {
        return null;
    }

    $layout = $this->getLayout();
    $update = $layout->getUpdate();
    /* Load the block belonging to the current step*/
    $update->load('checkout_onepage_progress_' . $prevStep);
    $layout->generateXml();
    $layout->generateBlocks();
    $output = $layout->getOutput();
    $this->getResponse()->setBody($output);

    return $output;
}

Instead, it specifically loads only the progress handle it needs

$prevStep = $this->getRequest()->getParam('prevStep', false);
//...
$update->load('checkout_onepage_progress_' . $prevStep);

Since loadLayout is never called, the checkout_onepage_progress handle(s) are never loaded into the layout and can't be applied. This includes the all important handle in turpentine_esi.xml

#File: app/design/frontend/base/default/layout/turpentine_esi.xml
<checkout_onepage_progress>
    <turpentine_cache_flag value="0"/>
</checkout_onepage_progress>

This pull request attempts a crude fix by being explicit about the progress handles to exclude. Another approach might be a pre-action dispatch listener that manually loads the checkout_onepage_progress handle in the layout -- I'm never sure how fancy to get in other people's projects :)

[miguelbalparda]

Thank you for the contribution @astorm, would you mind changing the branch target to devel instead of master?

[astorm]

Herp Derp, your strange modern ways frighten and confuse this frozen caveman developer. Closing this request, new request to devel here: #878

[miguelbalparda]

Perfect, thank you! We will review it and merge it as soon as possible.