I found a nice new, rarely trigger Magento bug.

In one of our projects, we have an example file to create new products:

data-upgrade-example-new-product-import.php


Beside this we had data scripts:

data-install-1.0.1.php


Unfortunately data-upgrade-1.0.5-1.0.6.php didn't fire.

It took me a while, but I found the problem:

// \Mage_Core_Model_Resource_Setup::_getModifySqlFiles
protected function _getModifySqlFiles($actionType,$fromVersion, $toVersion,$arrFiles)
{
$arrRes = array(); switch ($actionType) {

// ...

uksort($arrFiles, 'version_compare'); foreach ($arrFiles as $version =>$file) {
$versionInfo = explode('-',$version);

// In array must be 2 elements: 0 => version from, 1 => version to
if (count($versionInfo)!=2) { break; }  in $arrFiles we find an array with all files in the data dir which match a certain regex in \Mage_Core_Model_Resource_Setup::_getAvailableDataFiles. In short, when the files starts with data-.

The problem is, that data-upgrade-example-new-product-import.php doesn't meet the if (count($versionInfo)!=2) check and then break is called, which kills the complete loop, but should only be continue;. So either we hack the core or rename the data-upgrade-example-new-product-import.php, I decided for renaming. Missing data, failed transactions and unassigned products Last week my job was to port a module back from Magento 1.9 to Magento 1.4. Allowed core hacks In the end the only real problem I had, was that Mage_Core_Model_Resource_Db_Abstract doesn't exist already, therefore I created the file in core with the content: <?php class Mage_Core_Model_Resource_Db_Abstract extends Mage_Core_Model_Mysql4_Abstract {}  If you ask me, this is one of the very rare cases, where a core hack is ok. When Magento is updated, the file is overwrittten and exists then. If you create the file in community or local, this doesn't happen automatically. Raised auto_increment but missing data - no quote I copied the module from Magento 1.9 to 1.4 without problems, created the core file and tested it. On my first tests, I didn't get a quote item. Whatever I did, my cart was empty. The bad thing I discovered was, that Magento didn't even create a quote. sales_flat_quote is empty. But the auto_increment value raises by 1. I tried to google it, but googleing for INSERT is ignored or quote is not written didn't help a lot. After one day of searching, I found a MySQL forums post which described the same behaviour. The answer was thankfully there to. What happened? 1. Transaction is started 2. Quote is written to the database 3. Autoincrement is increased 4. Something fails 5. Rollback. Ok. But what fails? In the end I discovered, that the Problem was a killed model rewrite, which leads to an unset quote_id on the quote_payment. I have no clue why this happend. But after deleting the model and setting up the old rewrite this problem was solved. Quote item in database, but cart empty I thought I was done. Said the client it is only a matter of minutes, but the next test still fails. The cart is still empty. I started investigating again. The quote was created, the item written - and then deleted. I learned, that when a collection is loaded all products are assigned to the quote items. If the product doesn't exist, the quote item is deleted. So far so understandable. \Mage_Sales_Model_Resource_Quote_Item_Collection::_afterLoad \Mage_Sales_Model_Resource_Quote_Item_Collection::_assignProducts$product = $productCollection->getItemById($item->getProductId());
if ($product) { // [...] } else {$item->isDeleted(true);
$recollectQuote = true; }  Long story short: The collection is loaded from the flat tables (if activated). My product was missing there. $productCollection = Mage::getModel('catalog/product')->getCollection()
->setStoreId($this->getStoreId()) ->addIdFilter($this->_productIds)


Unfortunately I forgot to assign the product to the desired website. We don't test if the product is available on the website, so no error is thrown on adding it to the cart and without happening anything the item is deleted, before anyone even sees it.

Hope that helps someone finding such weird and hard to trace bugs.

TL;DR

Install Topological Sort to fix the sorting algorithm.

