mongoose/lib/schema.js

Mongoose MongoDB ODM

'use strict';

/*!
 * Module dependencies.
 */

const EventEmitter = require('events').EventEmitter;
const Kareem = require('kareem');
const MongooseError = require('./error/mongooseError');
const SchemaType = require('./schemaType');
const SchemaTypeOptions = require('./options/schemaTypeOptions');
const VirtualOptions = require('./options/virtualOptions');
const VirtualType = require('./virtualType');
const addAutoId = require('./helpers/schema/addAutoId');
const clone = require('./helpers/clone');
const get = require('./helpers/get');
const getConstructorName = require('./helpers/getConstructorName');
const getIndexes = require('./helpers/schema/getIndexes');
const handleReadPreferenceAliases = require('./helpers/query/handleReadPreferenceAliases');
const idGetter = require('./helpers/schema/idGetter');
const isIndexSpecEqual = require('./helpers/indexes/isIndexSpecEqual');
const merge = require('./helpers/schema/merge');
const mpath = require('mpath');
const setPopulatedVirtualValue = require('./helpers/populate/setPopulatedVirtualValue');
const setupTimestamps = require('./helpers/timestamps/setupTimestamps');
const utils = require('./utils');
const validateRef = require('./helpers/populate/validateRef');

const hasNumericSubpathRegex = /\.\d+(\.|$)/;

let MongooseTypes;

const queryHooks = require('./constants').queryMiddlewareFunctions;
const documentHooks = require('./helpers/model/applyHooks').middlewareFunctions;
const hookNames = queryHooks.concat(documentHooks).
  reduce((s, hook) => s.add(hook), new Set());

const isPOJO = utils.isPOJO;

let id = 0;

const numberRE = /^\d+$/;

/**
 * Schema constructor.
 *
 * #### Example:
 *
 *     const child = new Schema({ name: String });
 *     const schema = new Schema({ name: String, age: Number, children: [child] });
 *     const Tree = mongoose.model('Tree', schema);
 *
 *     // setting schema options
 *     new Schema({ name: String }, { id: false, autoIndex: false })
 *
 * #### Options:
 *
 * - [autoIndex](https://mongoosejs.com/docs/guide.html#autoIndex): bool - defaults to null (which means use the connection's autoIndex option)
 * - [autoCreate](https://mongoosejs.com/docs/guide.html#autoCreate): bool - defaults to null (which means use the connection's autoCreate option)
 * - [bufferCommands](https://mongoosejs.com/docs/guide.html#bufferCommands): bool - defaults to true
 * - [bufferTimeoutMS](https://mongoosejs.com/docs/guide.html#bufferTimeoutMS): number - defaults to 10000 (10 seconds). If `bufferCommands` is enabled, the amount of time Mongoose will wait for connectivity to be restablished before erroring out.
 * - [capped](https://mongoosejs.com/docs/guide.html#capped): bool | number | object - defaults to false
 * - [collection](https://mongoosejs.com/docs/guide.html#collection): string - no default
 * - [discriminatorKey](https://mongoosejs.com/docs/guide.html#discriminatorKey): string - defaults to `__t`
 * - [id](https://mongoosejs.com/docs/guide.html#id): bool - defaults to true
 * - [_id](https://mongoosejs.com/docs/guide.html#_id): bool - defaults to true
 * - [minimize](https://mongoosejs.com/docs/guide.html#minimize): bool - controls [document#toObject](https://mongoosejs.com/docs/api/document.html#Document.prototype.toObject()) behavior when called manually - defaults to true
 * - [read](https://mongoosejs.com/docs/guide.html#read): string
 * - [readConcern](https://mongoosejs.com/docs/guide.html#readConcern): object - defaults to null, use to set a default [read concern](https://www.mongodb.com/docs/manual/reference/read-concern/) for all queries.
 * - [writeConcern](https://mongoosejs.com/docs/guide.html#writeConcern): object - defaults to null, use to override [the MongoDB server's default write concern settings](https://www.mongodb.com/docs/manual/reference/write-concern/)
 * - [shardKey](https://mongoosejs.com/docs/guide.html#shardKey): object - defaults to `null`
 * - [strict](https://mongoosejs.com/docs/guide.html#strict): bool - defaults to true
 * - [strictQuery](https://mongoosejs.com/docs/guide.html#strictQuery): bool - defaults to false
 * - [toJSON](https://mongoosejs.com/docs/guide.html#toJSON) - object - no default
 * - [toObject](https://mongoosejs.com/docs/guide.html#toObject) - object - no default
 * - [typeKey](https://mongoosejs.com/docs/guide.html#typeKey) - string - defaults to 'type'
 * - [validateBeforeSave](https://mongoosejs.com/docs/guide.html#validateBeforeSave) - bool - defaults to `true`
 * - [validateModifiedOnly](https://mongoosejs.com/docs/api/document.html#Document.prototype.validate()) - bool - defaults to `false`
 * - [versionKey](https://mongoosejs.com/docs/guide.html#versionKey): string or object - defaults to "__v"
 * - [optimisticConcurrency](https://mongoosejs.com/docs/guide.html#optimisticConcurrency): bool - defaults to false. Set to true to enable [optimistic concurrency](https://thecodebarbarian.com/whats-new-in-mongoose-5-10-optimistic-concurrency.html).
 * - [collation](https://mongoosejs.com/docs/guide.html#collation): object - defaults to null (which means use no collation)
 * - [timeseries](https://mongoosejs.com/docs/guide.html#timeseries): object - defaults to null (which means this schema's collection won't be a timeseries collection)
 * - [selectPopulatedPaths](https://mongoosejs.com/docs/guide.html#selectPopulatedPaths): boolean - defaults to `true`
 * - [skipVersioning](https://mongoosejs.com/docs/guide.html#skipVersioning): object - paths to exclude from versioning
 * - [timestamps](https://mongoosejs.com/docs/guide.html#timestamps): object or boolean - defaults to `false`. If true, Mongoose adds `createdAt` and `updatedAt` properties to your schema and manages those properties for you.
 * - [pluginTags](https://mongoosejs.com/docs/guide.html#pluginTags): array of strings - defaults to `undefined`. If set and plugin called with `tags` option, will only apply that plugin to schemas with a matching tag.
 * - [virtuals](https://mongoosejs.com/docs/tutorials/virtuals.html#virtuals-via-schema-options): object - virtuals to define, alias for [`.virtual`](https://mongoosejs.com/docs/api/schema.html#Schema.prototype.virtual())
 * - [collectionOptions]: object with options passed to [`createCollection()`](https://www.mongodb.com/docs/manual/reference/method/db.createCollection/) when calling `Model.createCollection()` or `autoCreate` set to true.
 *
 * #### Options for Nested Schemas:
 *
 * - `excludeIndexes`: bool - defaults to `false`. If `true`, skip building indexes on this schema's paths.
 *
 * #### Note:
 *
 * _When nesting schemas, (`children` in the example above), always declare the child schema first before passing it into its parent._
 *
 * @param {Object|Schema|Array} [definition] Can be one of: object describing schema paths, or schema to copy, or array of objects and schemas
 * @param {Object} [options]
 * @inherits NodeJS EventEmitter https://nodejs.org/api/events.html#class-eventemitter
 * @event `init`: Emitted after the schema is compiled into a `Model`.
 * @api public
 */

