lnsweep: rm one usage of Transaction.get_preimage_script()

get_preimage_script should really have been private API...
looks like everywhere it is used outside of transaction.py, it is actually abused :/
Other existing usages in plugin code I don't dare to touch without lots of manual testing...

electrum/lnsweep.py

@@ -458,7 +458,7 @@ def create_htlctx_that_spends_from_our_ctx(
     assert (htlc_direction == RECEIVED) == bool(preimage), 'preimage is required iff htlc is received'
     preimage = preimage or b''
     ctn = extract_ctn_from_tx_and_chan(ctx, chan)
-    witness_script, htlc_tx = make_htlc_tx_with_open_channel(
+    witness_script_out, htlc_tx = make_htlc_tx_with_open_channel(
         chan=chan,
         pcp=our_pcp,
         subject=LOCAL,
@@ -471,9 +471,10 @@ def create_htlctx_that_spends_from_our_ctx(
     remote_htlc_sig = chan.get_remote_htlc_sig_for_htlc(htlc_relative_idx=htlc_relative_idx)
     local_htlc_sig = htlc_tx.sign_txin(0, local_htlc_privkey)
     txin = htlc_tx.inputs()[0]
-    witness_program = Transaction.get_preimage_script(txin)
-    txin.witness = make_htlc_tx_witness(remote_htlc_sig, local_htlc_sig, preimage, witness_program)
-    return witness_script, htlc_tx
+    witness_script_in = txin.witness_script
+    assert witness_script_in
+    txin.witness = make_htlc_tx_witness(remote_htlc_sig, local_htlc_sig, preimage, witness_script_in)
+    return witness_script_out, htlc_tx
 
 
 def create_sweeptx_their_ctx_htlc(

electrum/lnutil.py

@@ -620,14 +620,14 @@ def make_htlc_tx_witness(remotehtlcsig: bytes, localhtlcsig: bytes,
     return construct_witness([0, remotehtlcsig, localhtlcsig, payment_preimage, witness_script])
 
 def make_htlc_tx_inputs(htlc_output_txid: str, htlc_output_index: int,
-                        amount_msat: int, witness_script: str) -> List[PartialTxInput]:
+                        amount_msat: int, witness_script: bytes) -> List[PartialTxInput]:
     assert type(htlc_output_txid) is str
     assert type(htlc_output_index) is int
     assert type(amount_msat) is int
-    assert type(witness_script) is str
+    assert type(witness_script) is bytes
     txin = PartialTxInput(prevout=TxOutpoint(txid=bfh(htlc_output_txid), out_idx=htlc_output_index),
                           nsequence=0)
-    txin.witness_script = bfh(witness_script)
+    txin.witness_script = witness_script
     txin.script_sig = b''
     txin._trusted_value_sats = amount_msat // 1000
     c_inputs = [txin]
@@ -826,13 +826,15 @@ def possible_output_idxs_of_htlc_in_ctx(*, chan: 'Channel', pcp: bytes, subject:
     other_revocation_pubkey = derive_blinded_pubkey(other_conf.revocation_basepoint.pubkey, pcp)
     other_htlc_pubkey = derive_pubkey(other_conf.htlc_basepoint.pubkey, pcp)
     htlc_pubkey = derive_pubkey(conf.htlc_basepoint.pubkey, pcp)
-    preimage_script = make_htlc_output_witness_script(is_received_htlc=htlc_direction == RECEIVED,
-                                                      remote_revocation_pubkey=other_revocation_pubkey,
-                                                      remote_htlc_pubkey=other_htlc_pubkey,
-                                                      local_htlc_pubkey=htlc_pubkey,
-                                                      payment_hash=payment_hash,
-                                                      cltv_abs=cltv_abs)
-    htlc_address = redeem_script_to_address('p2wsh', preimage_script)
+    witness_script = make_htlc_output_witness_script(
+        is_received_htlc=htlc_direction == RECEIVED,
+        remote_revocation_pubkey=other_revocation_pubkey,
+        remote_htlc_pubkey=other_htlc_pubkey,
+        local_htlc_pubkey=htlc_pubkey,
+        payment_hash=payment_hash,
+        cltv_abs=cltv_abs,
+    )
+    htlc_address = redeem_script_to_address('p2wsh', witness_script)
     candidates = ctx.get_output_idxs_from_address(htlc_address)
     return {output_idx for output_idx in candidates
             if ctx.outputs()[output_idx].value == htlc.amount_msat // 1000}
@@ -889,16 +891,18 @@ def make_htlc_tx_with_open_channel(*, chan: 'Channel', pcp: bytes, subject: 'HTL
         local_delayedpubkey=delayedpubkey,
         success = is_htlc_success,
         to_self_delay = other_conf.to_self_delay)
-    preimage_script = make_htlc_output_witness_script(is_received_htlc=is_htlc_success,
-                                                      remote_revocation_pubkey=other_revocation_pubkey,
-                                                      remote_htlc_pubkey=other_htlc_pubkey,
-                                                      local_htlc_pubkey=htlc_pubkey,
-                                                      payment_hash=payment_hash,
-                                                      cltv_abs=cltv_abs)
+    witness_script_in = make_htlc_output_witness_script(
+        is_received_htlc=is_htlc_success,
+        remote_revocation_pubkey=other_revocation_pubkey,
+        remote_htlc_pubkey=other_htlc_pubkey,
+        local_htlc_pubkey=htlc_pubkey,
+        payment_hash=payment_hash,
+        cltv_abs=cltv_abs,
+    )
     htlc_tx_inputs = make_htlc_tx_inputs(
         commit.txid(), ctx_output_idx,
         amount_msat=amount_msat,
-        witness_script=preimage_script.hex())
+        witness_script=witness_script_in)
     if is_htlc_success:
         cltv_abs = 0
     htlc_tx = make_htlc_tx(cltv_abs=cltv_abs, inputs=htlc_tx_inputs, output=htlc_tx_output)

tests/test_lnutil.py

@@ -584,7 +584,7 @@ class TestLNUtil(ElectrumTestCase):
             htlc_output_txid=our_commit_tx.txid(),
             htlc_output_index=htlc_output_index,
             amount_msat=amount_msat,
-            witness_script=htlc.hex())
+            witness_script=htlc)
         our_htlc_tx = make_htlc_tx(
             cltv_abs=cltv_abs,
             inputs=our_htlc_tx_inputs,