Touch taxons individually after product update

The Solidus implementation did not trigger `touch` on taxons, but
updated the `updated_at` timestamp in an `update_all`.

Since we want to invalidate ingredient spree taxons cache as well
we need to use `touch` here and use the `after_touch` callback of
`Spree::Taxon`.

app/decorators/models/spree/spree_product_decorator.rb

@@ -7,6 +7,21 @@ def self.prepended(base)
       base.has_many :alchemy_ingredients, class_name: "Alchemy::Ingredients::SpreeProduct", as: :related_object, dependent: :nullify
     end
 
+    private
+
+    # Overwritten Solidus' default behavior
+    #
+    # The Solidus implementation did not trigger `touch` on taxons, but
+    # updated the `updated_at` timestamp in an `update_all`.
+    #
+    # Since we want to invalidate ingredient spree taxons cache as well
+    # we need to use `touch` here and use the `after_touch` callback of
+    # Spree::Taxon
+    #
+    def touch_taxons
+      taxons.each(&:touch)
+    end
+
     ::Spree::Product.prepend self
   end
 end

spec/models/spree/product_spec.rb

@@ -9,26 +9,40 @@
     let(:page) { create(:alchemy_page) }
     let(:page_version) { create(:alchemy_page_version, page: page) }
     let(:element) { create(:alchemy_element, page_version: page_version) }
-    let!(:ingredient) { Alchemy::Ingredients::SpreeProduct.create!(element: element, role: "product", related_object: product) }
     let(:product) { create(:product) }
 
-    it "invalidates the cache on update" do
-      travel_to 5.minutes.from_now do
-        current_time = Time.current
-        expect { product.reload.update!(name: "New name") }.to change { ingredient.reload.updated_at }.to(current_time)
-        expect(element.reload.updated_at).to eq(current_time)
-        expect(page_version.reload.updated_at).to eq(current_time)
-        expect(page.reload.updated_at).to eq(current_time)
+    context "if assigned to ingredient spree taxon" do
+      let!(:ingredient) { Alchemy::Ingredients::SpreeProduct.create!(element: element, role: "product", related_object: product) }
+
+      it "invalidates the cache on update" do
+        travel_to 5.minutes.from_now do
+          current_time = Time.current
+          expect { product.reload.update!(name: "New name") }.to change { ingredient.reload.updated_at }.to(current_time)
+          expect(element.reload.updated_at).to eq(current_time)
+          expect(page_version.reload.updated_at).to eq(current_time)
+          expect(page.reload.updated_at).to eq(current_time)
+        end
+      end
+
+      it "invalidates the cache on touch" do
+        travel_to 5.minutes.from_now do
+          current_time = Time.current
+          expect { product.reload.touch }.to change { ingredient.reload.updated_at }.to(current_time)
+          expect(element.reload.updated_at).to eq(current_time)
+          expect(page_version.reload.updated_at).to eq(current_time)
+          expect(page.reload.updated_at).to eq(current_time)
+        end
       end
     end
 
-    it "invalidates the cache on touch" do
-      travel_to 5.minutes.from_now do
-        current_time = Time.current
-        expect { product.reload.touch }.to change { ingredient.reload.updated_at }.to(current_time)
-        expect(element.reload.updated_at).to eq(current_time)
-        expect(page_version.reload.updated_at).to eq(current_time)
-        expect(page.reload.updated_at).to eq(current_time)
+    context "if assigned to taxon that is assigned to ingredient spree taxon" do
+      let(:taxon) { create(:taxon) }
+      let(:product) { create(:product, taxons: [taxon]) }
+
+      let!(:ingredient) { Alchemy::Ingredients::SpreeTaxon.create!(element: element, role: "taxon", related_object: taxon) }
+
+      it "touches ingredient spree taxons elements" do
+        expect { product.reload.touch }.to change { element.reload.updated_at }
       end
     end
   end