rpcclient: serialize nil inputs to empty list

btcjson/chainsvrcmds.go

@@ -63,10 +63,15 @@ type CreateRawTransactionCmd struct {
 // NewCreateRawTransactionCmd returns a new instance which can be used to issue
 // a createrawtransaction JSON-RPC command.
 //
-// Amounts are in BTC.
+// Amounts are in BTC. Passing in nil and the empty slice as inputs is equivalent,
+// both gets interpreted as the empty slice.
 func NewCreateRawTransactionCmd(inputs []TransactionInput, amounts map[string]float64,
 	lockTime *int64) *CreateRawTransactionCmd {
-
+	// to make sure we're serializing this to the empty list and not null, we
+	// explicitly initialize the list
+	if inputs == nil {
+		inputs = []TransactionInput{}
+	}
 	return &CreateRawTransactionCmd{
 		Inputs:   inputs,
 		Amounts:  amounts,

btcjson/chainsvrcmds_test.go

@@ -60,6 +60,21 @@ func TestChainSvrCmds(t *testing.T) {
 				Amounts: map[string]float64{"456": .0123},
 			},
 		},
+		{
+			name: "createrawtransaction - no inputs",
+			newCmd: func() (interface{}, error) {
+				return btcjson.NewCmd("createrawtransaction", `[]`, `{"456":0.0123}`)
+			},
+			staticCmd: func() interface{} {
+				amounts := map[string]float64{"456": .0123}
+				return btcjson.NewCreateRawTransactionCmd(nil, amounts, nil)
+			},
+			marshalled: `{"jsonrpc":"1.0","method":"createrawtransaction","params":[[],{"456":0.0123}],"id":1}`,
+			unmarshalled: &btcjson.CreateRawTransactionCmd{
+				Inputs:  []btcjson.TransactionInput{},
+				Amounts: map[string]float64{"456": .0123},
+			},
+		},
 		{
 			name: "createrawtransaction optional",
 			newCmd: func() (interface{}, error) {

rpcclient/rawtransactions.go

@@ -261,7 +261,8 @@ func (c *Client) CreateRawTransactionAsync(inputs []btcjson.TransactionInput,
 }
 
 // CreateRawTransaction returns a new transaction spending the provided inputs
-// and sending to the provided addresses.
+// and sending to the provided addresses. If the inputs are either nil or an
+// empty slice, it is interpreted as an empty slice.
 func (c *Client) CreateRawTransaction(inputs []btcjson.TransactionInput,
 	amounts map[btcutil.Address]btcutil.Amount, lockTime *int64) (*wire.MsgTx, error) {