function Schema(obj, options) {
  if (!(this instanceof Schema)) {
    return new Schema(obj, options);
  }

  this.obj = obj;
  this.paths = {};
  this.aliases = {};
  this.subpaths = {};
  this.virtuals = {};
  this.singleNestedPaths = {};
  this.nested = {};
  this.inherits = {};
  this.callQueue = [];
  this._indexes = [];
  this._searchIndexes = [];
  this.methods = (options && options.methods) || {};
  this.methodOptions = {};
  this.statics = (options && options.statics) || {};
  this.tree = {};
  this.query = (options && options.query) || {};
  this.childSchemas = [];
  this.plugins = [];
  // For internal debugging. Do not use this to try to save a schema in MDB.
  this.$id = ++id;
  this.mapPaths = [];

  this.s = {
    hooks: new Kareem()
  };
  this.options = this.defaultOptions(options);

  // build paths
  if (Array.isArray(obj)) {
    for (const definition of obj) {
      this.add(definition);
    }
  } else if (obj) {
    this.add(obj);
  }

  // build virtual paths
  if (options && options.virtuals) {
    const virtuals = options.virtuals;
    const pathNames = Object.keys(virtuals);
    for (const pathName of pathNames) {
      const pathOptions = virtuals[pathName].options ? virtuals[pathName].options : undefined;
      const virtual = this.virtual(pathName, pathOptions);

      if (virtuals[pathName].get) {
        virtual.get(virtuals[pathName].get);
      }

      if (virtuals[pathName].set) {
        virtual.set(virtuals[pathName].set);
      }
    }
  }

  // check if _id's value is a subdocument (gh-2276)
  const _idSubDoc = obj && obj._id && utils.isObject(obj._id);

  // ensure the documents get an auto _id unless disabled
  const auto_id = !this.paths['_id'] &&
      (this.options._id) && !_idSubDoc;

  if (auto_id) {
    addAutoId(this);
  }

  this.setupTimestamp(this.options.timestamps);
}

/**
 * Create virtual properties with alias field
 * @api private
 */
function aliasFields(schema, paths) {
  for (const path of Object.keys(paths)) {
    let alias = null;
    if (paths[path] != null) {
      alias = paths[path];
    } else {
      const options = get(schema.paths[path], 'options');
      if (options == null) {
        continue;
      }

      alias = options.alias;
    }

    if (!alias) {
      continue;
    }

    const prop = schema.paths[path].path;
    if (Array.isArray(alias)) {
      for (const a of alias) {
        if (typeof a !== 'string') {
          throw new Error('Invalid value for alias option on ' + prop + ', got ' + a);
        }

        schema.aliases[a] = prop;

        schema.
          virtual(a).
          get((function(p) {
            return function() {
              if (typeof this.get === 'function') {
                return this.get(p);
              }
              return this[p];
            };
          })(prop)).
          set((function(p) {
            return function(v) {
              return this.$set(p, v);
            };
          })(prop));
      }

      continue;
    }

    if (typeof alias !== 'string') {
      throw new Error('Invalid value for alias option on ' + prop + ', got ' + alias);
    }

    schema.aliases[alias] = prop;

    schema.
      virtual(alias).
      get((function(p) {
        return function() {
          if (typeof this.get === 'function') {
            return this.get(p);
          }
          return this[p];
        };
      })(prop)).
      set((function(p) {
        return function(v) {
          return this.$set(p, v);
        };
      })(prop));
  }
}

/*!
 * Inherit from EventEmitter.
 */
Schema.prototype = Object.create(EventEmitter.prototype);
Schema.prototype.constructor = Schema;
Schema.prototype.instanceOfSchema = true;

/*!
 * ignore
 */

Object.defineProperty(Schema.prototype, '$schemaType', {
  configurable: false,
  enumerable: false,
  writable: true
});

/**
 * Array of child schemas (from document arrays and single nested subdocs)
 * and their corresponding compiled models. Each element of the array is
 * an object with 2 properties: `schema` and `model`.
 *
 * This property is typically only useful for plugin authors and advanced users.
 * You do not need to interact with this property at all to use mongoose.
 *
 * @api public
 * @property childSchemas
 * @memberOf Schema
 * @instance
 */

Object.defineProperty(Schema.prototype, 'childSchemas', {
  configurable: false,
  enumerable: true,
  writable: true
});

/**
 * Object containing all virtuals defined on this schema.
 * The objects' keys are the virtual paths and values are instances of `VirtualType`.
 *
 * This property is typically only useful for plugin authors and advanced users.
 * You do not need to interact with this property at all to use mongoose.
 *
 * #### Example:
 *
 *     const schema = new Schema({});
 *     schema.virtual('answer').get(() => 42);
 *
 *     console.log(schema.virtuals); // { answer: VirtualType { path: 'answer', ... } }
 *     console.log(schema.virtuals['answer'].getters[0].call()); // 42
 *
 * @api public
 * @property virtuals
 * @memberOf Schema
 * @instance
 */

Object.defineProperty(Schema.prototype, 'virtuals', {
  configurable: false,
  enumerable: true,
  writable: true
});

/**
 * The original object passed to the schema constructor
 *
 * #### Example:
 *
 *     const schema = new Schema({ a: String }).add({ b: String });
 *     schema.obj; // { a: String }
 *
 * @api public
 * @property obj
 * @memberOf Schema
 * @instance
 */

Schema.prototype.obj;

