Use real currency for Taler payments unless using demo backend.

app/models/spree/payment_method/taler.rb

@@ -18,6 +18,9 @@ module Spree
     # - backend_url: https://backend.demo.taler.net/instances/sandbox
     # - api_key: sandbox
     class Taler < PaymentMethod
+      # Demo backend instances will use the KUDOS currency.
+      DEMO_PREFIX = "https://backend.demo.taler.net/instances"
+
       preference :backend_url, :string
       preference :api_key, :password
 
@@ -96,7 +99,7 @@ module Spree
       def create_taler_order(payment)
         # We are ignoring currency for now so that we can test with the
         # current demo backend only working with the KUDOS currency.
-        taler_amount = "KUDOS:#{payment.amount}"
+        taler_amount = "#{currency(payment)}:#{payment.amount}"
         urls = Rails.application.routes.url_helpers
         fulfillment_url = urls.payment_gateways_confirm_taler_url(payment_id: payment.id)
         taler_order.create(
@@ -113,6 +116,12 @@ module Spree
           id:,
         )
       end
+
+      def currency(payment)
+        return "KUDOS" if preferred_backend_url.starts_with?(DEMO_PREFIX)
+
+        payment.order.currency
+      end
     end
   end
 end

spec/models/spree/payment_method/taler_spec.rb

@@ -12,8 +12,8 @@ RSpec.describe Spree::PaymentMethod::Taler do
   let(:backend_url) { "https://backend.demo.taler.net/instances/sandbox" }
   let(:token_url) { "#{backend_url}/private/token" }
 
-  describe "#external_payment_url", vcr: true do
-    it "creates an order reference and retrieves a URL to pay at" do
+  describe "#external_payment_url" do
+    it "creates an order reference and retrieves a URL to pay at", vcr: true do
       order = create(:order_ready_for_confirmation, payment_method: taler)
 
       url = subject.external_payment_url(order:)
@@ -23,6 +23,26 @@ RSpec.describe Spree::PaymentMethod::Taler do
       payment = order.payments.last.reload
       expect(payment.response_code).to match "20...[0-9A-Z-]{17}$"
     end
+
+    it "creates the Taler order with the right currency" do
+      order = create(:order_ready_for_confirmation, payment_method: taler)
+
+      backend_url = "https://taler.example.com"
+      token_url = "https://taler.example.com/private/token"
+      order_url = "https://taler.example.com/private/orders"
+      taler = Spree::PaymentMethod::Taler.new(
+        preferred_backend_url: "https://taler.example.com",
+        preferred_api_key: "sandbox",
+      )
+
+      stub_request(:post, token_url).to_return(body: { token: "1234" }.to_json)
+      stub_request(:post, order_url)
+        .with(body: /"amount":"AUD:10.0"/)
+        .to_return(body: { order_id: "one" }.to_json)
+
+      url = taler.external_payment_url(order:)
+      expect(url).to eq "#{backend_url}/orders/one"
+    end
   end
 
   describe "#purchase" do

spec/system/consumer/checkout/payment_spec.rb

@@ -370,6 +370,7 @@ RSpec.describe "As a consumer, I want to checkout my order" do
               Spree::PaymentMethod::Taler.create!(
                 name: "Taler",
                 environment: "test",
+                preferred_backend_url: "https://taler.example.com/",
                 distributors: [distributor]
               )
             end