lnsweep: use lnworker.is_accepted_mpp to decide if we can

release the preimage. (see #9280)

lnworker.is_accepted_mpp includes an assert that will raise
if the MPP has been cleaned-up too early.

electrum/lnsweep.py

@@ -297,7 +297,7 @@ def create_sweeptxs_for_our_ctx(
         ctn=ctn)
     for (direction, htlc), (ctx_output_idx, htlc_relative_idx) in htlc_to_ctx_output_idx_map.items():
         if direction == RECEIVED:
-            if chan.lnworker.is_incomplete_mpp(htlc.payment_hash):
+            if not chan.lnworker.is_accepted_mpp(htlc.payment_hash):
                 # do not redeem this, it might publish the preimage of an incomplete MPP
                 continue
             preimage = chan.lnworker.get_preimage(htlc.payment_hash)
@@ -434,11 +434,13 @@ def create_sweeptxs_for_their_ctx(
     for (direction, htlc), (ctx_output_idx, htlc_relative_idx) in htlc_to_ctx_output_idx_map.items():
         is_received_htlc = direction == RECEIVED
         if not is_received_htlc and not is_revocation:
-            if chan.lnworker.get_payment_status(htlc.payment_hash) == PR_PAID:
-                preimage = chan.lnworker.get_preimage(htlc.payment_hash)
-            else:
+            if not chan.lnworker.is_accepted_mpp(htlc.payment_hash):
                 # do not redeem this, it might publish the preimage of an incomplete MPP
                 continue
+            preimage = chan.lnworker.get_preimage(htlc.payment_hash)
+            if not preimage:
+                # we might not have the preimage if this is a hold invoice
+                continue
         else:
             preimage = None
         create_sweeptx_for_htlc(

electrum/lnworker.py

@@ -2332,10 +2332,11 @@ class LNWallet(LNWorker):
         total = sum([_htlc.amount_msat for scid, _htlc in mpp_status.htlc_set])
         return total >= mpp_status.expected_msat
 
-    def is_incomplete_mpp(self, payment_hash: bytes) -> bool:
+    def is_accepted_mpp(self, payment_hash: bytes) -> bool:
         payment_key = self._get_payment_key(payment_hash)
         status = self.received_mpp_htlcs.get(payment_key.hex())
-        return status and status.resolution == RecvMPPResolution.WAITING
+        assert status is not None
+        return status.resolution == RecvMPPResolution.ACCEPTED
 
     def get_first_timestamp_of_mpp(self, payment_key: bytes) -> int:
         mpp_status = self.received_mpp_htlcs.get(payment_key.hex())