/**
 * The paths defined on this schema. The keys are the top-level paths
 * in this schema, and the values are instances of the SchemaType class.
 *
 * #### Example:
 *
 *     const schema = new Schema({ name: String }, { _id: false });
 *     schema.paths; // { name: SchemaString { ... } }
 *
 *     schema.add({ age: Number });
 *     schema.paths; // { name: SchemaString { ... }, age: SchemaNumber { ... } }
 *
 * @api public
 * @property paths
 * @memberOf Schema
 * @instance
 */

Schema.prototype.paths;

/**
 * Schema as a tree
 *
 * #### Example:
 *
 *     {
 *         '_id'     : ObjectId
 *       , 'nested'  : {
 *             'key' : String
 *         }
 *     }
 *
 * @api private
 * @property tree
 * @memberOf Schema
 * @instance
 */

Schema.prototype.tree;

/**
 * Returns a deep copy of the schema
 *
 * #### Example:
 *
 *     const schema = new Schema({ name: String });
 *     const clone = schema.clone();
 *     clone === schema; // false
 *     clone.path('name'); // SchemaString { ... }
 *
 * @return {Schema} the cloned schema
 * @api public
 * @memberOf Schema
 * @instance
 */

Schema.prototype.clone = function() {
  const s = this._clone();

  // Bubble up `init` for backwards compat
  s.on('init', v => this.emit('init', v));

  return s;
};

/*!
 * ignore
 */

Schema.prototype._clone = function _clone(Constructor) {
  Constructor = Constructor || (this.base == null ? Schema : this.base.Schema);

  const s = new Constructor({}, this._userProvidedOptions);
  s.base = this.base;
  s.obj = this.obj;
  s.options = clone(this.options);
  s.callQueue = this.callQueue.map(function(f) { return f; });
  s.methods = clone(this.methods);
  s.methodOptions = clone(this.methodOptions);
  s.statics = clone(this.statics);
  s.query = clone(this.query);
  s.plugins = Array.prototype.slice.call(this.plugins);
  s._indexes = clone(this._indexes);
  s._searchIndexes = clone(this._searchIndexes);
  s.s.hooks = this.s.hooks.clone();

  s.tree = clone(this.tree);
  s.paths = Object.fromEntries(
    Object.entries(this.paths).map(([key, value]) => ([key, value.clone()]))
  );
  s.nested = clone(this.nested);
  s.subpaths = clone(this.subpaths);
  for (const schemaType of Object.values(s.paths)) {
    if (schemaType.$isSingleNested) {
      const path = schemaType.path;
      for (const key of Object.keys(schemaType.schema.paths)) {
        s.singleNestedPaths[path + '.' + key] = schemaType.schema.paths[key];
      }
      for (const key of Object.keys(schemaType.schema.singleNestedPaths)) {
        s.singleNestedPaths[path + '.' + key] =
          schemaType.schema.singleNestedPaths[key];
      }
      for (const key of Object.keys(schemaType.schema.subpaths)) {
        s.singleNestedPaths[path + '.' + key] =
          schemaType.schema.subpaths[key];
      }
      for (const key of Object.keys(schemaType.schema.nested)) {
        s.singleNestedPaths[path + '.' + key] = 'nested';
      }
    }
  }
  s._gatherChildSchemas();

  s.virtuals = clone(this.virtuals);
  s.$globalPluginsApplied = this.$globalPluginsApplied;
  s.$isRootDiscriminator = this.$isRootDiscriminator;
  s.$implicitlyCreated = this.$implicitlyCreated;
  s.$id = ++id;
  s.$originalSchemaId = this.$id;
  s.mapPaths = [].concat(this.mapPaths);

  if (this.discriminatorMapping != null) {
    s.discriminatorMapping = Object.assign({}, this.discriminatorMapping);
  }
  if (this.discriminators != null) {
    s.discriminators = Object.assign({}, this.discriminators);
  }
  if (this._applyDiscriminators != null) {
    s._applyDiscriminators = new Map(this._applyDiscriminators);
  }

  s.aliases = Object.assign({}, this.aliases);

  return s;
};

/**
 * Returns a new schema that has the picked `paths` from this schema.
 *
 * This method is analagous to [Lodash's `pick()` function](https://lodash.com/docs/4.17.15#pick) for Mongoose schemas.
 *
 * #### Example:
 *
 *     const schema = Schema({ name: String, age: Number });
 *     // Creates a new schema with the same `name` path as `schema`,
 *     // but no `age` path.
 *     const newSchema = schema.pick(['name']);
 *
 *     newSchema.path('name'); // SchemaString { ... }
 *     newSchema.path('age'); // undefined
 *
 * @param {String[]} paths List of Paths to pick for the new Schema
 * @param {Object} [options] Options to pass to the new Schema Constructor (same as `new Schema(.., Options)`). Defaults to `this.options` if not set.
 * @return {Schema}
 * @api public
 */

Schema.prototype.pick = function(paths, options) {
  const newSchema = new Schema({}, options || this.options);
  if (!Array.isArray(paths)) {
    throw new MongooseError('Schema#pick() only accepts an array argument, ' +
      'got "' + typeof paths + '"');
  }

  for (const path of paths) {
    if (this.nested[path]) {
      newSchema.add({ [path]: get(this.tree, path) });
    } else {
      const schematype = this.path(path);
      if (schematype == null) {
        throw new MongooseError('Path `' + path + '` is not in the schema');
      }
      newSchema.add({ [path]: schematype });
    }
  }

  return newSchema;
};

/**
 * Returns a new schema that has the `paths` from the original schema, minus the omitted ones.
 *
 * This method is analagous to [Lodash's `omit()` function](https://lodash.com/docs/#omit) for Mongoose schemas.
 *
 * #### Example:
 *
 *     const schema = Schema({ name: String, age: Number });
 *     // Creates a new schema omitting the `age` path
 *     const newSchema = schema.omit(['age']);
 *
 *     newSchema.path('name'); // SchemaString { ... }
 *     newSchema.path('age'); // undefined
 *
 * @param {String[]} paths List of Paths to omit for the new Schema
 * @param {Object} [options] Options to pass to the new Schema Constructor (same as `new Schema(.., Options)`). Defaults to `this.options` if not set.
 * @return {Schema}
 * @api public
 */

Schema.prototype.omit = function(paths, options) {
  const newSchema = new Schema(this, options || this.options);
  if (!Array.isArray(paths)) {
    throw new MongooseError(
      'Schema#omit() only accepts an array argument, ' +
        'got "' +
        typeof paths +
        '"'
    );
  }

  newSchema.remove(paths);

  for (const nested in newSchema.singleNestedPaths) {
    if (paths.includes(nested)) {
      delete newSchema.singleNestedPaths[nested];
    }
  }

  return newSchema;
};

