Cannot deserialize PlutusV2 script attached to transaction

[nielstron]

Describe the bug
Trying to deserialize a transaction from cborhex that was generated and hexlified by PyCardano before, I get the following error

Jun 07 23:45:25 ********[12055]: pycardano.exception.DeserializeException: Cannot deserialize object:
Jun 07 23:45:25 ********[12055]: [b'Y,\x1e\x01\x00\x002222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222>
Jun 07 23:45:25 *********[12055]:  in any valid type from (typing.List[pycardano.plutus.PlutusV2Script], <class 'NoneType'>).

To Reproduce
Serialize a Tx with a PlutusV2 script attached, then deserialize again.

Logs
Logs are above

Expected behavior
Transaction.from_cbor(tx.to_cbor()) should work without problems

Environment and software version (please complete the following information):

• OS: Ubuntu 22
• PyCardano Version: latest

Additional context
None

[MartinSchere]

Happening for me too with PlutusV1 scripts

[cffls]

Does the issue still persist in the latest main branch?

[theeldermillenial]

Yes, I can also confirm this is still a problem. It appears as though it's trying to interpret it as a list of bytes rather than just bytes. If you instantiate the Plutus script class with the bytes that throw the error, it instantiates properly.

[theeldermillenial]

I think I figured it out. For types that are just wrappers around Python raw data types, there is no attempt to instantiate them. I ran into this issue when implementing ByteString. We should maybe add in a more generic attempt to cast bytes to their wrapper class.

I'll take a stab at this today.

pycardano/pycardano/serialization.py

Lines 509 to 570 in d1ec439

	def _restore_typed_primitive(
	t: typing.Type, v: Primitive
	) -> Union[Primitive, CBORSerializable]:
	"""Try to restore a value back to its original type based on information given in field.
	Args:
	f (type): A type
	v (:const:`Primitive`): A CBOR primitive.
	Returns:
	Union[:const:`Primitive`, CBORSerializable]: A CBOR primitive or a CBORSerializable.
	"""
	if t is Any or (t in PRIMITIVE_TYPES and isinstance(v, t)):
	return v
	elif isclass(t) and issubclass(t, CBORSerializable):
	return t.from_primitive(v)
	elif hasattr(t, "__origin__") and (t.__origin__ is list):
	t_args = t.__args__
	if len(t_args) != 1:
	raise DeserializeException(
	f"List types need exactly one type argument, but got {t_args}"
	)
	t = t_args[0]
	if not isinstance(v, list):
	raise DeserializeException(f"Expected type list but got {type(v)}")
	return IndefiniteList([_restore_typed_primitive(t, w) for w in v])
	elif isclass(t) and t == ByteString:
	if not isinstance(v, bytes):
	raise DeserializeException(f"Expected type bytes but got {type(v)}")
	return ByteString(v)
	elif isclass(t) and issubclass(t, IndefiniteList):
	try:
	return IndefiniteList(v)
	except TypeError:
	raise DeserializeException(f"Can not initialize IndefiniteList from {v}")
	elif hasattr(t, "__origin__") and (t.__origin__ is dict):
	t_args = t.__args__
	if len(t_args) != 2:
	raise DeserializeException(
	f"Dict types need exactly two type arguments, but got {t_args}"
	)
	key_t = t_args[0]
	val_t = t_args[1]
	if not isinstance(v, dict):
	raise DeserializeException(f"Expected dict type but got {type(v)}")
	return {
	_restore_typed_primitive(key_t, key): _restore_typed_primitive(val_t, val)
	for key, val in v.items()
	}
	elif hasattr(t, "__origin__") and (
	t.__origin__ is Union or t.__origin__ is Optional
	):
	t_args = t.__args__
	for t in t_args:
	try:
	return _restore_typed_primitive(t, v)
	except DeserializeException:
	pass
	raise DeserializeException(
	f"Cannot deserialize object: \n{v}\n in any valid type from {t_args}."
	)
	raise DeserializeException(f"Cannot deserialize object: \n{v}\n to type {t}.")