Do not update finalized fee adjustments

app/models/spree/order_decorator.rb

@@ -144,6 +144,8 @@ Spree::Order.class_eval do
   end
 
   # After changing line items of a completed order
+  # TODO: perhaps this should be triggered from a controller
+  # rather than an after_save callback?
   def update_shipping_fees!
     shipments.each do |shipment|
       next if shipment.shipped?
@@ -153,6 +155,8 @@ Spree::Order.class_eval do
   end
 
   # After changing line items of a completed order
+  # TODO: perhaps this should be triggered from a controller
+  # rather than an after_save callback?
   def update_payment_fees!
     payments.each do |payment|
       next if payment.completed?
@@ -367,6 +371,7 @@ Spree::Order.class_eval do
   end
 
   def update_adjustment!(adjustment)
+    return if adjustment.finalized?
     state = adjustment.state
     adjustment.state = 'open'
     adjustment.update!(self)

spec/models/spree/order_spec.rb

@@ -687,6 +687,26 @@ describe Spree::Order do
         expect(order.adjustment_total).to eq expected_fees - shipping_fee - payment_fee
         expect(order.shipment.adjustment.included_tax).to eq 0.6
       end
+
+      context "when finalized fee adjustments exist on the order" do
+        let(:payment_fee_adjustment) { order.adjustments.payment_fee.first }
+        let(:shipping_fee_adjustment) { order.adjustments.shipping.first }
+
+        before do
+          payment_fee_adjustment.finalize!
+          shipping_fee_adjustment.finalize!
+          order.reload
+        end
+
+        it "does not attempt to update such adjustments" do
+          order.update_attributes(line_items_attributes: [{id: order.line_items.first.id, quantity: 0}])
+
+          # Check if fees got updated
+          order.reload
+          expect(order.adjustment_total).to eq expected_fees
+          expect(order.shipment.adjustment.included_tax).to eq 1.2
+        end
+      end
     end
 
     context "changing the shipping method to one without fees" do