TotalsCollector ignores discount_amount

[kassner]

Hi,

I'm trying to programatically figure out the final price for a specific set of items without having to add them to the user cart before (mostly to avoid messing up customer's session and accidentally adding products their don't want).

I'm using the following code:

$quote = $this->quoteFactory->create();
$product = $this->productRepository->get('my-sku');
$quote->addProduct($product, 1);
// add more products here
$quote->getShippingAddress(); # otherwise $quote->getAllAddresses() returns empty
$quote->setTotalsCollectedFlag(false);
$quote->collectTotals();
var_dump($quote->getTotals());

But, it looks like \Magento\Quote\Model\Quote\TotalsCollector::collect is ignoring the discount_amount, since the $quote->getTotals() does not report the discount key at all.

Interesting enough, the grand_total is mentioned with discount (10.00, 10800 => 10790). Seems that just adding the following line after $addressTotal fixes the issue (and it was how I generated the "expected result" section later on).

$total->setDiscountAmount($addressTotal->getDiscountAmount());

Preconditions

1. Magento 2.1.1;
2. Enabled cart promotion giving 10% off for my-sku, no customer group restrictions;
3. Sales rules reindexed (EE);

Steps to reproduce

1. Run the php code mentioned above inside a controller or a Test app;

Expected result

1. $quote->getTotals() should return the discount key with the giving discount for the applied rules.

/var/www/html/app/code/Vendor/Price/Model/Calculator.php:61:
array (size=5)
  'subtotal' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2067]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=5)
          'code' => string 'subtotal' (length=8)
          'title' => 
            object(Magento\Framework\Phrase)[2093]
              ...
          'value' => float 10800
          'value_incl_tax' => float 10800
          'value_excl_tax' => float 10800
  'shipping' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2096]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=3)
          'code' => string 'shipping' (length=8)
          'title' => 
            object(Magento\Framework\Phrase)[2085]
              ...
          'value' => float 0
  'discount' => 
    object(Magento\Quote\Model\Quote\Address\Total)[1671]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=3)
          'code' => string 'discount' (length=8)
          'title' => 
            object(Magento\Framework\Phrase)[2095]
              ...
          'value' => float -10
  'tax' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2101]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=5)
          'code' => string 'tax' (length=3)
          'title' => 
            object(Magento\Framework\Phrase)[2098]
              ...
          'full_info' => 
            array (size=0)
              ...
          'value' => float 0
          'area' => string 'taxes' (length=5)
  'grand_total' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2105]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=4)
          'code' => string 'grand_total' (length=11)
          'title' => 
            object(Magento\Framework\Phrase)[2104]
              ...
          'value' => float 10790
          'area' => string 'footer' (length=6)

Actual result

1. $quote->getTotals() does not contain the discount key.

/var/www/html/app/code/Vendor/Price/Model/Calculator.php:61:
array (size=4)
  'subtotal' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2068]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=5)
          'code' => string 'subtotal' (length=8)
          'title' => 
            object(Magento\Framework\Phrase)[2096]
              ...
          'value' => float 10800
          'value_incl_tax' => float 10800
          'value_excl_tax' => float 10800
  'shipping' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2097]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=3)
          'code' => string 'shipping' (length=8)
          'title' => 
            object(Magento\Framework\Phrase)[2086]
              ...
          'value' => float 0
  'tax' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2094]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=5)
          'code' => string 'tax' (length=3)
          'title' => 
            object(Magento\Framework\Phrase)[1672]
              ...
          'full_info' => 
            array (size=0)
              ...
          'value' => float 0
          'area' => string 'taxes' (length=5)
  'grand_total' => 
    object(Magento\Quote\Model\Quote\Address\Total)[2104]
      protected 'totalAmounts' => null
      protected 'baseTotalAmounts' => null
      protected '_data' => 
        array (size=4)
          'code' => string 'grand_total' (length=11)
          'title' => 
            object(Magento\Framework\Phrase)[2103]
              ...
          'value' => float 10790
          'area' => string 'footer' (length=6)

Thanks.

