perf(document): remove some more unnecessary cloning in $toObject() re: #14394

Author: vkarpov15

lib/document.js

@@ -3780,7 +3780,7 @@ Document.prototype.$__handleReject = function handleReject(err) {
  */
 
 Document.prototype.$toObject = function(options, json) {
-  let defaultOptions = {
+  const defaultOptions = {
     transform: true,
     flattenDecimals: true
   };
@@ -3793,7 +3793,7 @@ Document.prototype.$toObject = function(options, json) {
   const schemaOptions = this.$__schema && this.$__schema.options || {};
   // merge base default options with Schema's set default options if available.
   // `clone` is necessary here because `utils.options` directly modifies the second input.
-  defaultOptions = { ...defaultOptions, ...baseOptions, ...schemaOptions[path] };
+  Object.assign(defaultOptions, baseOptions, schemaOptions[path]);
 
   // If options do not exist or is not an object, set it to empty object
   options = utils.isPOJO(options) ? { ...options } : {};
@@ -3865,27 +3865,25 @@ Document.prototype.$toObject = function(options, json) {
   options.minimize = _minimize;
 
   cloneOptions._parentOptions = options;
-  cloneOptions._skipSingleNestedGetters = false;
-
-  const gettersOptions = Object.assign({}, cloneOptions);
-  gettersOptions._skipSingleNestedGetters = true;
 
+  cloneOptions._skipSingleNestedGetters = false;
   // remember the root transform function
   // to save it from being overwritten by sub-transform functions
   const originalTransform = options.transform;
 
   let ret = clone(this._doc, cloneOptions) || {};
 
+  cloneOptions._skipSingleNestedGetters = true;
   if (options.getters) {
-    applyGetters(this, ret, gettersOptions);
+    applyGetters(this, ret, cloneOptions);
 
     if (options.minimize) {
       ret = minimize(ret) || {};
     }
   }
 
   if (options.virtuals || (options.getters && options.virtuals !== false)) {
-    applyVirtuals(this, ret, gettersOptions, options);
+    applyVirtuals(this, ret, cloneOptions, options);
   }
 
   if (options.versionKey === false && this.$__schema.options.versionKey) {