/**
 * Returns default options for this schema, merged with `options`.
 *
 * @param {Object} [options] Options to overwrite the default options
 * @return {Object} The merged options of `options` and the default options
 * @api private
 */

Schema.prototype.defaultOptions = function(options) {
  this._userProvidedOptions = options == null ? {} : clone(options);
  const baseOptions = this.base && this.base.options || {};
  const strict = 'strict' in baseOptions ? baseOptions.strict : true;
  const strictQuery = 'strictQuery' in baseOptions ? baseOptions.strictQuery : false;
  const id = 'id' in baseOptions ? baseOptions.id : true;
  options = {
    strict,
    strictQuery,
    bufferCommands: true,
    capped: false, // { size, max, autoIndexId }
    versionKey: '__v',
    optimisticConcurrency: false,
    minimize: true,
    autoIndex: null,
    discriminatorKey: '__t',
    shardKey: null,
    read: null,
    validateBeforeSave: true,
    validateModifiedOnly: false,
    // the following are only applied at construction time
    _id: true,
    id: id,
    typeKey: 'type',
    ...options
  };

  if (options.versionKey && typeof options.versionKey !== 'string') {
    throw new MongooseError('`versionKey` must be falsy or string, got `' + (typeof options.versionKey) + '`');
  }

  if (typeof options.read === 'string') {
    options.read = handleReadPreferenceAliases(options.read);
  } else if (Array.isArray(options.read) && typeof options.read[0] === 'string') {
    options.read = {
      mode: handleReadPreferenceAliases(options.read[0]),
      tags: options.read[1]
    };
  }

  if (options.optimisticConcurrency && !options.versionKey) {
    throw new MongooseError('Must set `versionKey` if using `optimisticConcurrency`');
  }

  return options;
};

/**
 * Inherit a Schema by applying a discriminator on an existing Schema.
 *
 *
 * #### Example:
 *
 *     const eventSchema = new mongoose.Schema({ timestamp: Date }, { discriminatorKey: 'kind' });
 *
 *     const clickedEventSchema = new mongoose.Schema({ element: String }, { discriminatorKey: 'kind' });
 *     const ClickedModel = eventSchema.discriminator('clicked', clickedEventSchema);
 *
 *     const Event = mongoose.model('Event', eventSchema);
 *
 *     Event.discriminators['clicked']; // Model { clicked }
 *
 *     const doc = await Event.create({ kind: 'clicked', element: '#hero' });
 *     doc.element; // '#hero'
 *     doc instanceof ClickedModel; // true
 *
 * @param {String} name the name of the discriminator
 * @param {Schema} schema the discriminated Schema
 * @param {Object} [options] discriminator options
 * @param {String} [options.value] the string stored in the `discriminatorKey` property. If not specified, Mongoose uses the `name` parameter.
 * @param {Boolean} [options.clone=true] By default, `discriminator()` clones the given `schema`. Set to `false` to skip cloning.
 * @param {Boolean} [options.overwriteModels=false] by default, Mongoose does not allow you to define a discriminator with the same name as another discriminator. Set this to allow overwriting discriminators with the same name.
 * @param {Boolean} [options.mergeHooks=true] By default, Mongoose merges the base schema's hooks with the discriminator schema's hooks. Set this option to `false` to make Mongoose use the discriminator schema's hooks instead.
 * @param {Boolean} [options.mergePlugins=true] By default, Mongoose merges the base schema's plugins with the discriminator schema's plugins. Set this option to `false` to make Mongoose use the discriminator schema's plugins instead.
 * @return {Schema} the Schema instance
 * @api public
 */
Schema.prototype.discriminator = function(name, schema, options) {
  this._applyDiscriminators = this._applyDiscriminators || new Map();
  this._applyDiscriminators.set(name, { schema, options });

  return this;
};

/*!
 * Get this schema's default toObject/toJSON options, including Mongoose global
 * options.
 */

Schema.prototype._defaultToObjectOptions = function(json) {
  const path = json ? 'toJSON' : 'toObject';
  if (this._defaultToObjectOptionsMap && this._defaultToObjectOptionsMap[path]) {
    return this._defaultToObjectOptionsMap[path];
  }

  const baseOptions = this.base &&
    this.base.options &&
    this.base.options[path] || {};
  const schemaOptions = this.options[path] || {};
  // merge base default options with Schema's set default options if available.
  // `clone` is necessary here because `utils.options` directly modifies the second input.
  const defaultOptions = Object.assign({}, baseOptions, schemaOptions);

  this._defaultToObjectOptionsMap = this._defaultToObjectOptionsMap || {};
  this._defaultToObjectOptionsMap[path] = defaultOptions;
  return defaultOptions;
};

/**
 * Adds key path / schema type pairs to this schema.
 *
 * #### Example:
 *
 *     const ToySchema = new Schema();
 *     ToySchema.add({ name: 'string', color: 'string', price: 'number' });
 *
 *     const TurboManSchema = new Schema();
 *     // You can also `add()` another schema and copy over all paths, virtuals,
 *     // getters, setters, indexes, methods, and statics.
 *     TurboManSchema.add(ToySchema).add({ year: Number });
 *
 * @param {Object|Schema} obj plain object with paths to add, or another schema
 * @param {String} [prefix] path to prefix the newly added paths with
 * @return {Schema} the Schema instance
 * @api public
 */

