Adds fix_simple_errors to cart - it zeroes out unavailable products. Adds test that it does that.

registrasion/controllers/cart.py

@@ -210,7 +210,6 @@ class CartController(object):
         # TODO: validate vouchers
 
         items = rego.ProductItem.objects.filter(cart=cart)
-
         products = set(i.product for i in items)
         available = set(ProductController.available_products(
             user,
@@ -251,6 +250,28 @@ class CartController(object):
         if errors:
             raise ValidationError(errors)
 
+    def fix_simple_errors(self):
+        ''' This attempts to fix the easy errors raised by ValidationError.
+        This includes removing items from the cart that are no longer
+        available, recalculating all of the discounts, and removing voucher
+        codes that are no longer available. '''
+
+        # TODO: fix vouchers first (this affects available discounts)
+
+        # Fix products and discounts
+        items = rego.ProductItem.objects.filter(cart=self.cart)
+        products = set(i.product for i in items)
+        available = set(ProductController.available_products(
+            self.cart.user,
+            products=products,
+        ))
+
+        not_available = products - available
+        zeros = [(product, 0) for product in not_available]
+
+        self.set_quantities(zeros)
+
+
     @transaction.atomic
     def recalculate_discounts(self):
         ''' Calculates all of the discounts available for this product.

registrasion/tests/test_enabling_condition.py

@@ -309,3 +309,32 @@ class EnablingConditionTestCases(RegistrationCartTestCase):
         # Should fail
         with self.assertRaises(ValidationError):
             cart.validate_cart()
+
+    def test_fix_simple_errors_resolves_unavailable_products(self):
+        self.test_validate_cart_when_enabling_conditions_become_unmet()
+        cart = TestingCartController.for_user(self.USER_1)
+
+        # Should just remove all of the unavailable products
+        cart.fix_simple_errors()
+        # Should now succeed
+        cart.validate_cart()
+
+        # Should keep PROD_2 in the cart
+        items = rego.ProductItem.objects.filter(cart=cart.cart)
+        self.assertFalse([i for i in items if i.product == self.PROD_1])
+
+    def test_fix_simple_errors_does_not_remove_limited_items(self):
+        cart = TestingCartController.for_user(self.USER_1)
+
+        cart.add_to_cart(self.PROD_2, 1)
+        cart.add_to_cart(self.PROD_1, 10)
+
+        # Should just remove all of the unavailable products
+        cart.fix_simple_errors()
+        # Should now succeed
+        cart.validate_cart()
+
+        # Should keep PROD_2 in the cart
+        # and also PROD_1, which is now exhausted for user.
+        items = rego.ProductItem.objects.filter(cart=cart.cart)
+        self.assertTrue([i for i in items if i.product == self.PROD_1])