lnutil.UpdateAddHtlc: use attrs instead of old-style namedtuple

electrum/lnchannel.py

@@ -32,6 +32,7 @@ import time
 import threading
 
 from aiorpcx import NetAddress
+import attr
 
 from . import ecc
 from . import constants
@@ -434,7 +435,7 @@ class Channel(Logger):
         assert isinstance(htlc, UpdateAddHtlc)
         self._check_can_pay(htlc.amount_msat)
         if htlc.htlc_id is None:
-            htlc = htlc._replace(htlc_id=self.hm.get_next_htlc_id(LOCAL))
+            htlc = attr.evolve(htlc, htlc_id=self.hm.get_next_htlc_id(LOCAL))
         with self.db_lock:
             self.hm.send_htlc(htlc)
         self.logger.info("add_htlc")
@@ -452,7 +453,7 @@ class Channel(Logger):
             htlc = UpdateAddHtlc(**htlc)
         assert isinstance(htlc, UpdateAddHtlc)
         if htlc.htlc_id is None:  # used in unit tests
-            htlc = htlc._replace(htlc_id=self.hm.get_next_htlc_id(REMOTE))
+            htlc = attr.evolve(htlc, htlc_id=self.hm.get_next_htlc_id(REMOTE))
         if 0 <= self.available_to_spend(REMOTE) < htlc.amount_msat:
             raise RemoteMisbehaving('Remote dipped below channel reserve.' +\
                     f' Available at remote: {self.available_to_spend(REMOTE)},' +\

electrum/lnutil.py

@@ -878,21 +878,21 @@ def format_short_channel_id(short_channel_id: Optional[bytes]):
         + 'x' + str(int.from_bytes(short_channel_id[6:], 'big'))
 
 
-class UpdateAddHtlc(namedtuple('UpdateAddHtlc', ['amount_msat', 'payment_hash', 'cltv_expiry', 'htlc_id', 'timestamp'])):
-    # note: typing.NamedTuple cannot be used because we are overriding __new__
-
-    __slots__ = ()
-    def __new__(cls, *args, **kwargs):
-        # if you pass a hex-string as payment_hash, it is decoded to bytes.
-        # Bytes can't be saved to disk, so we save hex-strings.
-        if len(args) > 0:
-            args = list(args)
-            if type(args[1]) is str:
-                args[1] = bfh(args[1])
-            return super().__new__(cls, *args)
-        if type(kwargs['payment_hash']) is str:
-            kwargs['payment_hash'] = bfh(kwargs['payment_hash'])
-        if len(args) < 4 and 'htlc_id' not in kwargs:
-            kwargs['htlc_id'] = None
-        return super().__new__(cls, **kwargs)
+@attr.s(frozen=True)
+class UpdateAddHtlc:
+    amount_msat = attr.ib(type=int, kw_only=True)
+    payment_hash = attr.ib(type=bytes, kw_only=True, converter=hex_to_bytes)
+    cltv_expiry = attr.ib(type=int, kw_only=True)
+    timestamp = attr.ib(type=int, kw_only=True)
+    htlc_id = attr.ib(type=int, kw_only=True, default=None)
 
+    @classmethod
+    def from_tuple(cls, amount_msat, payment_hash, cltv_expiry, htlc_id, timestamp) -> 'UpdateAddHtlc':
+        return cls(amount_msat=amount_msat,
+                   payment_hash=payment_hash,
+                   cltv_expiry=cltv_expiry,
+                   htlc_id=htlc_id,
+                   timestamp=timestamp)
+
+    def to_tuple(self):
+        return (self.amount_msat, self.payment_hash, self.cltv_expiry, self.htlc_id, self.timestamp)

electrum/util.py

@@ -277,6 +277,9 @@ class MyEncoder(json.JSONEncoder):
     def default(self, obj):
         # note: this does not get called for namedtuples :(  https://bugs.python.org/issue30343
         from .transaction import Transaction, TxOutput
+        from .lnutil import UpdateAddHtlc
+        if isinstance(obj, UpdateAddHtlc):
+            return obj.to_tuple()
         if isinstance(obj, Transaction):
             return obj.serialize()
         if isinstance(obj, TxOutput):

electrum/wallet_db.py

@@ -1079,7 +1079,7 @@ class WalletDB(JsonDB):
             # note: for performance, "deserialize=False" so that we will deserialize these on-demand
             v = dict((k, tx_from_any(x, deserialize=False)) for k, x in v.items())
         elif key == 'adds':
-            v = dict((k, UpdateAddHtlc(*x)) for k, x in v.items())
+            v = dict((k, UpdateAddHtlc.from_tuple(*x)) for k, x in v.items())
         elif key == 'fee_updates':
             v = dict((k, FeeUpdate(**x)) for k, x in v.items())
         elif key == 'tx_fees':