Schema.prototype.add = function add(obj, prefix) {
  if (obj instanceof Schema || (obj != null && obj.instanceOfSchema)) {
    merge(this, obj);

    return this;
  }

  // Special case: setting top-level `_id` to false should convert to disabling
  // the `_id` option. This behavior never worked before 5.4.11 but numerous
  // codebases use it (see gh-7516, gh-7512).
  if (obj._id === false && prefix == null) {
    this.options._id = false;
  }

  prefix = prefix || '';
  // avoid prototype pollution
  if (prefix === '__proto__.' || prefix === 'constructor.' || prefix === 'prototype.') {
    return this;
  }

  const keys = Object.keys(obj);
  const typeKey = this.options.typeKey;
  for (const key of keys) {
    if (utils.specialProperties.has(key)) {
      continue;
    }

    const fullPath = prefix + key;
    const val = obj[key];

    if (val == null) {
      throw new TypeError('Invalid value for schema path `' + fullPath +
        '`, got value "' + val + '"');
    }
    // Retain `_id: false` but don't set it as a path, re: gh-8274.
    if (key === '_id' && val === false) {
      continue;
    }
    // Deprecate setting schema paths to primitive types (gh-7558)
    let isMongooseTypeString = false;
    if (typeof val === 'string') {
      // Handle the case in which the type is specified as a string (eg. 'date', 'oid', ...)
      const MongooseTypes = this.base != null ? this.base.Schema.Types : Schema.Types;
      const upperVal = val.charAt(0).toUpperCase() + val.substring(1);
      isMongooseTypeString = MongooseTypes[upperVal] != null;
    }
    if (
      key !== '_id' &&
      ((typeof val !== 'object' && typeof val !== 'function' && !isMongooseTypeString) ||
      val == null)
    ) {
      throw new TypeError(`Invalid schema configuration: \`${val}\` is not ` +
        `a valid type at path \`${key}\`. See ` +
        'https://bit.ly/mongoose-schematypes for a list of valid schema types.');
    }
    if (val instanceof VirtualType || (val.constructor && val.constructor.name || null) === 'VirtualType') {
      this.virtual(val);
      continue;
    }

    if (Array.isArray(val) && val.length === 1 && val[0] == null) {
      throw new TypeError('Invalid value for schema Array path `' + fullPath +
        '`, got value "' + val[0] + '"');
    }

    if (!(isPOJO(val) || val instanceof SchemaTypeOptions)) {
      // Special-case: Non-options definitely a path so leaf at this node
      // Examples: Schema instances, SchemaType instances
      if (prefix) {
        this.nested[prefix.substring(0, prefix.length - 1)] = true;
      }
      this.path(prefix + key, val);
      if (val[0] != null && !(val[0].instanceOfSchema) && utils.isPOJO(val[0].discriminators)) {
        const schemaType = this.path(prefix + key);
        for (const key in val[0].discriminators) {
          schemaType.discriminator(key, val[0].discriminators[key]);
        }
      }
    } else if (Object.keys(val).length < 1) {
      // Special-case: {} always interpreted as Mixed path so leaf at this node
      if (prefix) {
        this.nested[prefix.substring(0, prefix.length - 1)] = true;
      }
      this.path(fullPath, val); // mixed type
    } else if (!val[typeKey] || (typeKey === 'type' && isPOJO(val.type) && val.type.type)) {
      // Special-case: POJO with no bona-fide type key - interpret as tree of deep paths so recurse
      // nested object `{ last: { name: String } }`. Avoid functions with `.type` re: #10807 because
      // NestJS sometimes adds `Date.type`.
      this.nested[fullPath] = true;
      this.add(val, fullPath + '.');
    } else {
      // There IS a bona-fide type key that may also be a POJO
      const _typeDef = val[typeKey];
      if (isPOJO(_typeDef) && Object.keys(_typeDef).length > 0) {
        // If a POJO is the value of a type key, make it a subdocument
        if (prefix) {
          this.nested[prefix.substring(0, prefix.length - 1)] = true;
        }

        const childSchemaOptions = {};
        if (this._userProvidedOptions.typeKey) {
          childSchemaOptions.typeKey = this._userProvidedOptions.typeKey;
        }
        // propagate 'strict' option to child schema
        if (this._userProvidedOptions.strict != null) {
          childSchemaOptions.strict = this._userProvidedOptions.strict;
        }
        if (this._userProvidedOptions.toObject != null) {
          childSchemaOptions.toObject = utils.omit(this._userProvidedOptions.toObject, ['transform']);
        }
        if (this._userProvidedOptions.toJSON != null) {
          childSchemaOptions.toJSON = utils.omit(this._userProvidedOptions.toJSON, ['transform']);
        }

        const _schema = new Schema(_typeDef, childSchemaOptions);
        _schema.$implicitlyCreated = true;
        const schemaWrappedPath = Object.assign({}, val, { [typeKey]: _schema });
        this.path(prefix + key, schemaWrappedPath);
      } else {
        // Either the type is non-POJO or we interpret it as Mixed anyway
        if (prefix) {
          this.nested[prefix.substring(0, prefix.length - 1)] = true;
        }
        this.path(prefix + key, val);
        if (val != null && !(val.instanceOfSchema) && utils.isPOJO(val.discriminators)) {
          const schemaType = this.path(prefix + key);
          for (const key in val.discriminators) {
            schemaType.discriminator(key, val.discriminators[key]);
          }
        }
      }
    }
  }

  const aliasObj = Object.fromEntries(
    Object.entries(obj).map(([key]) => ([prefix + key, null]))
  );
  aliasFields(this, aliasObj);
  return this;
};

/**
 * Add an alias for `path`. This means getting or setting the `alias`
 * is equivalent to getting or setting the `path`.
 *
 * #### Example:
 *
 *     const toySchema = new Schema({ n: String });
 *
 *     // Make 'name' an alias for 'n'
 *     toySchema.alias('n', 'name');
 *
 *     const Toy = mongoose.model('Toy', toySchema);
 *     const turboMan = new Toy({ n: 'Turbo Man' });
 *
 *     turboMan.name; // 'Turbo Man'
 *     turboMan.n; // 'Turbo Man'
 *
 *     turboMan.name = 'Turbo Man Action Figure';
 *     turboMan.n; // 'Turbo Man Action Figure'
 *
 *     await turboMan.save(); // Saves { _id: ..., n: 'Turbo Man Action Figure' }
 *
 *
 * @param {String} path real path to alias
 * @param {String|String[]} alias the path(s) to use as an alias for `path`
 * @return {Schema} the Schema instance
 * @api public
 */

Schema.prototype.alias = function alias(path, alias) {
  aliasFields(this, { [path]: alias });
  return this;
};

/**
 * Remove an index by name or index specification.
 *
 * removeIndex only removes indexes from your schema object. Does **not** affect the indexes
 * in MongoDB.
 *
 * #### Example:
 *
 *     const ToySchema = new Schema({ name: String, color: String, price: Number });
 *
 *     // Add a new index on { name, color }
 *     ToySchema.index({ name: 1, color: 1 });
 *
 *     // Remove index on { name, color }
 *     // Keep in mind that order matters! `removeIndex({ color: 1, name: 1 })` won't remove the index
 *     ToySchema.removeIndex({ name: 1, color: 1 });
 *
 *     // Add an index with a custom name
 *     ToySchema.index({ color: 1 }, { name: 'my custom index name' });
 *     // Remove index by name
 *     ToySchema.removeIndex('my custom index name');
 *
 * @param {Object|string} index name or index specification
 * @return {Schema} the Schema instance
 * @api public
 */

