Use our namespace for decorator constant

app/decorators/models/alchemy/solidus/spree_product_decorator.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Alchemy
+  module Solidus
+    module SpreeProductDecorator
+      def self.prepended(base)
+        base.include Alchemy::Solidus::TouchAlchemyIngredients
+        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
+end

app/decorators/models/alchemy/solidus/spree_taxon_decorator.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Alchemy
+  module Solidus
+    module SpreeTaxonDecorator
+      def self.prepended(base)
+        base.include Alchemy::Solidus::TouchAlchemyIngredients
+        base.has_many :alchemy_ingredients, class_name: "Alchemy::Ingredients::SpreeTaxon", as: :related_object, dependent: :nullify
+      end
+
+      ::Spree::Taxon.prepend self
+    end
+  end
+end

app/decorators/models/alchemy/solidus/spree_variant_decorator.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Alchemy
+  module Solidus
+    module SpreeVariantDecorator
+      def self.prepended(base)
+        base.include Alchemy::Solidus::TouchAlchemyIngredients
+        base.has_many :alchemy_ingredients, class_name: "Alchemy::Ingredients::SpreeVariant", as: :related_object, dependent: :nullify
+      end
+
+      ::Spree::Variant.prepend self
+    end
+  end
+end

app/models/alchemy/solidus/touch_alchemy_ingredients.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Alchemy
+  module Solidus
+    module TouchAlchemyIngredients
+      extend ActiveSupport::Concern
+
+      included do
+        after_update :touch_alchemy_ingredients
+        after_touch :touch_alchemy_ingredients
+      end
+
+      private
+
+      def touch_alchemy_ingredients
+        alchemy_ingredients.each(&:touch)
+      end
+    end
+  end
+end