Allow cancelling orders that have been fully refunded

core/app/models/spree/order.rb

@@ -852,7 +852,7 @@ def ensure_available_shipping_rates
 
     def after_cancel
       shipments.each(&:cancel!)
-      payments.completed.each(&:cancel!)
+      payments.completed.each { |payment| payment.cancel! unless payment.fully_refunded? }
       payments.store_credits.pending.each(&:void_transaction!)
 
       send_cancel_email

core/app/models/spree/payment.rb

@@ -146,6 +146,11 @@ def can_credit?
       credit_allowed > 0
     end
 
+    # @return [Boolean] true when this payment has been fully refunded
+    def fully_refunded?
+      refunds.map(&:amount).sum == amount
+    end
+
     # @return [Array<String>] the actions available on this payment
     def actions
       sa = source_actions

core/spec/models/spree/order_spec.rb

@@ -43,6 +43,8 @@
   end
 
   describe "#cancel!" do
+    subject { order.cancel! }
+
     context "with captured store credit" do
       let!(:store_credit_payment_method) { create(:store_credit_payment_method) }
       let(:order_total) { 500.00 }
@@ -55,7 +57,20 @@
         order.capture_payments!
       end
 
-      subject { order.cancel! }
+      it "cancels the order" do
+        expect{ subject }.to change{ order.can_cancel? }.from(true).to(false)
+        expect(order).to be_canceled
+      end
+    end
+
+    context "with fully refunded payment" do
+      let(:order) { create(:completed_order_with_totals) }
+      let(:payment_amount) { 50 }
+      let(:payment) { create(:payment, order: order, amount: payment_amount, state: 'completed') }
+
+      before do
+        create(:refund, payment: payment, amount: payment_amount)
+      end
 
       it "cancels the order" do
         expect{ subject }.to change{ order.can_cancel? }.from(true).to(false)

core/spec/models/spree/payment_spec.rb

@@ -630,6 +630,25 @@
     end
   end
 
+  describe "#fully_refunded?" do
+    subject { payment.fully_refunded? }
+
+    before { payment.amount = 100 }
+
+    context 'before refund' do
+      it { is_expected.to be false }
+    end
+
+    context 'when refund total equals payment amount' do
+      before do
+        create(:refund, payment: payment, amount: 50)
+        create(:refund, payment: payment, amount: 50)
+      end
+
+      it { is_expected.to be true }
+    end
+  end
+
   describe "#save" do
     context "captured payments" do
       it "update order payment total" do