fix(billing): reject currency switch while paid subscription is past_due

config/locales/en.yml

@@ -172,6 +172,7 @@ en:
       unsupported_currency: This currency is not supported
       same_currency: This account is already billed in the selected currency
       stripe_customer_not_configured: Stripe customer not configured
+      past_due_subscription: Please settle the outstanding payment before switching currency
       unknown_plan: Could not determine the current plan
       currency_not_available_for_plan: The selected currency is not available for your current plan
       no_payment_method: No payment methods found. Please add a payment method before switching currency.

enterprise/app/services/enterprise/billing/switch_currency_service.rb

@@ -10,6 +10,7 @@ class Enterprise::Billing::SwitchCurrencyService
 
   def perform
     validate!
+    reject_past_due_paid_subscription!
 
     subscriptions = live_subscriptions
     paid_subscription = subscriptions.find { |subscription| !default_price?(subscription) }
@@ -130,10 +131,19 @@ class Enterprise::Billing::SwitchCurrencyService
     )
   end
 
-  # Includes trialing (a prior switch leaves the new sub trialing); excludes past_due so a delinquent account can't switch to restore access unpaid.
+  # Block the switch while a paid sub is past_due, else the account currency/location changes but the unpaid sub stays in the old currency.
+  def reject_past_due_paid_subscription!
+    past_due = all_subscriptions.any? { |subscription| subscription.status == 'past_due' && !default_price?(subscription) }
+    raise Error, I18n.t('errors.billing.past_due_subscription') if past_due
+  end
+
+  def all_subscriptions
+    @all_subscriptions ||= Stripe::Subscription.list(customer: stripe_customer_id, status: 'all', limit: 100).data
+  end
+
+  # Includes trialing (a prior switch leaves the new sub trialing); excludes past_due, which is handled by reject_past_due_paid_subscription!.
   def live_subscriptions
-    Stripe::Subscription.list(customer: stripe_customer_id, status: 'all', limit: 100).data
-                        .select { |subscription| %w[active trialing].include?(subscription.status) }
+    all_subscriptions.select { |subscription| %w[active trialing].include?(subscription.status) }
   end
 
   def validate_payment_method!