Mark shipment as cancelled if all units cancelled

If we cancel all inventory units in a shipment, we should mark it as
cancelled itself because there's nothing to ship.

Co-authored-by: Alistair Norman <alistair@super.gd>
Co-authored-by: Noah Silvera <noah@super.gd>

Author: 3 people

core/app/models/spree/shipment.rb

@@ -207,8 +207,8 @@ def selected_shipping_rate_id=(id)
     # shipped    if already shipped (ie. does not change the state)
     # ready      all other cases
     def determine_state(order)
-      return 'canceled' if order.canceled?
       return 'shipped' if shipped?
+      return 'canceled' if order.canceled? || inventory_units.all?(&:canceled?)
       return 'pending' unless order.can_ship?
       if can_transition_from_pending_to_ready?
         'ready'

core/spec/models/spree/shipment_spec.rb

@@ -50,6 +50,11 @@
       expect(shipment.determine_state(order)).to eq 'canceled'
     end
 
+    it 'returns canceled if all of the inventory units are canceled' do
+      shipment.inventory_units.each(&:cancel!)
+      expect(shipment.determine_state(order)).to eql 'canceled'
+    end
+
     it 'returns pending unless order.can_ship?' do
       allow(order).to receive_messages can_ship?: false
       expect(shipment.determine_state(order)).to eq 'pending'