Problem

Mage_Weee is a module which is needed in Magento to calculate the so called Waste Electrical and Electronic Equipment Directive. It is a tax in Europe for electronic stuff, so that it is already paid, when you throws it away. Don't ask me. We don't sell any kind of electric stuff, so it is a good decision to remove the module.

<!-- app/etc/modules/zzzzzz_DeactivatedModules.xml-->
<?xml version="1.0"?>
<config>
<modules>
<Mage_Weee>
<active>false</active>
</Mage_Weee>
</modules>
</config>


What happens then was very irritating for me.

Before:

After:

You might sense the miscalculation of the tax. Our tax settings are still correct and everything is fine, but the tax is added to the price, instead of being included.

Easiest fix here is to just NOT deactivate Mage_Weee, but this is unsatisfying. So I dig deeper (and have already an idea, what happens):

Magento total models

Magento is calculating all the stuff in quote and order with total models. You can check what total models are called in

\Mage_Sales_Model_Quote_Address::collectTotals
foreach ($this->getTotalCollector()->getCollectors() as$model) {
echo get_class($model) . "\n";$model->collect(\$this);
}


• Mage_Sales_Model_Quote_Address_Total_Nominal
• Mage_Sales_Model_Quote_Address_Total_Subtotal
• Mage_Sales_Model_Quote_Address_Total_Msrp
• Mage_SalesRule_Model_Quote_Freeshipping
• Mage_Tax_Model_Sales_Total_Quote_Subtotal
• Mage_Weee_Model_Total_Quote_Weee
• Mage_Sales_Model_Quote_Address_Total_Shipping
• Mage_Tax_Model_Sales_Total_Quote_Shipping
• Mage_SalesRule_Model_Quote_Discount
• Mage_Tax_Model_Sales_Total_Quote_Tax
• Mage_Sales_Model_Quote_Address_Total_Grand

• Mage_SalesRule_Model_Quote_Freeshipping
• Mage_Tax_Model_Sales_Total_Quote_Subtotal
• Mage_Tax_Model_Sales_Total_Quote_Shipping
• Mage_SalesRule_Model_Quote_Discount
• Mage_Tax_Model_Sales_Total_Quote_Tax
• Mage_Sales_Model_Quote_Address_Total_Msrp
• Mage_Sales_Model_Quote_Address_Total_Nominal
• Mage_Sales_Model_Quote_Address_Total_Subtotal
• Mage_Sales_Model_Quote_Address_Total_Shipping
• Mage_Sales_Model_Quote_Address_Total_Grand

As you can see, the order is totally different. I'm cleaning up the list a little bit:

WITH WeeeWithOUT Weee
Mage_Tax_Model_Sales_Total_Quote_Subtotal Mage_Tax_Model_Sales_Total_Quote_Shipping

I think (I didn't check it yet), that the Mage_Tax totals expect, that the Mage_Sales already ran and collected all the sums, etc. So when you are changing the order from first Mage_Sales, then Mage_Tax, you get wrong results.

Ordering multiple dependend nodes in a graph is a hard problem

The problem lays in the ordering algorithm. All the totals have a before and after in their definition.

<!-- app/code/core/Mage/Tax/etc/config.xml:160 -->
<sales>
<quote>
<totals>
<tax_subtotal>
<class>tax/sales_total_quote_subtotal</class>
<after>freeshipping</after>
<before>tax,discount</before>
</tax_subtotal>
<tax_shipping>
<class>tax/sales_total_quote_shipping</class>
<after>shipping,tax_subtotal</after>
<before>tax,discount</before>
</tax_shipping>
[...]


All the ordering is done here:
\Mage_Sales_Model_Config_Ordered and this is buggy.

How to solve it the great way

The hard solution for this is:

1. Implement a real graph algorithm which solves all the dependencies and orders the total models correct
2. Play with all the before and after nodes until the order is correct.

I neither implemented a cool algorithm yet (or looked it up) to solve the problem, nor did I play with the values until everything is fine. I'm staying with the solution: Not deactivating Mage_Weee for the moment.