wallet: implement dev-finalizepsbt for testing feerates.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Author: rustyrussell

wallet/walletrpc.c

@@ -998,6 +998,42 @@ static void sendpsbt_done(struct bitcoind *bitcoind UNUSED,
 	was_pending(command_success(sending->cmd, response));
 }
 
+static struct command_result *json_dev_finalizepsbt(struct command *cmd,
+						    const char *buffer,
+						    const jsmntok_t *obj,
+						    const jsmntok_t *params)
+{
+	struct wally_psbt *psbt;
+	struct wally_tx *wtx;
+	struct bitcoin_txid txid;
+	struct json_stream *response;
+
+	if (!param_check(cmd, buffer, params,
+			 p_req("psbt", param_psbt, &psbt),
+			 NULL))
+		return command_param_failed();
+
+	if (!psbt_finalize(psbt))
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "PSBT not finalizeable");
+
+	wtx = psbt_final_tx(cmd, psbt);
+	wally_txid(wtx, &txid);
+
+	response = json_stream_success(cmd);
+	json_add_psbt(response, "psbt", psbt);
+	json_add_hex_talarr(response, "tx", linearize_wtx(tmpctx, wtx));
+	json_add_txid(response, "txid", &txid);
+	return command_success(cmd, response);
+}
+
+static const struct json_command dev_finalizepsbt_command = {
+	"dev-finalizepsbt",
+	json_dev_finalizepsbt,
+	true,
+};
+AUTODATA(json_command, &dev_finalizepsbt_command);
+
 static struct command_result *json_sendpsbt(struct command *cmd,
 					    const char *buffer,
 					    const jsmntok_t *obj,