txprepare: don't crash if we are passed unconfirmed utxos

Changelog-added: `txprepare` doesn't crash lightningd anymore if you pass unconfirmed utxos

common/wallet_tx.c

@@ -205,7 +205,7 @@ struct command_result *wtx_from_utxos(struct wallet_tx *tx,
 	/* + segwit marker + flag */
 	weight = 4 * (4 + 1 + 1 + 4) + 4 * (8 + 1 + out_len) + 1 + 1;
 	for (size_t i = 0; i < tal_count(utxos); i++) {
-		if (!*utxos[i]->blockheight || *utxos[i]->blockheight > maxheight) {
+		if (!utxos[i]->blockheight || *utxos[i]->blockheight > maxheight) {
 			tal_arr_remove(&utxos, i);
 			continue;
 		}
@@ -236,7 +236,9 @@ struct command_result *wtx_from_utxos(struct wallet_tx *tx,
 		tx->amount = total_amount;
 		if (!amount_sat_sub(&tx->amount, tx->amount, fee_estimate))
 			return command_fail(tx->cmd, FUND_CANNOT_AFFORD,
-								"Cannot afford transaction with %s sats of fees",
+					    "Cannot afford transaction with %s"
+					    " sats of fees, make sure to use "
+					    "confirmed utxos.",
 					    type_to_string(tmpctx, struct amount_sat,
 							   &fee_estimate));
 	} else {
@@ -246,7 +248,9 @@ struct command_result *wtx_from_utxos(struct wallet_tx *tx,
 			fee_estimate = amount_tx_fee(fee_rate_per_kw, weight);
 			if (!amount_sat_sub(&tx->change, tx->change, fee_estimate))
 				return command_fail(tx->cmd, FUND_CANNOT_AFFORD,
-						    "Cannot afford transaction with %s sats of fees",
+						    "Cannot afford transaction with %s"
+						    " sats of fees, make sure to use "
+						    "confirmed utxos.",
 						    type_to_string(tmpctx, struct amount_sat,
 								   &fee_estimate));
 			tx->change = AMOUNT_SAT(0);

tests/test_wallet.py

@@ -280,7 +280,6 @@ def test_txprepare_multi(node_factory, bitcoind):
     l1.rpc.txdiscard(prep['txid'])
 
 
-@pytest.mark.xfail(strict=True)
 def test_txprepare(node_factory, bitcoind, chainparams):
     amount = 1000000
     l1 = node_factory.get_node(random_hsm=True)
@@ -374,8 +373,11 @@ def test_txprepare(node_factory, bitcoind, chainparams):
 
     # Try passing unconfirmed utxos
     unconfirmed_utxo = l1.rpc.withdraw(l1.rpc.newaddr()["bech32"], 10**5)
-    utxos = [unconfirmed_utxo["txid"] + ":0"]
-    l1.rpc.txprepare([{addr: Millisatoshi(amount * 3.5 * 1000)}], utxos=utxos)
+    uutxos = [unconfirmed_utxo["txid"] + ":0"]
+    with pytest.raises(RpcError, match=r"Cannot afford transaction .* use "
+                       "confirmed utxos."):
+        l1.rpc.txprepare([{addr: Millisatoshi(amount * 3.5 * 1000)}],
+                         utxos=uutxos)
 
     decode = bitcoind.rpc.decoderawtransaction(prep5['unsigned_tx'])
     assert decode['txid'] == prep5['txid']