Volume prices only working when Item Total is less than 0

[eddxw]

Volume prices only working when Item Total is less than 0.

In this example the item master price is $20.

Here a discount of $2 should be applied to the order but it isn't.

Now, when the discount is greater than the master price (item total is less than 0) everything works

[eddxw]

I replaced line_item_decorator.rb contents with:

Spree::LineItem.class_eval do
  define_method(:copy_price) do
    self.price = variant.volume_price(quantity, order.user);
  end
end

https://github.com/spree-contrib/spree_volume_pricing/blob/master/app/models/spree/line_item_decorator.rb

Now it's working

But I don't really understand what are these of lines for:

  old_copy_price = instance_method(:copy_price)
  define_method(:copy_price) do
    old_copy_price.bind(self).call
    return unless variant

    if changed? && changes.keys.include?('quantity')
      vprice = variant.volume_price(quantity, order.user)
      if price.present? && vprice <= variant.price
        self.price = vprice and return
      end
    end

    self.price = variant.price if price.nil?
  end

[MatthewKennedy]

Works for me.