Schema.prototype.removeIndex = function removeIndex(index) {
  if (arguments.length > 1) {
    throw new Error('removeIndex() takes only 1 argument');
  }

  if (typeof index !== 'object' && typeof index !== 'string') {
    throw new Error('removeIndex() may only take either an object or a string as an argument');
  }

  if (typeof index === 'object') {
    for (let i = this._indexes.length - 1; i >= 0; --i) {
      if (isIndexSpecEqual(this._indexes[i][0], index)) {
        this._indexes.splice(i, 1);
      }
    }
  } else {
    for (let i = this._indexes.length - 1; i >= 0; --i) {
      if (this._indexes[i][1] != null && this._indexes[i][1].name === index) {
        this._indexes.splice(i, 1);
      }
    }
  }

  return this;
};

/**
 * Remove all indexes from this schema.
 *
 * clearIndexes only removes indexes from your schema object. Does **not** affect the indexes
 * in MongoDB.
 *
 * #### Example:
 *
 *     const ToySchema = new Schema({ name: String, color: String, price: Number });
 *     ToySchema.index({ name: 1 });
 *     ToySchema.index({ color: 1 });
 *
 *     // Remove all indexes on this schema
 *     ToySchema.clearIndexes();
 *
 *     ToySchema.indexes(); // []
 *
 * @return {Schema} the Schema instance
 * @api public
 */

Schema.prototype.clearIndexes = function clearIndexes() {
  this._indexes.length = 0;

  return this;
};

/**
 * Add an [Atlas search index](https://www.mongodb.com/docs/atlas/atlas-search/create-index/) that Mongoose will create using `Model.createSearchIndex()`.
 * This function only works when connected to MongoDB Atlas.
 *
 * #### Example:
 *
 *     const ToySchema = new Schema({ name: String, color: String, price: Number });
 *     ToySchema.searchIndex({ name: 'test', definition: { mappings: { dynamic: true } } });
 *
 * @param {Object} description index options, including `name` and `definition`
 * @param {String} description.name
 * @param {Object} description.definition
 * @return {Schema} the Schema instance
 * @api public
 */

Schema.prototype.searchIndex = function searchIndex(description) {
  this._searchIndexes.push(description);

  return this;
};

/**
 * Reserved document keys.
 *
 * Keys in this object are names that are warned in schema declarations
 * because they have the potential to break Mongoose/ Mongoose plugins functionality. If you create a schema
 * using `new Schema()` with one of these property names, Mongoose will log a warning.
 *
 * - _posts
 * - _pres
 * - collection
  * - emit
 * - errors
 * - get
 * - init
 * - isModified
 * - isNew
 * - listeners
 * - modelName
 * - on
 * - once
 * - populated
 * - prototype
 * - remove
 * - removeListener
 * - save
 * - schema
 * - toObject
 * - validate
 *
 * _NOTE:_ Use of these terms as method names is permitted, but play at your own risk, as they may be existing mongoose document methods you are stomping on.
 *
 *      const schema = new Schema(..);
 *      schema.methods.init = function () {} // potentially breaking
 *
 * @property reserved
 * @memberOf Schema
 * @static
 */

Schema.reserved = Object.create(null);
Schema.prototype.reserved = Schema.reserved;

const reserved = Schema.reserved;
// Core object
reserved['prototype'] =
// EventEmitter
reserved.emit =
reserved.listeners =
reserved.removeListener =

// document properties and functions
reserved.collection =
reserved.errors =
reserved.get =
reserved.init =
reserved.isModified =
reserved.isNew =
reserved.populated =
reserved.remove =
reserved.save =
reserved.toObject =
reserved.validate = 1;
reserved.collection = 1;

/**
 * Gets/sets schema paths.
 *
 * Sets a path (if arity 2)
 * Gets a path (if arity 1)
 *
 * #### Example:
 *
 *     schema.path('name') // returns a SchemaType
 *     schema.path('name', Number) // changes the schemaType of `name` to Number
 *
 * @param {String} path The name of the Path to get / set
 * @param {Object} [obj] The Type to set the path to, if provided the path will be SET, otherwise the path will be GET
 * @api public
 */

Schema.prototype.path = function(path, obj) {
  if (obj === undefined) {
    if (this.paths[path] != null) {
      return this.paths[path];
    }
    // Convert to '.$' to check subpaths re: gh-6405
    const cleanPath = _pathToPositionalSyntax(path);
    let schematype = _getPath(this, path, cleanPath);
    if (schematype != null) {
      return schematype;
    }

    // Look for maps
    const mapPath = getMapPath(this, path);
    if (mapPath != null) {
      return mapPath;
    }

    // Look if a parent of this path is mixed
    schematype = this.hasMixedParent(cleanPath);
    if (schematype != null) {
      return schematype;
    }

    // subpaths?
    return hasNumericSubpathRegex.test(path)
      ? getPositionalPath(this, path, cleanPath)
      : undefined;
  }

  // some path names conflict with document methods
  const firstPieceOfPath = path.split('.')[0];
  if (reserved[firstPieceOfPath] && !this.options.suppressReservedKeysWarning) {
    const errorMessage = `\`${firstPieceOfPath}\` is a reserved schema pathname and may break some functionality. ` +
      'You are allowed to use it, but use at your own risk. ' +
      'To disable this warning pass `suppressReservedKeysWarning` as a schema option.';

    utils.warn(errorMessage);
  }

  if (typeof obj === 'object' && utils.hasUserDefinedProperty(obj, 'ref')) {
    validateRef(obj.ref, path);
  }

  // update the tree
  const subpaths = path.split(/\./);
  const last = subpaths.pop();
  let branch = this.tree;
  let fullPath = '';

  for (const sub of subpaths) {
    if (utils.specialProperties.has(sub)) {
      throw new Error('Cannot set special property `' + sub + '` on a schema');
    }
    fullPath = fullPath += (fullPath.length > 0 ? '.' : '') + sub;
    if (!branch[sub]) {
      this.nested[fullPath] = true;
      branch[sub] = {};
    }
    if (typeof branch[sub] !== 'object') {
      const msg = 'Cannot set nested path `' + path + '`. '
          + 'Parent path `'
          + fullPath
          + '` already set to type ' + branch[sub].name
          + '.';
      throw new Error(msg);
    }
    branch = branch[sub];
  }

  branch[last] = clone(obj);

  this.paths[path] = this.interpretAsType(path, obj, this.options);
  const schemaType = this.paths[path];

