some progress

node_modules/mongoose/lib/error/objectExpected.js

@@ -0,0 +1,30 @@
+/*!
+ * Module dependencies.
+ */
+
+'use strict';
+
+const MongooseError = require('./');
+
+
+class ObjectExpectedError extends MongooseError {
+  /**
+   * Strict mode error constructor
+   *
+   * @param {string} type
+   * @param {string} value
+   * @api private
+   */
+  constructor(path, val) {
+    const typeDescription = Array.isArray(val) ? 'array' : 'primitive value';
+    super('Tried to set nested object field `' + path +
+      `\` to ${typeDescription} \`` + val + '`');
+    this.path = path;
+  }
+}
+
+Object.defineProperty(ObjectExpectedError.prototype, 'name', {
+  value: 'ObjectExpectedError'
+});
+
+module.exports = ObjectExpectedError;