feat(query): add sanitizeProjection method to query for better docs

lib/query.js

@@ -1142,6 +1142,59 @@ Query.prototype.select = function select() {
   throw new TypeError('Invalid select() argument. Must be string or object.');
 };
 
+/**
+ * Sets this query's `sanitizeProjection` option. If set, `sanitizeProjection` does
+ * two things:
+ *
+ * 1. Enforces that projection values are numbers, not strings.
+ * 2. Prevents using `+` syntax to override properties that are deselected by default.
+ *
+ * With `sanitizeProjection()`, you can pass potentially untrusted user data to `.select()`.
+ *
+ * #### Example
+ *
+ *     const userSchema = new Schema({
+ *       name: String,
+ *       password: { type: String, select: false }
+ *     });
+ *     const UserModel = mongoose.model('User', userSchema);
+ *     const { _id } = await UserModel.create({ name: 'John', password: 'secret' })
+ *
+ *     // The MongoDB server has special handling for string values that start with '$'
+ *     // in projections, which can lead to unexpected leaking of sensitive data.
+ *     let doc = await UserModel.findOne().select({ name: '$password' });
+ *     doc.name; // 'secret'
+ *     doc.password; // undefined
+ *
+ *     // With `sanitizeProjection`, Mongoose forces all projection values to be numbers
+ *     doc = await UserModel.findOne().sanitizeProjection(true).select({ name: '$password' });
+ *     doc.name; // 'John'
+ *     doc.password; // undefined
+ *
+ *     // By default, Mongoose supports projecting in `password` using `+password`
+ *     doc = await UserModel.findOne().select('+password');
+ *     doc.password; // 'secret'
+ *
+ *     // With `sanitizeProjection`, Mongoose prevents projecting in `password` and other
+ *     // fields that have `select: false` in the schema.
+ *     doc = await UserModel.findOne().sanitizeProjection(true).select('+password');
+ *     doc.password; // undefined
+ *
+ * @method sanitizeProjection
+ * @memberOf Query
+ * @instance
+ * @param {Boolean} value
+ * @return {Query} this
+ * @see sanitizeProjection https://thecodebarbarian.com/whats-new-in-mongoose-5-13-sanitizeprojection.html
+ * @api public
+ */
+
+Query.prototype.sanitizeProjection = function sanitizeProjection(value) {
+  this._mongooseOptions.sanitizeProjection = value;
+
+  return this;
+};
+
 /**
  * Determines the MongoDB nodes from which to read.
  *

types/query.d.ts

@@ -716,6 +716,11 @@ declare module 'mongoose' {
       options?: QueryOptions<DocType> | null
     ): QueryWithHelpers<any, DocType, THelpers, RawDocType, 'replaceOne', TInstanceMethods>;
 
+    /**
+     * Sets this query's `sanitizeProjection` option. With `sanitizeProjection()`, you can pass potentially untrusted user data to `.select()`.
+     */
+    sanitizeProjection(value: boolean): this;
+
     /** Specifies which document fields to include or exclude (also known as the query "projection") */
     select<RawDocTypeOverride extends { [P in keyof RawDocType]?: any } = {}>(
       arg: string | string[] | Record<string, number | boolean | string | object>