  // If overwriting an existing path, make sure to clear the childSchemas
  this.childSchemas = this.childSchemas.filter(childSchema => childSchema.path !== path);

  if (schemaType.$isSchemaMap) {
    // Maps can have arbitrary keys, so `$*` is internal shorthand for "any key"
    // The '$' is to imply this path should never be stored in MongoDB so we
    // can easily build a regexp out of this path, and '*' to imply "any key."
    const mapPath = path + '.$*';

    this.paths[mapPath] = schemaType.$__schemaType;
    this.mapPaths.push(this.paths[mapPath]);
    if (schemaType.$__schemaType.$isSingleNested) {
      this.childSchemas.push({
        schema: schemaType.$__schemaType.schema,
        model: schemaType.$__schemaType.caster,
        path: path
      });
    }
  }

  if (schemaType.$isSingleNested) {
    for (const key of Object.keys(schemaType.schema.paths)) {
      this.singleNestedPaths[path + '.' + key] = schemaType.schema.paths[key];
    }
    for (const key of Object.keys(schemaType.schema.singleNestedPaths)) {
      this.singleNestedPaths[path + '.' + key] =
        schemaType.schema.singleNestedPaths[key];
    }
    for (const key of Object.keys(schemaType.schema.subpaths)) {
      this.singleNestedPaths[path + '.' + key] =
        schemaType.schema.subpaths[key];
    }
    for (const key of Object.keys(schemaType.schema.nested)) {
      this.singleNestedPaths[path + '.' + key] = 'nested';
    }

    Object.defineProperty(schemaType.schema, 'base', {
      configurable: true,
      enumerable: false,
      writable: false,
      value: this.base
    });

    schemaType.caster.base = this.base;
    this.childSchemas.push({
      schema: schemaType.schema,
      model: schemaType.caster,
      path: path
    });
  } else if (schemaType.$isMongooseDocumentArray) {
    Object.defineProperty(schemaType.schema, 'base', {
      configurable: true,
      enumerable: false,
      writable: false,
      value: this.base
    });

    schemaType.casterConstructor.base = this.base;
    this.childSchemas.push({
      schema: schemaType.schema,
      model: schemaType.casterConstructor,
      path: path
    });
  }

  if (schemaType.$isMongooseArray && schemaType.caster instanceof SchemaType) {
    let arrayPath = path;
    let _schemaType = schemaType;

    const toAdd = [];
    while (_schemaType.$isMongooseArray) {
      arrayPath = arrayPath + '.$';

      // Skip arrays of document arrays
      if (_schemaType.$isMongooseDocumentArray) {
        _schemaType.$embeddedSchemaType._arrayPath = arrayPath;
        _schemaType.$embeddedSchemaType._arrayParentPath = path;
        _schemaType = _schemaType.$embeddedSchemaType;
      } else {
        _schemaType.caster._arrayPath = arrayPath;
        _schemaType.caster._arrayParentPath = path;
        _schemaType = _schemaType.caster;
      }

      this.subpaths[arrayPath] = _schemaType;
    }

    for (const _schemaType of toAdd) {
      this.subpaths[_schemaType.path] = _schemaType;
    }
  }

  if (schemaType.$isMongooseDocumentArray) {
    for (const key of Object.keys(schemaType.schema.paths)) {
      const _schemaType = schemaType.schema.paths[key];
      this.subpaths[path + '.' + key] = _schemaType;
      if (typeof _schemaType === 'object' && _schemaType != null && _schemaType.$parentSchemaDocArray == null) {
        _schemaType.$parentSchemaDocArray = schemaType;
      }
    }
    for (const key of Object.keys(schemaType.schema.subpaths)) {
      const _schemaType = schemaType.schema.subpaths[key];
      this.subpaths[path + '.' + key] = _schemaType;
      if (typeof _schemaType === 'object' && _schemaType != null && _schemaType.$parentSchemaDocArray == null) {
        _schemaType.$parentSchemaDocArray = schemaType;
      }
    }
    for (const key of Object.keys(schemaType.schema.singleNestedPaths)) {
      const _schemaType = schemaType.schema.singleNestedPaths[key];
      this.subpaths[path + '.' + key] = _schemaType;
      if (typeof _schemaType === 'object' && _schemaType != null && _schemaType.$parentSchemaDocArray == null) {
        _schemaType.$parentSchemaDocArray = schemaType;
      }
    }
  }

  return this;
};

/*!
 * ignore
 */

Schema.prototype._gatherChildSchemas = function _gatherChildSchemas() {
  const childSchemas = [];

  for (const path of Object.keys(this.paths)) {
    if (typeof path !== 'string') {
      continue;
    }
    const schematype = this.paths[path];
    if (schematype.$isMongooseDocumentArray || schematype.$isSingleNested) {
      childSchemas.push({
        schema: schematype.schema,
        model: schematype.caster,
        path: path
      });
    } else if (schematype.$isSchemaMap && schematype.$__schemaType.$isSingleNested) {
      childSchemas.push({
        schema: schematype.$__schemaType.schema,
        model: schematype.$__schemaType.caster,
        path: path
      });
    }
  }

  this.childSchemas = childSchemas;
  return childSchemas;
};

/*!
 * ignore
 */

function _getPath(schema, path, cleanPath) {
  if (schema.paths.hasOwnProperty(path)) {
    return schema.paths[path];
  }
  if (schema.subpaths.hasOwnProperty(cleanPath)) {
    const subpath = schema.subpaths[cleanPath];
    if (subpath === 'nested') {
      return undefined;
    }
    return subpath;
  }
  if (schema.singleNestedPaths.hasOwnProperty(cleanPath) && typeof schema.singleNestedPaths[cleanPath] === 'object') {
    const singleNestedPath = schema.singleNestedPaths[cleanPath];
    if (singleNestedPath === 'nested') {
      return undefined;
    }
    return singleNestedPath;
  }

  return null;
}

/*!
 * ignore
 */

function _pathToPositionalSyntax(path) {
  if (!/\.\d+/.test(path)) {
    return path;
  }
  return path.replace(/\.\d+\./g, '.$.').replace(/\.\d+$/, '.$');
}

