Changes

node_modules/mongoose/lib/schema/documentarray.js

@@ -361,6 +361,11 @@ DocumentArrayPath.prototype.cast = function(value, doc, init, prev, options) {
   // lazy load
   MongooseDocumentArray || (MongooseDocumentArray = require('../types/documentarray'));
 
+  // Skip casting if `value` is the same as the previous value, no need to cast. See gh-9266
+  if (value != null && value[arrayPathSymbol] != null && value === prev) {
+    return value;
+  }
+
   let selected;
   let subdoc;
   const _opts = { transform: false, virtuals: false };
@@ -513,6 +518,26 @@ function scopePaths(array, fields, init) {
   return hasKeys && selected || undefined;
 }
 
+/**
+ * Sets a default option for all DocumentArray instances.
+ *
+ * ####Example:
+ *
+ *     // Make all numbers have option `min` equal to 0.
+ *     mongoose.Schema.DocumentArray.set('_id', false);
+ *
+ * @param {String} option - The option you'd like to set the value for
+ * @param {*} value - value for option
+ * @return {undefined}
+ * @function set
+ * @static
+ * @api public
+ */
+
+DocumentArrayPath.defaultOptions = {};
+
+DocumentArrayPath.set = SchemaType.set;
+
 /*!
  * Module exports.
  */