Add variant scoping to availability_validator_decorator by using line_item.scoper and moving Spree::Stock::Quantifier.can_supply? to VariantStock so that it becomes overridable

app/models/concerns/variant_stock.rb

@@ -114,6 +114,17 @@ module VariantStock
     end
   end
 
+  # Moving Spree::Stock::Quantifier.can_supply? to the variant enables us to override this behaviour for variant overrides
+  # We can have this responsibility here in the variant because there is only one stock item per variant
+  #
+  # Here we depend only on variant.total_on_hand and variant.on_demand.
+  #   This way, variant_overrides only need to override variant.total_on_hand and variant.on_demand.
+  def can_supply?(quantity)
+    return true unless Spree::Config[:track_inventory_levels]
+
+    on_demand || total_on_hand >= quantity
+  end
+
   # We can have this responsibility here in the variant because there is only one stock item per variant
   #
   # This enables us to override this behaviour for variant overrides

app/models/spree/line_item_decorator.rb

@@ -125,6 +125,10 @@ Spree::LineItem.class_eval do
     end
   end
 
+  def scoper
+    @scoper ||= OpenFoodNetwork::ScopeVariantToHub.new(order.distributor)
+  end
+
   private
 
   def update_inventory_with_scoping
@@ -133,10 +137,6 @@ Spree::LineItem.class_eval do
   end
   alias_method_chain :update_inventory, :scoping
 
-  def scoper
-    @scoper ||= OpenFoodNetwork::ScopeVariantToHub.new(order.distributor)
-  end
-
   def calculate_final_weight_volume
     if final_weight_volume.present? && quantity_was > 0
       self.final_weight_volume = final_weight_volume * quantity / quantity_was

app/models/spree/stock/availability_validator_decorator.rb

@@ -24,18 +24,26 @@ Spree::Stock::AvailabilityValidator.class_eval do
 
   def line_item_shipment(line_item)
     return line_item.target_shipment if line_item.target_shipment
-    return line_item.order.shipments.first if line_item.order.present? && line_item.order.shipments.any?
+    return line_item.order.shipments.first if line_item.order.andand.shipments.any?
   end
 
-  # This is the spree v2.0.4 implementation of validate
-  # But using the calculated quantity instead of the line_item.quantity.
+  # Overrides Spree v2.0.4 validate method version to:
+  #   - scope variants to hub and thus acivate variant overrides
+  #   - use calculated quantity instead of the line_item.quantity
+  #   - rely on Variant.can_supply? instead of Stock::Quantified.can_supply?
+  #       so that it works correctly for variant overrides
   def validate_quantity(line_item, quantity)
-    quantifier = Spree::Stock::Quantifier.new(line_item.variant_id)
-    return if quantifier.can_supply? quantity
+    line_item.scoper.scope(line_item.variant)
 
+    add_out_of_stock_error(line_item) unless line_item.variant.can_supply? quantity
+  end
+
+  def add_out_of_stock_error(line_item)
     variant = line_item.variant
-    display_name = %Q{#{variant.name}}
-    display_name += %Q{ (#{variant.options_text})} unless variant.options_text.blank?
-    line_item.errors[:quantity] << Spree.t(:out_of_stock, :scope => :order_populator, :item => display_name.inspect)
+    display_name = %{#{variant.name}}
+    display_name += %{(#{variant.options_text})} if variant.options_text.present?
+    line_item.errors[:quantity] << Spree.t(:out_of_stock,
+                                           scope: :order_populator,
+                                           item: display_name.inspect)
   end
 end