Document variant filtering rule behavior

Add test to conver scenario where we have conficting rules

app/services/product_tag_rules_filterer.rb

@@ -4,6 +4,13 @@
 # Tag rules exists in the context of enterprise, customer, and variant_overrides,
 # and are applied to variant_overrides only. Returns a Spree::Variant AR object.
 
+# The filtering is somewhat not intuitive when they are conflicting rules in play:
+#  * When a variant is hidden by a default rule, the order of customer related rules doesn't matter
+#    ( despite the use of `TagRule::FilterProducts.prioritised` ). It will apply the "show rule"
+#    if any
+#  * When there is no default rule, the order of customer related rules doesn't matter, it will
+#    apply the "hide rule" if any
+#
 class ProductTagRulesFilterer
   def initialize(distributor, customer, variants_relation)
     @distributor = distributor

spec/services/product_tag_rules_filterer_spec.rb

@@ -18,7 +18,7 @@ RSpec.describe ProductTagRulesFilterer do
     }
     let(:customer) { create(:customer, enterprise: distributor) }
     let(:variants_relation) {
-      Spree::Variant.where(supplier: distributor.id)
+      Spree::Variant.left_joins(:variant_overrides).where(supplier: distributor.id)
     }
     let(:default_hide_rule) {
       create(:filter_products_tag_rule,
@@ -50,9 +50,98 @@ RSpec.describe ProductTagRulesFilterer do
     }
     let(:filterer) { described_class.new(distributor, customer, variants_relation) }
 
-    context "when the distributor has no rules" do
-      it "returns the relation unchanged" do
-        expect(filterer.call).to eq variants_relation
+    describe "#call" do
+      before do
+        v1
+        v2
+        v3
+        v4
+      end
+
+      context "when the distributor has no rules" do
+        it "returns the relation unchanged" do
+          expect(filterer.call).to eq variants_relation
+        end
+      end
+
+      context "with hide rule" do
+        it "hides the variant matching the rule" do
+          customer.update_attribute(:tag_list, hide_rule.preferred_customer_tags)
+          variant_hidden_by_rule.update_attribute(:tag_list, hide_rule.preferred_variant_tags)
+
+          expect(filterer.call).not_to include(variant_hidden_by_rule.variant)
+        end
+
+        context "with mutiple conflicting rules" do
+          it "applies the hide rule" do
+            # Customer has show rule tag and hide rule tag
+            customer.update_attribute(:tag_list,
+                                      [hide_rule.preferred_customer_tags,
+                                       show_rule.preferred_customer_tags])
+            # Variant has show rule tag and hide rule tag
+            variant_hidden_by_rule.update_attribute(:tag_list,
+                                                    [hide_rule.preferred_variant_tags,
+                                                     hide_rule.preferred_variant_tags,])
+            hide_rule.update_attribute(:priority, 1)
+            show_rule.update_attribute(:priority, 2)
+
+            expect(filterer.call).not_to include(variant_hidden_by_rule.variant)
+
+            # Re order rule
+            hide_rule.update_attribute(:priority, 2)
+            show_rule.update_attribute(:priority, 1)
+
+            expect(filterer.call).not_to include(variant_hidden_by_rule.variant)
+          end
+        end
+      end
+
+      context "with variant hidden by default" do
+        before do
+          variant_hidden_by_default.update_attribute(:tag_list,
+                                                     default_hide_rule.preferred_variant_tags)
+        end
+
+        it "excludes variant hidden by default" do
+          expect(filterer.call).not_to include(variant_hidden_by_default.variant)
+        end
+
+        context "with variant rule overriding default rule" do
+          it "includes variant hidden by default" do
+            customer.update_attribute(:tag_list, show_rule.preferred_customer_tags)
+            # Variant has default rule tag and show rule tag
+            variant_hidden_by_default.update_attribute(:tag_list,
+                                                       [default_hide_rule.preferred_variant_tags,
+                                                        show_rule.preferred_variant_tags])
+
+            expect(filterer.call).to include(variant_hidden_by_default.variant)
+          end
+
+          context "with mutiple conflicting rules applying to same variant" do
+            it "applies the show rule" do
+              # customer has show rule and hide rule tag
+              customer.update_attribute(:tag_list,
+                                        [show_rule.preferred_customer_tags,
+                                         hide_rule.preferred_customer_tags])
+
+              # Variant has default rule tag and show rule tag and hide rule tag
+              show_rule.update_attribute(:priority, 1)
+              hide_rule.update_attribute(:priority, 2)
+              variant_hidden_by_default.update_attribute(:tag_list,
+                                                         [default_hide_rule.preferred_variant_tags,
+                                                          show_rule.preferred_variant_tags,
+                                                          hide_rule.preferred_variant_tags])
+
+              expect(filterer.call).to include(variant_hidden_by_default.variant)
+
+              # Re order rule
+              show_rule.update_attribute(:priority, 2)
+              hide_rule.update_attribute(:priority, 1)
+
+              expect(filterer.call).to include(variant_hidden_by_default.variant)
+            end
+          end
+        end
       end
     end