Accept 19-digit Visa card numbers

src/validators/card.py

@@ -42,7 +42,7 @@ def card_number(value: str, /):
 
 @validator
 def visa(value: str, /):
-    """Return whether or not given value is a valid Visa card number.
+    """Return whether or not given value is a valid 16- or 19-digit Visa card number.
 
     Examples:
         >>> visa('4242424242424242')
@@ -59,7 +59,7 @@ def visa(value: str, /):
         (ValidationError): If `value` is an invalid Visa card number.
     """
     pattern = re.compile(r"^4")
-    return card_number(value) and len(value) == 16 and pattern.match(value)
+    return card_number(value) and len(value) in (16, 19) and pattern.match(value)
 
 
 @validator

tests/test_card.py

@@ -17,7 +17,7 @@
     visa,
 )
 
-visa_cards = ["4242424242424242", "4000002760003184"]
+visa_cards = ["4242424242424242", "4000002760003184", "4000000000000000006"]
 mastercard_cards = ["5555555555554444", "2223003122003222"]
 amex_cards = ["378282246310005", "371449635398431"]
 unionpay_cards = ["6200000000000005"]
@@ -63,6 +63,22 @@ def test_returns_true_on_valid_visa(value: str):
     assert visa(value)
 
 
+@pytest.mark.parametrize(
+    "value",
+    ["400000000000006", "40000000000000006", "400000000000000002", "40000000000000000002"],
+)
+def test_visa_rejects_unsupported_lengths(value: str):
+    """Reject unsupported lengths even when the checksum and prefix match."""
+    assert card_number(value) is True
+    assert isinstance(visa(value), ValidationError)
+
+
+@pytest.mark.parametrize("value", ["4000000000000000000", "4000000000000000007"])
+def test_visa_rejects_bad_checksum_at_nineteen_digits(value: str):
+    """A supported length must not bypass the Luhn check."""
+    assert isinstance(visa(value), ValidationError)
+
+
 @pytest.mark.parametrize(
     "value",
     mastercard_cards + amex_cards + unionpay_cards + diners_cards + jcb_cards + discover_cards,