_cbor2.CBORDecodeEOF: premature end of stream

[gg0074x]

Describe the bug
When using lists on a Datum and signing the transaction i noticed that the program failed because of a decoding issue with lists of certain length

To Reproduce
My datum class was:

@dataclass
class Datum(PlutusData):
    CONSTR_ID = 1
    data: list[bytes]

And the list contained the bytes for the string "Hello world!" repeated more than 24 times
Signing a transaction with an output with such Datum fails

Logs

Traceback (most recent call last):
  File "/home/arch/send_datum.py", line 33, in <module>
    datum = LargeDatum.from_cbor(utxo.output.datum.cbor)  # ty:ignore[unresolved-attribute]
  File "/home/arch/.venv/lib/python3.14/site-packages/pycardano/serialization.py", line 543, in from_cbor
    value = cbor2.loads(payload)
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 846, in loads
    ).decode()
      ~~~~~~^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 239, in decode
    return self._decode()
           ~~~~~~~~~~~~^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 226, in _decode
    return decoder(self, subtype)
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 473, in decode_semantic
    tag.value = self._decode(unshared=True)
                ~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 226, in _decode
    return decoder(self, subtype)
  File "/home/arch/.venv/lib/python3.14/site-packages/pycardano/serialization.py", line 203, in decode_array
    ret = IndefiniteFrozenList(list(self.decode_array(subtype=subtype)))
                                    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 411, in decode_array
    value = self._decode()
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 226, in _decode
    return decoder(self, subtype)
  File "/home/arch/.venv/lib/python3.14/site-packages/pycardano/serialization.py", line 207, in decode_array
    return self.decode_array(subtype=subtype)
           ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 425, in decode_array
    items.append(self._decode())
                 ~~~~~~~~~~~~^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 226, in _decode
    return decoder(self, subtype)
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 377, in decode_string
    result = self.read(length).decode("utf-8", self._str_errors)
             ~~~~~~~~~^^^^^^^^
  File "/home/arch/.venv/lib/python3.14/site-packages/cbor2pure/_decoder.py", line 204, in read
    raise CBORDecodeEOF(
    ...<2 lines>...
    )
_cbor2.CBORDecodeEOF: premature end of stream (expected to read 12 bytes, got 3 instead)

It appears that serialization.py consumes a byte that is later needed, the problematic cbor had the bytes:

D8 7A                                # tag(122)
   9F                                # array(*)
      98 18                          # array(24)

where the byte 18 was read by serialization.py and then a call to decode_array read an incorrect length and the content was unaligned from there

Environment and software version:

• OS: Linux 6.6.87.2-microsoft-standard-WSL2
• PyCardano Version 0.19.1

Additional context
This bug only happens with cbor2pure and not with the cbor c extension

[cffls]

Thanks @gg0074x for reporting this issue. It is fixed in #479 .