/*!
 * ignore
 */

function getMapPath(schema, path) {
  if (schema.mapPaths.length === 0) {
    return null;
  }
  for (const val of schema.mapPaths) {
    const _path = val.path;
    const re = new RegExp('^' + _path.replace(/\.\$\*/g, '\\.[^.]+') + '$');
    if (re.test(path)) {
      return schema.paths[_path];
    }
  }

  return null;
}

/**
 * The Mongoose instance this schema is associated with
 *
 * @property base
 * @api private
 */

Object.defineProperty(Schema.prototype, 'base', {
  configurable: true,
  enumerable: false,
  writable: true,
  value: null
});

/**
 * Converts type arguments into Mongoose Types.
 *
 * @param {String} path
 * @param {Object} obj constructor
 * @param {Object} options
 * @api private
 */

Schema.prototype.interpretAsType = function(path, obj, options) {
  if (obj instanceof SchemaType) {
    if (obj.path === path) {
      return obj;
    }
    const clone = obj.clone();
    clone.path = path;
    return clone;
  }


  // If this schema has an associated Mongoose object, use the Mongoose object's
  // copy of SchemaTypes re: gh-7158 gh-6933
  const MongooseTypes = this.base != null ? this.base.Schema.Types : Schema.Types;
  const Types = this.base != null ? this.base.Types : require('./types');

  if (!utils.isPOJO(obj) && !(obj instanceof SchemaTypeOptions)) {
    const constructorName = utils.getFunctionName(obj.constructor);
    if (constructorName !== 'Object') {
      const oldObj = obj;
      obj = {};
      obj[options.typeKey] = oldObj;
    }
  }

  // Get the type making sure to allow keys named "type"
  // and default to mixed if not specified.
  // { type: { type: String, default: 'freshcut' } }
  let type = obj[options.typeKey] && (obj[options.typeKey] instanceof Function || options.typeKey !== 'type' || !obj.type.type)
    ? obj[options.typeKey]
    : {};
  let name;

  if (utils.isPOJO(type) || type === 'mixed') {
    return new MongooseTypes.Mixed(path, obj);
  }

  if (Array.isArray(type) || type === Array || type === 'array' || type === MongooseTypes.Array) {
    // if it was specified through { type } look for `cast`
    let cast = (type === Array || type === 'array')
      ? obj.cast || obj.of
      : type[0];

    // new Schema({ path: [new Schema({ ... })] })
    if (cast && cast.instanceOfSchema) {
      if (!(cast instanceof Schema)) {
        if (this.options._isMerging) {
          cast = new Schema(cast);
        } else {
          throw new TypeError('Schema for array path `' + path +
            '` is from a different copy of the Mongoose module. ' +
            'Please make sure you\'re using the same version ' +
            'of Mongoose everywhere with `npm list mongoose`. If you are still ' +
            'getting this error, please add `new Schema()` around the path: ' +
            `${path}: new Schema(...)`);
        }
      }
      return new MongooseTypes.DocumentArray(path, cast, obj);
    }
    if (cast &&
        cast[options.typeKey] &&
        cast[options.typeKey].instanceOfSchema) {
      if (!(cast[options.typeKey] instanceof Schema)) {
        if (this.options._isMerging) {
          cast[options.typeKey] = new Schema(cast[options.typeKey]);
        } else {
          throw new TypeError('Schema for array path `' + path +
            '` is from a different copy of the Mongoose module. ' +
            'Please make sure you\'re using the same version ' +
            'of Mongoose everywhere with `npm list mongoose`. If you are still ' +
            'getting this error, please add `new Schema()` around the path: ' +
            `${path}: new Schema(...)`);
        }
      }
      return new MongooseTypes.DocumentArray(path, cast[options.typeKey], obj, cast);
    }
    if (typeof cast !== 'undefined') {
      if (Array.isArray(cast) || cast.type === Array || cast.type == 'Array') {
        if (cast && cast.type == 'Array') {
          cast.type = Array;
        }
        return new MongooseTypes.Array(path, this.interpretAsType(path, cast, options), obj);
      }
    }

    // Handle both `new Schema({ arr: [{ subpath: String }] })` and `new Schema({ arr: [{ type: { subpath: string } }] })`
    const castFromTypeKey = (cast != null && cast[options.typeKey] && (options.typeKey !== 'type' || !cast.type.type)) ?
      cast[options.typeKey] :
      cast;
    if (typeof cast === 'string') {
      cast = MongooseTypes[cast.charAt(0).toUpperCase() + cast.substring(1)];
    } else if (utils.isPOJO(castFromTypeKey)) {
      if (Object.keys(castFromTypeKey).length) {
        // The `minimize` and `typeKey` options propagate to child schemas
        // declared inline, like `{ arr: [{ val: { $type: String } }] }`.
        // See gh-3560
        const childSchemaOptions = { minimize: options.minimize };
        if (options.typeKey) {
          childSchemaOptions.typeKey = options.typeKey;
        }
        // propagate 'strict' option to child schema
        if (options.hasOwnProperty('strict')) {
          childSchemaOptions.strict = options.strict;
        }
        if (options.hasOwnProperty('strictQuery')) {
          childSchemaOptions.strictQuery = options.strictQuery;
        }
        if (options.hasOwnProperty('toObject')) {
          childSchemaOptions.toObject = utils.omit(options.toObject, ['transform']);
        }
        if (options.hasOwnProperty('toJSON')) {
          childSchemaOptions.toJSON = utils.omit(options.toJSON, ['transform']);
        }

        if (this._userProvidedOptions.hasOwnProperty('_id')) {
          childSchemaOptions._id = this._userProvidedOptions._id;
        } else if (Schema.Types.DocumentArray.defaultOptions._id != null) {
          childSchemaOptions._id = Schema.Types.DocumentArray.defaultOptions._id;
        }

        const childSchema = new Schema(castFromTypeKey, childSchemaOptions);
        childSchema.$implicitlyCreated = true;
        return new MongooseTypes.DocumentArray(path, childSchema, obj);
      } else {
        // Special case: empty object becomes mixed
        return new MongooseTypes.Array(path, MongooseTypes.Mixed, obj);
      }
    }

    if (cast) {
      type = cast[options.typeKey] && (options.typeKey !== 'type' || !cast.type.type)
        ? cast[options.typeKey]
        : cast;
      if (Array.isArray(type)) {
        return new MongooseTypes.Ar