From 153e6f4e07bdaf32d6acf1ef420c5a3acb26cd5f Mon Sep 17 00:00:00 2001
From: Sam Wilson <sam@binarycake.ca>
Date: Fri, 5 Jul 2024 20:20:36 -0400
Subject: [PATCH] Better RLP error message for mismatched element count

---
 src/ethereum/rlp.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/ethereum/rlp.py b/src/ethereum/rlp.py
index 7fcc85335c..3ada0f4fac 100644
--- a/src/ethereum/rlp.py
+++ b/src/ethereum/rlp.py
@@ -261,10 +261,15 @@ def _deserialize_to_dataclass(cls: Type[U], decoded: Simple) -> U:
     target_fields = fields(cls)
 
     if isinstance(decoded, bytes):
-        raise RLPDecodingError
+        raise RLPDecodingError(f"got `bytes` while decoding `{cls.__name__}`")
 
     if len(target_fields) != len(decoded):
-        raise RLPDecodingError
+        name = cls.__name__
+        actual = len(decoded)
+        expected = len(target_fields)
+        raise RLPDecodingError(
+            f"`{name}` needs {expected} field(s), but got {actual} instead"
+        )
 
     values: Dict[str, Any] = {}