[rpc] Add change_type option to fundrawtransaction

Author: promag

src/wallet/rpcwallet.cpp

@@ -3057,6 +3057,7 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
                             "   {\n"
                             "     \"changeAddress\"          (string, optional, default pool address) The bitcoin address to receive the change\n"
                             "     \"changePosition\"         (numeric, optional, default random) The index of the change output\n"
+                            "     \"change_type\"            (string, optional) The output type to use. Only valid if changeAddress is not specified. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\". Default is set by -changetype.\n"
                             "     \"includeWatching\"        (boolean, optional, default false) Also select inputs which are watch only\n"
                             "     \"lockUnspents\"           (boolean, optional, default false) Lock selected unspent outputs\n"
                             "     \"feeRate\"                (numeric, optional, default not set: makes wallet determine the fee) Set a specific fee rate in " + CURRENCY_UNIT + "/kB\n"
@@ -3122,6 +3123,7 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
             {
                 {"changeAddress", UniValueType(UniValue::VSTR)},
                 {"changePosition", UniValueType(UniValue::VNUM)},
+                {"change_type", UniValueType(UniValue::VSTR)},
                 {"includeWatching", UniValueType(UniValue::VBOOL)},
                 {"lockUnspents", UniValueType(UniValue::VBOOL)},
                 {"reserveChangeKey", UniValueType(UniValue::VBOOL)}, // DEPRECATED (and ignored), should be removed in 0.16 or so.
@@ -3146,6 +3148,16 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
         if (options.exists("changePosition"))
             changePosition = options["changePosition"].get_int();
 
+        if (options.exists("change_type")) {
+            if (options.exists("changeAddress")) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both changeAddress and address_type options");
+            }
+            coinControl.change_type = ParseOutputType(options["change_type"].get_str(), coinControl.change_type);
+            if (coinControl.change_type == OUTPUT_TYPE_NONE) {
+                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Unknown change type '%s'", options["change_type"].get_str()));
+            }
+        }
+
         if (options.exists("includeWatching"))
             coinControl.fAllowWatchOnly = options["includeWatching"].get_bool();