Fix AddPaymentSourcesToWallet changing default when reused

PR solidusio#2913 [1] changed how the new default WalletPaymentSource was set.
Before:
- using the last one found/created by the Order's PaymentSources

After:
- using the user's last WalletPaymentSource.

This is problematic when an order uses a default WalletPaymentSource
but it's not the most recent one.

Fixes issue solidusio#4004 [2]

Now, #make_default uses WalletPaymentSources found or created by the
order, which means it will keep the default payment source if used.

[1] solidusio#2913
[2] solidusio#4004

core/app/models/spree/wallet/add_payment_sources_to_wallet.rb

@@ -24,19 +24,19 @@ def add_to_wallet
       # add valid sources to wallet and optionally set a default
       if sources.any?
         # arbitrarily sort by id for picking a default
-        sources.sort_by(&:id).each do |source|
+        order_wallet_payment_sources = sources.sort_by(&:id).map do |source|
           order.user.wallet.add(source)
         end
 
-        make_default
+        make_default(order_wallet_payment_sources)
       end
     end
   end
 
   protected
 
-  def make_default
-    order.user.wallet.default_wallet_payment_source = order.user.wallet_payment_sources.last
+  def make_default(sources)
+    order.user.wallet.default_wallet_payment_source = sources.last
   end
 
   private

core/spec/models/spree/wallet/add_payment_sources_to_wallet_spec.rb

@@ -4,14 +4,41 @@
 
 RSpec.describe Spree::Wallet::AddPaymentSourcesToWallet, type: :model do
   let(:order) { create(:order_ready_to_complete) }
+  let(:user) { order.user }
 
   describe '#add_to_wallet' do
     subject { described_class.new(order) }
 
+    before do
+      # Ensure the payment is reusable, otherwise false positives occur
+      allow_any_instance_of(Spree::CreditCard).to receive(:reusable?).and_return(true)
+    end
+
     it 'saves the payment source' do
       expect { subject.add_to_wallet }.to change {
         order.user.wallet.wallet_payment_sources.count
       }.by(1)
     end
+
+    context "when the default wallet payment source is used and a more recent wallet payment exists" do
+      before do
+        credit_card_one = user.wallet.add(create(:credit_card, user: user))
+        user.wallet.add(create(:credit_card, user: user))
+        user.wallet.default_wallet_payment_source = credit_card_one # must be the first created card
+        order.payments.first.update!(source: credit_card_one.payment_source)
+      end
+
+      it 'does not make a new wallet payment source' do
+        expect { subject.add_to_wallet }.to_not change {
+          order.user.wallet.wallet_payment_sources.count
+        }
+      end
+
+      it 'does not change the default wallet payment source' do
+        expect { subject.add_to_wallet }.to_not change {
+          user.wallet.default_wallet_payment_source
+        }
+      end
+    end
   end
 end