Topological Sorting of Total Models

In Magento we have the problem, that Mage_Sales_Model_Config_Ordered should sort a bunch of items topological, but unfortunately it doesn't.

I encountered the problem with wrongly sorted totals a few times, but now it was enough. I wrote a blog article about it. Thanks to @Daniel_Sloof, he pointed me to more informations from @VinaiKopp. I then found a question on Stackoverflow from @s3lf.

After reading all this I decided to implement a module which fixes this. Thanks to Dan Mossop a topo sort library for PHP already exists. But it was untested, so I decided to write a few tests for it and then write a Magento module. But we are all lazy and why write tests, if already someone else did. So lets use the library from Marc J. Schmidt.

Unfortunately is the Magento bug in an abstract class, therefore we have to overwrite a core file in app/code/local

Installation

1. Install the library dependency

Install the library fro Marc J. Schmidt as a composer dependency by running composer require marcj/topsort

2. Install the Magento part

Install this repo via modman or copy the code from src/app/code/local/Mage/Sales/Model/Config/Ordered.php to app/code/local/Mage/Sales/Model/Config/Ordered.php manually.

What this module does

This module takes a library for topological sorting and fixes the broken algorithm to sort lots of stuff which has before and after dependencies, like totals in quote, order and creditmemo.

#License My work is under BSD 3-clause. But be careful, I only changed the \Mage_Sales_Model_Config_Ordered::_getSortedCollectorCodes implementation and added the topological sorting to the class. The rest is copied from Magento version 1.9.1