Sort algorithm: Magento checkout totals sorted wrongly causing wrong shipping tax calculation

Question

In Magento there is a functionality where you can define the order of total calculation by specifing before and after which totals a total should be run.

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Answer 1

EDIT: This answer is wrong. See the discussion in the comments.

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As Vinai noted, the problem is that the order function returns 0 even if the parameters are not equal. I modified the function to fall back on the string order of the keys as follows:

protected function _compareTotals($a, $b)
{
    $aCode = $a['_code'];
    $bCode = $b['_code'];
    if (in_array($aCode, $b['after']) || in_array($bCode, $a['before'])) {
        $res = -1;
    } elseif (in_array($bCode, $a['after']) || in_array($aCode, $b['before'])) {
        $res = 1;
    } else {
        $res = strcmp($aCode, $bCode); // was $res = 0 before
    }
    return $res;
}