Fix crash when validating credit card number

Author: WhyNotHugo

payments/fields.py

@@ -8,6 +8,7 @@
 from django.core import validators
 from django.utils.translation import gettext_lazy as _
 
+from .core import CARD_TYPES
 from .core import get_credit_card_issuer
 from .utils import get_month_choices
 from .utils import get_year_choices
@@ -34,16 +35,17 @@ def to_python(self, value):
             value = re.sub(r"[\s-]+", "", value)
         return super().to_python(value)
 
-    def validate(self, value):
-        card_type, issuer_name = get_credit_card_issuer(value)
+    def validate(self, value) -> None:
+        card_type, _issuer_name = get_credit_card_issuer(value)
         if value in validators.EMPTY_VALUES and self.required:
             raise forms.ValidationError(self.error_messages["required"])
         if value and not self.cart_number_checksum_validation(self, value):
             raise forms.ValidationError(self.error_messages["invalid"])
         if value and self.valid_types is not None and card_type not in self.valid_types:
-            valid_types = map(issuer_name, self.valid_types)
+            card_type_names = {ct: name for _, ct, name in CARD_TYPES}
+            valid_type_names = [card_type_names.get(t, t) for t in self.valid_types]
             error_message = self.error_messages["invalid_type"] % {
-                "valid_types": ", ".join(valid_types)
+                "valid_types": ", ".join(valid_type_names)
             }
             raise forms.ValidationError(error_message)
 

payments/test_fields.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+import pytest
+from django.core.exceptions import ValidationError
+
+from payments.fields import CreditCardNumberField
+
+
+def test_validate_rejects_card_type_not_in_valid_types() -> None:
+    # 4111111111111111 is a valid Visa test number (passes Luhn check)
+    field = CreditCardNumberField(valid_types=["mastercard"])
+    with pytest.raises(ValidationError, match="We accept only MasterCard"):
+        field.validate("4111111111111111")