Add code to test for allowable types in json rpc id field along with test code for the new function.

jsonapi.go

@@ -723,3 +723,22 @@ func RpcCommand(user string, password string, server string, message []byte) (Re
 	}
 	return result, err
 }
+
+// IsValidIdType checks that the Id field (which can go in any of the json
+// messages is valid.  json rpc 1.0 allows any (json) type, but we still need
+// to prevent values that cannot be marshalled from going in.  json rpc 2.0
+// (which bitcoind follows for some parts) only allows string, number, or null,
+// so we restrict to that list.  Ths is only necessary if you manually marshal
+// a message.  The normal btcjson functions only use string ids.
+func IsValidIdType(id interface{}) bool {
+	switch id.(type) {
+	case int, int8, int16, int32, int64,
+		uint, uint8, uint16, uint32, uint64,
+		float32, float64,
+		string,
+		nil:
+		return true
+	default:
+		return false
+	}
+}

jsonapi_test.go

@@ -243,3 +243,26 @@ func TestRpcReply(t *testing.T) {
 	}
 	return
 }
+
+var idtests = []struct {
+	testId []interface{}
+	pass   bool
+}{
+	{[]interface{}{"string test"}, true},
+	{[]interface{}{1}, true},
+	{[]interface{}{1.0}, true},
+	{[]interface{}{nil}, true},
+	{[]interface{}{make(chan int)}, false},
+}
+
+// TestIsValidIdType tests that IsValidIdType allows (and disallows the correct
+// types.
+func TestIsValidIdType(t *testing.T) {
+	for _, tt := range idtests {
+		res := btcjson.IsValidIdType(tt.testId[0])
+		if res != tt.pass {
+			t.Errorf("Incorrect type result %v.", tt)
+		}
+	}
+	return
+}