Allow fulfilling all items of a ready shipment from another location

Prior to this commit, this would not work because the destruction
of the original shipment would result in an exception being thrown.

Ready shipments can be edited and thus have to be able to be destroyed, too.

Fixes #1684

backend/spec/features/admin/orders/shipments_spec.rb

@@ -79,5 +79,26 @@ def ship_shipment
       expect(page).to have_css("#shipment_#{shipment2.id} tr.stock-item", count: 2)
       expect(page).to have_css("#shipment_#{shipment1.id} tr.stock-item", count: 3)
     end
+
+    context "with a ready-to-ship order" do
+      let(:variant) { create(:variant) }
+      let!(:order) do
+        create(
+          :order_ready_to_ship,
+          number: "R100",
+          line_items_attributes: [{ variant: variant, quantity: 5 }]
+        )
+      end
+
+      it "can transfer all items to a new location" do
+        expect(order.shipments.count).to eq(1)
+
+        within_row(1) { click_icon 'arrows-h' }
+        complete_split_to('LA', quantity: 5)
+
+        expect(page).to_not have_content("package from 'NY Warehouse'")
+        expect(page).to have_content("package from 'LA'")
+      end
+    end
   end
 end

core/app/models/spree/inventory_unit.rb

@@ -141,7 +141,7 @@ def ensure_can_destroy
         throw :abort
       end
 
-      unless shipment.pending?
+      if shipment.shipped? || shipment.canceled?
         errors.add(:base, :cannot_destroy_shipment_state, state: shipment.state)
         throw :abort
       end

core/app/models/spree/shipment.rb

@@ -391,7 +391,7 @@ def set_cost_zero_when_nil
     end
 
     def ensure_can_destroy
-      unless pending?
+      if shipped? || canceled?
         errors.add(:state, :cannot_destroy, state: state)
         throw :abort
       end

core/spec/models/spree/inventory_unit_spec.rb

@@ -289,11 +289,10 @@
       expect { inventory_unit.reload }.not_to raise_error
     end
 
-    it "cannot be destroyed if its shipment is ready" do
+    it "can be destroyed if its shipment is ready" do
       inventory_unit = create(:order_ready_to_ship).inventory_units.first
-      expect(inventory_unit.destroy).to eq false
-      expect(inventory_unit.errors.full_messages.join).to match /Cannot destroy/
-      expect { inventory_unit.reload }.not_to raise_error
+      expect(inventory_unit.destroy).to be_truthy
+      expect { inventory_unit.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
 
     it "cannot be destroyed if its shipment is shipped" do

core/spec/models/spree/shipment_spec.rb

@@ -724,11 +724,10 @@
       expect { shipment.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
 
-    it "cannot be destroyed when ready" do
+    it "can be destroyed when ready" do
       shipment = create(:shipment, state: "ready")
-      expect(shipment.destroy).to eq false
-      expect(shipment.errors.full_messages.join).to match /Cannot destroy/
-      expect { shipment.reload }.not_to raise_error
+      expect(shipment.destroy).to be_truthy
+      expect { shipment.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
 
     it "cannot be destroyed when shipped" do