custom discount applied twice in magento 2 - magento2

Question

I have applied custom discount in magento 2.1 using this. Everything is working on local system but when I deploy the changes on server, discount get subtracted twice from the total.
Can any one any idea about this?
Sales.xml
<?xml version="1.0"?><config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Sales:etc/sales.xsd">
<section name="quote">
<group name="totals">
<item name="test_discount" instance="Namespace\Modulename\Model\Quote\Discount" sort_order="500"/>
</group>
</section>

Answer 1

To remove the custom discount applying twice in your summary .Just add below Lines
$items = $shippingAssignment->getItems();
if (!count($items)) {
return $this;
}
in the collect method. Once done, it will look like below.
public function collect(
\Magento\Quote\Model\Quote $quote,
\Magento\Quote\Api\Data\ShippingAssignmentInterface $shippingAssignment,
\Magento\Quote\Model\Quote\Address\Total $total
) {
$items = $shippingAssignment->getItems();
if (!count($items)) {
return $this;
}
parent::collect($quote, $shippingAssignment, $total);

Answer 2

This could be because of multishipping.
Magento collects totals per address. In the default scenario a quote has two addresses: A billing address and a shipping address.
I have not tried the example you linked, but afaiks the fee will be applied twice. For some reason this does not show up on the frontend, but I also had problems where a fee was applied twice, but somehow still showed up correctly on the frontend.
I assume when having a multiple shipping order, there is still only one billing address. Therefore the following snippet should fix the issue of having custom fees/discounts applied twice:
$address = $shippingAssignment->getShipping()->getAddress();
if($address->getAddressType() != 'billing'){
return $this;
}
Or, if you only want to apply the fee/charge for shipments with items:
$allBaseTotals = $total->getAllBaseTotalAmounts();
if(!isset($allBaseTotals['subtotal']) || $allBaseTotals['subtotal'] <= 0){
return $this;
}
This means the example file in the tutorial you linked would turn out like this:
app/code/Magestore/Webpos/Model/Total/Quote/Custom.php
/**
* #param \Magento\Quote\Model\Quote $quote
* #param \Magento\Quote\Api\Data\ShippingAssignmentInterface $shippingAssignment
* #param \Magento\Quote\Model\Quote\Address\Total $total
* #return $this|bool
*/
public function collect(
\Magento\Quote\Model\Quote $quote,
\Magento\Quote\Api\Data\ShippingAssignmentInterface $shippingAssignment,
\Magento\Quote\Model\Quote\Address\Total $total
)
{
parent::collect($quote, $shippingAssignment, $total);
$address = $shippingAssignment->getShipping()->getAddress();
if($address->getAddressType() != 'billing'){
return $this;
}
$baseDiscount = 10;
$discount = $this->_priceCurrency->convert($baseDiscount);
$total->addTotalAmount('customdiscount', -$discount);
$total->addBaseTotalAmount('customdiscount', -$baseDiscount);
$total->setBaseGrandTotal($total->getBaseGrandTotal() - $baseDiscount);
$quote->setCustomDiscount(-$discount);
return $this;
}
Edit:
It seems if($address->getAddressType() != 'billing'){ does not work as I thought it would.
I'm using if($address->getAddressType() == 'billing'){ for now as I'm not using multishipping.

Answer 3

Discount is calculated by address in quote, since there are two address billing and shipping that why is calculated twice.
you can set condition on either billing or shipping that only calculate for shipping address or billing address.
here just put this simple if statement (from nbjohan answer) at the start.
$address = $shippingAssignment->getShipping()->getAddress();
if($address->getAddressType() != 'billing'){
return $this;
}
now it will calculate only for one time.