tests: add regression tests for withdraw returning unsigned tx

plugins/txprepare.c

@@ -156,16 +156,28 @@ static struct command_result *signpsbt_done(struct command *cmd,
 	/* Replace with signed tx. */
 	tal_free(utx->tx);
 
-	/* The txid from the final should match our expectation. */
-	psbt_txid(utx, utx->psbt, &txid, &utx->tx);
+	/* The txid from the signed PSBT should match our expectation. */
+	psbt_txid(NULL, utx->psbt, &txid, NULL);
 	if (!bitcoin_txid_eq(&txid, &utx->txid)) {
 		return command_fail(cmd, LIGHTNINGD,
 				    "Signed tx changed txid? Had '%s' now '%s'",
-				    tal_hex(tmpctx,
-					    linearize_wtx(tmpctx, utx->tx)),
-				    fmt_wally_psbt(tmpctx, utx->psbt));
+				    fmt_bitcoin_txid(tmpctx, &utx->txid),
+				    fmt_bitcoin_txid(tmpctx, &txid));
 	}
 
+	/* Finalize the signed PSBT and extract the fully signed tx,
+	 * so that utx->tx contains witness data for the response. */
+	if (!psbt_finalize(utx->psbt))
+		return command_fail(cmd, LIGHTNINGD,
+				    "Signed PSBT not finalizeable: %s",
+				    fmt_wally_psbt(tmpctx, utx->psbt));
+
+	utx->tx = psbt_final_tx(utx, utx->psbt);
+	if (!utx->tx)
+		return command_fail(cmd, LIGHTNINGD,
+				    "Could not extract final tx: %s",
+				    fmt_wally_psbt(tmpctx, utx->psbt));
+
 	req = jsonrpc_request_start(cmd, "sendpsbt",
 				    sendpsbt_done, forward_error,
 				    utx);

tests/test_wallet.py

@@ -2072,6 +2072,77 @@ def test_fundchannel_listtransaction(node_factory, bitcoind):
     assert tx['blockheight'] == 0
 
 
+def test_withdraw_returns_signed_tx(node_factory, bitcoind):
+    """
+    Test that withdraw returns a fully signed transaction in the 'tx' field.
+
+    Regression test for https://github.com/ElementsProject/lightning/issues/8701
+    where withdraw returned an unsigned transaction (empty witnesses) because
+    psbt_txid() used WALLY_PSBT_EXTRACT_NON_FINAL to extract the tx.
+    """
+    l1 = node_factory.get_node(random_hsm=True)
+
+    # Fund the wallet with a few UTXOs
+    addr = l1.rpc.newaddr('p2tr')['p2tr']
+    for i in range(3):
+        l1.bitcoin.rpc.sendtoaddress(addr, 0.01)
+    bitcoind.generate_block(1)
+    wait_for(lambda: len(l1.rpc.listfunds()['outputs']) == 3)
+
+    waddr = l1.bitcoin.rpc.getnewaddress()
+    out = l1.rpc.withdraw(waddr, 'all')
+
+    # The tx field must be a fully signed transaction
+    decoded = bitcoind.rpc.decoderawtransaction(out['tx'])
+
+    # Every segwit input must have witness data (txinwitness)
+    for i, vin in enumerate(decoded['vin']):
+        assert 'txinwitness' in vin, \
+            f"Input {i} has no witness data - tx is unsigned! (issue #8701)"
+        assert len(vin['txinwitness']) > 0, \
+            f"Input {i} has empty witness stack"
+
+    # The returned tx must be directly broadcastable (already sent by withdraw,
+    # but verify it could be re-sent by checking it was accepted)
+    assert decoded['txid'] == out['txid']
+
+
+def test_withdraw_close_output_signed(node_factory, bitcoind):
+    """
+    Test that withdraw correctly signs close outputs (anchor/P2WSH).
+
+    Regression test for https://github.com/ElementsProject/lightning/issues/8701
+    The original issue involved spending channel close outputs (with
+    option_anchors CSV=1) alongside regular wallet UTXOs.
+    """
+    l1, l2 = node_factory.line_graph(2, fundchannel=True, wait_for_announce=True)
+
+    # Close the channel so l1 gets a close output
+    l1.rpc.close(l2.info['id'])
+    bitcoind.generate_block(1, wait_for_mempool=1)
+
+    # Wait for CSV lock (1 block for anchors) and the close output to mature
+    bitcoind.generate_block(100)
+    sync_blockheight(bitcoind, [l1])
+
+    wait_for(lambda: all(o['status'] == 'confirmed' for o in l1.rpc.listfunds()['outputs']))
+
+    # Withdraw all funds - this spends both regular and close outputs
+    waddr = l1.bitcoin.rpc.getnewaddress()
+    out = l1.rpc.withdraw(waddr, 'all')
+
+    decoded = bitcoind.rpc.decoderawtransaction(out['tx'])
+
+    # Every input must have witness data
+    for i, vin in enumerate(decoded['vin']):
+        assert 'txinwitness' in vin, \
+            f"Input {i} has no witness data - tx is unsigned! (issue #8701)"
+        assert len(vin['txinwitness']) > 0, \
+            f"Input {i} has empty witness stack"
+
+    assert decoded['txid'] == out['txid']
+
+
 def test_withdraw_nlocktime(node_factory):
     """
     Test that we don't set the nLockTime to 0 for withdrawal and