bug.py

from typing import Any, Optional, Type

from devtools import debug
from msgspec import Struct
from msgspec.json import Decoder


class uint(int):
    pass


class address(str):
    pass


class hexbytes(bytes):
    pass


def dec_hook(type: Type, obj: Any) -> Any:
    if type is uint:
        return uint(obj, 16)
    if type is hexbytes:
        return hexbytes.fromhex(obj[2:])
    if type is address and obj:
        return address(obj.upper())


renames = {
    "sender": "from",
    "max_fee": "maxFeePerGas",
    "max_priority_fee": "maxPriorityFeePerGas",
}
rename_fn = lambda item: renames.get(item, item)


class TransactionBase(Struct, rename=rename_fn):
    # the `type` field is omitted since it's used in the tagged union
    sender: address
    to: Optional[address] = None  # <-- this works with str but not a subclass of str


class Transaction1559(TransactionBase, tag="0x2"):
    max_fee: uint
    max_priority_fee: uint


Transaction = Transaction1559  # | other types omitted here

samples = [
    b'{"from":"0xbe2cba3fe1b4287226c6f6d9d187891dab00b033","maxPriorityFeePerGas":"0x59682f00","maxFeePerGas":"0x4a817c800","to":"0xcc7c7d5dd10a2573a707cae403b3e40eb20fcd0c","type":"0x2"}',
    b'{"from":"0xac9d54ca08740a608b6c474e5ca07d51ca8117fa","maxPriorityFeePerGas":"0x59682f00","maxFeePerGas":"0x59c3553db","to":null,"type":"0x2"}',
]
for sample in samples:
    tx = Decoder(Transaction, dec_hook=dec_hook).decode(sample)
    debug(tx)