Adds validate_allowed_to_pay(), which validates whether you’re allowed to pay for an invoice

registrasion/controllers/invoice.py

@@ -126,6 +126,30 @@ class InvoiceController(object):
 
         return invoice
 
+    def _refresh(self):
+        ''' Refreshes the underlying invoice and cart objects. '''
+        self.invoice.refresh_from_db()
+        if self.invoice.cart:
+            self.invoice.cart.refresh_from_db()
+
+    def validate_allowed_to_pay(self):
+        ''' Passes cleanly if we're allowed to pay, otherwise raise
+        a ValidationError. '''
+
+        self._refresh()
+
+        if not self.invoice.is_unpaid:
+            raise ValidationError("You can only pay for unpaid invoices.")
+
+        if not self.invoice.cart:
+            return
+
+        if not self._invoice_matches_cart():
+            raise ValidationError("The registration has been amended since "
+                                  "generating this invoice.")
+
+        CartController(self.invoice.cart).validate_cart()
+
     def total_payments(self):
         ''' Returns the total amount paid towards this invoice. '''
 

registrasion/tests/controller_helpers.py

@@ -37,17 +37,8 @@ class TestingInvoiceController(InvoiceController):
     def pay(self, reference, amount):
         ''' Testing method for simulating an invoice paymenht by the given
         amount. '''
-        if self.invoice.cart:
-            cart = CartController(self.invoice.cart)
-            cart.validate_cart()  # Raises ValidationError if invalid
 
-        status = self.invoice.status
-        if status == rego.Invoice.STATUS_VOID:
-            raise ValidationError("Void invoices cannot be paid")
-        elif status == rego.Invoice.STATUS_PAID:
-            raise ValidationError("Paid invoices cannot be paid again")
-        elif status == rego.Invoice.STATUS_REFUNDED:
-            raise ValidationError("Refunded invoices cannot be paid")
+        self.validate_allowed_to_pay()
 
         ''' Adds a payment '''
         payment = rego.ManualPayment.objects.create(

registrasion/tests/test_cart.py

@@ -148,6 +148,10 @@ class RegistrationCartTestCase(SetTimeMixin, TestCase):
         voucher.save()
         return voucher
 
+    @classmethod
+    def reget(cls, object):
+        return type(object).objects.get(id=object.id)
+
 
 class BasicCartTests(RegistrationCartTestCase):
 

registrasion/tests/test_invoice.py

@@ -180,7 +180,7 @@ class InvoiceTestCase(RegistrationCartTestCase):
         invoice_1.void()
 
         with self.assertRaises(ValidationError):
-            invoice_1.pay("Reference", invoice_1.invoice.value)
+            invoice_1.validate_allowed_to_pay()
 
     def test_cannot_void_paid_invoice(self):
         current_cart = TestingCartController.for_user(self.USER_1)
@@ -199,9 +199,22 @@ class InvoiceTestCase(RegistrationCartTestCase):
         with self.assertRaises(ValidationError):
             invoice_1 = TestingInvoiceController.for_cart(current_cart.cart)
 
+    def test_cannot_pay_implicitly_void_invoice(self):
+        cart = TestingCartController.for_user(self.USER_1)
+        cart.add_to_cart(self.PROD_1, 1)
+        invoice = TestingInvoiceController.for_cart(self.reget(cart.cart))
+
+        # Implicitly void the invoice
+        cart.add_to_cart(self.PROD_1, 1)
+
+        with self.assertRaises(ValidationError):
+            invoice.validate_allowed_to_pay()
+
+
+
     # TODO: test partially paid invoice cannot be void until payments
     # are refunded
 
     # TODO: test overpaid invoice results in credit note
 
-    # TODO: test credit note generation more generally 
+    # TODO: test credit note generation more generally