[SerhiyShkolyarenko]

Hi @kassner!
As far as I understood you try to calculate totals without setting billing and shipping address. It's incorrect approach because taxes, shipping rates, rules may depend on this data.
You need a service like \Magento\Checkout\Model\TotalsInformationManagement::calculate() which will work with inactive quote.

[kassner]

@SerhiyShkolyarenko well, that method does exactly the same thing I described, so I probably will not return the discount row either way.

Still, I have a shipping address object ("created" with $quote->getShippingAddress(), since other approaches won't work before saving everything), but it is empty. Anyway, that should not be a limitation to calculate the discount of others rules, the same way rules for payment methods do not avoid coupon rules to be calculated in the cart.

[SerhiyShkolyarenko]

OK, let look at example: United States, tax rate in Idaho is 6.03%, tax rate in Nevada is 7.98%; Base price(without tax) of the item is $1000. Calculating totals makes sense when you know billing/shipping address, and hence tax amount and price before discount.
If you write extension for a certain country where tax rate is equal for every region or the prices include taxes, then you should write a service similar to \Magento\Checkout\Model\TotalsInformationManagement::calculate(). it is used in our REST API and returns a discount. Here is an example of output:

<?xml version="1.0"?>
<response>
  <grand_total>16.2</grand_total>
  <base_grand_total>16.2</base_grand_total>
  <subtotal>6.2</subtotal>
  <base_subtotal>6.2</base_subtotal>
  <discount_amount>0</discount_amount>
  <base_discount_amount>0</base_discount_amount>
  <subtotal_with_discount>6.2</subtotal_with_discount>
  <base_subtotal_with_discount>6.2</base_subtotal_with_discount>
  <shipping_amount>10</shipping_amount>
  <base_shipping_amount>10</base_shipping_amount>
  <shipping_discount_amount>0</shipping_discount_amount>
  <base_shipping_discount_amount>0</base_shipping_discount_amount>
  <tax_amount>0</tax_amount>
  <base_tax_amount>0</base_tax_amount>
  <weee_tax_applied_amount></weee_tax_applied_amount>
  <shipping_tax_amount>0</shipping_tax_amount>
  <base_shipping_tax_amount>0</base_shipping_tax_amount>
  <subtotal_incl_tax>6.2</subtotal_incl_tax>
  <base_subtotal_incl_tax>6.2</base_subtotal_incl_tax>
  <shipping_incl_tax>10</shipping_incl_tax>
  <base_shipping_incl_tax>10</base_shipping_incl_tax>
  <base_currency_code>USD</base_currency_code>
  <quote_currency_code>USD</quote_currency_code>
  <items_qty>2</items_qty>
  <items>
    <item>
      <item_id>11</item_id>
      <price>3.1</price>
      <base_price>3.1</base_price>
      <qty>2</qty>
      <row_total>6.2</row_total>
      <base_row_total>6.2</base_row_total>
      <row_total_with_discount>0</row_total_with_discount>
      <tax_amount>0</tax_amount>
      <base_tax_amount>0</base_tax_amount>
      <tax_percent>0</tax_percent>
      <discount_amount>0</discount_amount>
      <base_discount_amount>0</base_discount_amount>
      <discount_percent>0</discount_percent>
      <price_incl_tax>3.1</price_incl_tax>
      <base_price_incl_tax>3.1</base_price_incl_tax>
      <row_total_incl_tax>6.2</row_total_incl_tax>
      <base_row_total_incl_tax>6.2</base_row_total_incl_tax>
      <options>[]</options>
      <weee_tax_applied_amount></weee_tax_applied_amount>
      <weee_tax_applied></weee_tax_applied>
      <name>pear</name>
    </item>
  </items>
  <total_segments>
    <item>
      <code>subtotal</code>
      <title>Subtotal</title>
      <value>6.2</value>
    </item>
    <item>
      <code>shipping</code>
      <title>Shipping &amp;amp; Handling (Flat Rate - Fixed)</title>
      <value>10</value>
    </item>
    <item>
      <code>tax</code>
      <title>Tax</title>
      <value>0</value>
      <extension_attributes>
        <tax_grandtotal_details/>
      </extension_attributes>
    </item>
    <item>
      <code>grand_total</code>
      <title>Grand Total</title>
      <value>16.2</value>
      <area>footer</area>
    </item>
  </total_segments>
</response>

[kassner]

@SerhiyShkolyarenko your own example does not return the discount in total_segments.

