[ENHANCEMENT] Return native Promise for methods if no callback is supplied.

Author: scoin

lib/rpccall.js

@@ -22,23 +22,38 @@ module.exports = (connection) => {
 
                 params = parseParams(commands[command], args);
 
-            } else if (args instanceof Function && !cb) {
-
-                cb = args;
-
             } else if (Array.isArray(args) || args === null || args === undefined) {
 
                 params = args;
 
-            } else {
+            } else if (args instanceof Function && !cb) {
+
+                cb = args;
+
+            } else if(args != undefined) {
 
                 throw `${args} is invalid input.`
 
             }
 
-            client.call(command.toLowerCase(), params, (err, res) => {
-                cb(err, res);
-            })
+            let promiseReturn = null;
+
+            if(!cb){
+                promiseReturn = new Promise((resolve, reject) => {
+                    cb = (err, res) => {
+                        if(err){
+                            return reject(err);
+                        }
+                        resolve(res);
+                    }
+                })
+            }
+
+
+            client.call(command.toLowerCase(), params, cb);
+
+            return promiseReturn;
+
         }
     }
     return caller;