Raise URNValidationError for truncated URNs

Signed-off-by: Ali Zulfiqar <codewithfourtix@gmail.com>

Author: codewithfourtix

src/commoncode/urn.py

@@ -125,6 +125,9 @@ def decode(urn):
     """
     segments = [unquote_plus(p) for p in urn.split(":")]
 
+    if len(segments) < 3:
+        raise URNValidationError("Invalid URN: missing namespace or object type.")
+
     if not segments[0] == ("urn"):
         raise URNValidationError("Invalid URN prefix. Expected 'urn'.")
 

tests/test_urn.py

@@ -140,3 +140,11 @@ def test_encode_decode_is_idempotent(self):
         encoded = "urn:dje:component:SIP+Servlets+%28MSS%29:v+1.4.0.FINAL"
         assert urn.encode(object_type, **fields) == encoded
         assert urn.decode(encoded) == (object_type, fields)
+
+
+class TruncatedURNTestCase(unittest.TestCase):
+    def test_truncated_urns_raise_validation_error(self):
+        for value in ("", "urn", "urn:", "urn:dje"):
+            with self.subTest(value=value):
+                with self.assertRaises(urn.URNValidationError):
+                    urn.decode(value)