Add custom price_for_options method to variant

We need to safely ensure the new price_for_options method in the price
selector will not break for those that have a custom price selector.

If the new method is defined in the price selector class this will
behave normally, and if their customization does not allow for it, we
will instead return an unpersisted Spree::Price from the Spree::Money
object that the deprecated price_for method returns.

Spree::Product can now delegate price_for_options to master variant

core/app/models/spree/product.rb

@@ -85,6 +85,7 @@ def find_or_build_master
              :has_default_price?,
              :images,
              :price_for,
+             :price_for_options,
              :rebuild_vat_prices=,
              to: :find_or_build_master
 

core/app/models/spree/variant.rb

@@ -276,8 +276,9 @@ def price_selector
     end
 
     # Chooses an appropriate price for the given pricing options
+    # This has been deprecated in favor of #price_for_options.
     #
-    # @see Spree::Variant::PriceSelector#price_for
+    # @see Spree::Variant::PriceSelector#price_for_options
     delegate :price_for, to: :price_selector
 
     # Returns the difference in price from the master variant
@@ -293,6 +294,17 @@ def price_same_as_master?(pricing_options = Spree::Config.default_pricing_option
       diff && diff.zero?
     end
 
+    def price_for_options(price_options)
+      if price_selector.respond_to?(:price_for_options)
+        price_selector.price_for_options(price_options)
+      else
+        money = price_for(price_options)
+        return if money.nil?
+
+        Spree::Price.new(amount: money.to_d, variant: self, currency: price_options.currency)
+      end
+    end
+
     # Generates a friendly name and sku string.
     #
     # @return [String]

core/spec/models/spree/variant_spec.rb

@@ -269,6 +269,39 @@
       expect(variant.price_selector).to receive(:price_for).with(price_options)
       variant.price_for(price_options)
     end
+
+    it "returns a Spree::Money object" do
+      expect(variant.price_for(price_options)).to eq Spree::Money.new(19.99)
+    end
+  end
+
+  context "#price_for_options(price_options)" do
+    subject { variant.price_for_options(price_options) }
+
+    let(:price_options) { Spree::Config.variant_price_selector_class.pricing_options_class.new }
+
+    it "delegates to the price_selector" do
+      expect(variant.price_selector).to receive(:price_for_options).with(price_options)
+      subject
+    end
+
+    it "returns a Spree::Price object for the given pricing_options", :aggregate_failures do
+      expect(subject).to be_a Spree::Price
+      expect(subject.amount).to eq 19.99
+    end
+
+    context "when the price_selector does not implement #price_for_options" do
+      before do
+        allow(variant.price_selector).to receive(:respond_to?).with(:price_for_options).and_return false
+      end
+
+      it "returns an unpersisted Spree::Price", :aggregate_failures do
+        expect(Spree::Deprecation).to receive(:warn).
+          with(/^price_for is deprecated and will be removed/, any_args)
+        expect(subject).to be_a Spree::Price
+        expect(subject.amount).to eq 19.99
+      end
+    end
   end
 
   context "#price_difference_from_master" do