Order taxon condition: Allow non-persisted line items

This will lead to an n+1-query if the line items are loaded without
their product classifications. Also I'm not super-sure about the
semantics of the `all` match policy: Do we want to make sure that all
taxons are present in the order, or do we want to make sure that all
line items match any of the taxons?

Author: mamhoff

promotions/app/models/solidus_promotions/conditions/order_taxon.rb

@@ -12,27 +12,34 @@ class OrderTaxon < Condition
       preference :match_policy, :string, default: MATCH_POLICIES.first
 
       def order_eligible?(order, _options = {})
-        order_taxons = taxons_in_order(order)
+        line_item_taxons_ids = taxon_ids_in_order(order)
+        condition_taxon_ids = condition_taxon_ids_with_children
 
         case preferred_match_policy
         when "all"
-          matches_all = taxons.all? do |condition_taxon|
-            order_taxons.where(id: condition_taxon.self_and_descendants.ids).exists?
+          unless line_item_taxons_ids.all? do |line_item_taxon_ids|
+            (line_item_taxon_ids & condition_taxon_ids).any?
           end
 
-          unless matches_all
             eligibility_errors.add(:base, eligibility_error_message(:missing_taxon), error_code: :missing_taxon)
           end
         when "any"
-          unless order_taxons.where(id: condition_taxon_ids_with_children).exists?
+          if line_item_taxons_ids.none? do |line_item_taxon_ids|
+               (line_item_taxon_ids & condition_taxon_ids).any?
+             end
+
             eligibility_errors.add(
               :base,
               eligibility_error_message(:no_matching_taxons),
               error_code: :no_matching_taxons
             )
           end
         when "none"
-          if order_taxons.where(id: condition_taxon_ids_with_children).exists?
+          matches_none = line_item_taxons_ids.none? do |line_item_taxon_ids|
+            (line_item_taxon_ids & condition_taxon_ids).any?
+          end
+
+          unless matches_none
             eligibility_errors.add(
               :base,
               eligibility_error_message(:has_excluded_taxon),
@@ -50,12 +57,11 @@ def to_partial_path
 
       private
 
-      # All taxons in an order
-      def taxons_in_order(order)
-        Spree::Taxon
-          .joins(products: { variants_including_master: :line_items })
-          .where(spree_line_items: { order_id: order.id })
-          .distinct
+      # All taxon IDs in an order
+      def taxon_ids_in_order(order)
+        order.line_items.map do |line_item|
+          line_item.variant.product.classifications.map(&:taxon_id)
+        end
       end
     end
   end

promotions/spec/models/solidus_promotions/conditions/order_taxon_spec.rb

@@ -8,13 +8,17 @@
   let(:condition) do
     described_class.create!(benefit: promotion_benefit)
   end
-  let(:product) { order.products.first }
-  let(:order) { create :order_with_line_items }
+  let(:product) { create(:product) }
+  let(:order) { create :order }
   let(:taxon_one) { create :taxon, name: "first" }
   let(:taxon_two) { create :taxon, name: "second" }
 
   it_behaves_like "a taxon condition"
 
+  before do
+    order.line_items.new(quantity: 1, variant: product.master)
+  end
+
   it { is_expected.to be_updateable }
 
   describe "#eligible?(order)" do
@@ -66,7 +70,7 @@
 
       it "is eligible order has all prefered taxons" do
         product.taxons << taxon_two
-        order.products.last.taxons << taxon_one
+        product.taxons << taxon_one
 
         condition.taxons = [taxon_one, taxon_two]
 
@@ -121,7 +125,7 @@
 
       context "one of the order's products is in a listed taxon" do
         before do
-          order.products.first.taxons << taxon_one
+          product.taxons << taxon_one
           condition.taxons << taxon_one
         end