feat(aggregate): add Aggregate.prototype.finally() to be consistent…

… with Promise API for TypeScript

lib/aggregate.js

@@ -1094,7 +1094,7 @@ Aggregate.prototype.then = function(resolve, reject) {
 };
 
 /**
- * Executes the query returning a `Promise` which will be
+ * Executes the aggregation returning a `Promise` which will be
  * resolved with either the doc(s) or rejected with the error.
  * Like [`.then()`](https://mongoosejs.com/docs/api/query.html#Query.prototype.then), but only takes a rejection handler.
  * Compatible with `await`.
@@ -1108,6 +1108,21 @@ Aggregate.prototype.catch = function(reject) {
   return this.exec().then(null, reject);
 };
 
+/**
+ * Executes the aggregate returning a `Promise` which will be
+ * resolved with `.finally()` chained.
+ *
+ * More about [Promise `finally()` in JavaScript](https://thecodebarbarian.com/using-promise-finally-in-node-js.html).
+ *
+ * @param {Function} [onFinally]
+ * @return {Promise}
+ * @api public
+ */
+
+Aggregate.prototype.finally = function(onFinally) {
+  return this.exec().finally(onFinally);
+};
+
 /**
  * Returns an asyncIterator for use with [`for/await/of` loops](https://thecodebarbarian.com/getting-started-with-async-iterators-in-node-js)
  * You do not need to call this function explicitly, the JavaScript runtime

types/aggregate.d.ts

@@ -16,6 +16,9 @@ declare module 'mongoose' {
      */
     [Symbol.asyncIterator](): AsyncIterableIterator<Unpacked<ResultType>>;
 
+    // Returns a string representation of this aggregation.
+    [Symbol.toStringTag]: string;
+
     options: AggregateOptions;
 
     /**
@@ -73,6 +76,12 @@ declare module 'mongoose' {
     /** Appends a new $fill operator to this aggregate pipeline */
     fill(arg: PipelineStage.Fill['$fill']): this;
 
+    /**
+     * Executes the aggregation returning a `Promise` which will be
+     * resolved with `.finally()` chained.
+     */
+    finally: Promise<ResultType>['finally'];
+
     /** Appends new custom $graphLookup operator(s) to this aggregate pipeline, performing a recursive search on a collection. */
     graphLookup(options: PipelineStage.GraphLookup['$graphLookup']): this;