Allow free order for custom payment

Question

My custom payment is blocked by this core function for free orders:

in app/code/core/Mage/Payment/Model/Method/Abstract.php

    public function isApplicableToQuote($quote, $checksBitMask) {
    ...
    if ($checksBitMask & self::CHECK_ZERO_TOTAL) {
        $total = $quote->getBaseSubtotal() + $quote->getShippingAddress()->getBaseShippingAmount();
        if ($total < 0.0001 && $this->getCode() != 'free'
            && !($this->canManageRecurringProfiles() && $quote->hasRecurringItems())
        ) {
            return false;
        }
    }

How can I bypass this? Do I need to overwrite the whole function?

Answer 1

You can overwrite the function and while calling parent, unset the CHECK_TOTAL_ZERO in the second parameter.

public function isApplicableToQuote($quote, $checksBitMask)
{
    return parent::isApplicableToQuote($quote, $checksBitMask & (~ self::CHECK_ZERO_TOTAL));
}