[SerhiyShkolyarenko]

That was a service output example. There are lines

  <discount_amount>0</discount_amount>
  <base_discount_amount>0</base_discount_amount>
  <subtotal_with_discount>6.2</subtotal_with_discount>
  <base_subtotal_with_discount>6.2</base_subtotal_with_discount>

which cover your case.
Here is example with discount applied:

<?xml version="1.0"?>
<response>
  <grand_total>29</grand_total>
  <base_grand_total>29</base_grand_total>
  <subtotal>30</subtotal>
  <base_subtotal>30</base_subtotal>
  <discount_amount>-6</discount_amount>
  <base_discount_amount>-6</base_discount_amount>
  <subtotal_with_discount>24</subtotal_with_discount>
  <base_subtotal_with_discount>24</base_subtotal_with_discount>
  <shipping_amount>5</shipping_amount>
  <base_shipping_amount>5</base_shipping_amount>
  <shipping_discount_amount>0</shipping_discount_amount>
  <base_shipping_discount_amount>0</base_shipping_discount_amount>
  <tax_amount>0</tax_amount>
  <base_tax_amount>0</base_tax_amount>
  <weee_tax_applied_amount></weee_tax_applied_amount>
  <shipping_tax_amount>0</shipping_tax_amount>
  <base_shipping_tax_amount>0</base_shipping_tax_amount>
  <subtotal_incl_tax>30</subtotal_incl_tax>
  <base_subtotal_incl_tax>30</base_subtotal_incl_tax>
  <shipping_incl_tax>5</shipping_incl_tax>
  <base_shipping_incl_tax>5</base_shipping_incl_tax>
  <base_currency_code>USD</base_currency_code>
  <quote_currency_code>USD</quote_currency_code>
  <coupon_code>123456</coupon_code>
  <items_qty>1</items_qty>
  <items>
    <item>
      <item_id>1</item_id>
      <price>30</price>
      <base_price>30</base_price>
      <qty>1</qty>
      <row_total>30</row_total>
      <base_row_total>30</base_row_total>
      <row_total_with_discount>0</row_total_with_discount>
      <tax_amount>0</tax_amount>
      <base_tax_amount>0</base_tax_amount>
      <tax_percent>0</tax_percent>
      <discount_amount>6</discount_amount>
      <base_discount_amount>6</base_discount_amount>
      <discount_percent>20</discount_percent>
      <price_incl_tax>30</price_incl_tax>
      <base_price_incl_tax>30</base_price_incl_tax>
      <row_total_incl_tax>30</row_total_incl_tax>
      <base_row_total_incl_tax>30</base_row_total_incl_tax>
      <options>[]</options>
      <weee_tax_applied_amount></weee_tax_applied_amount>
      <weee_tax_applied></weee_tax_applied>
      <name>stepper motor</name>
    </item>
  </items>
  <total_segments>
    <item>
      <code>subtotal</code>
      <title>Subtotal</title>
      <value>30</value>
    </item>
    <item>
      <code>shipping</code>
      <title>Shipping &amp;amp; Handling (Flat Rate - Fixed)</title>
      <value>5</value>
    </item>
    <item>
      <code>discount</code>
      <title>Discount (123456)</title>
      <value>-6</value>
    </item>
    <item>
      <code>tax</code>
      <title>Tax</title>
      <value>0</value>
      <extension_attributes>
        <tax_grandtotal_details/>
      </extension_attributes>
    </item>
    <item>
      <code>grand_total</code>
      <title>Grand Total</title>
      <value>29</value>
      <area>footer</area>
    </item>
  </total_segments>
</response>

Discount in total segments is present there.

[SerhiyShkolyarenko]

Closing the issue as far as we covered different aspects of the topic.