Add tests for type changes

-- Add Utility Type do extract type from Aggregate class
-- Fix ResType type for aggregate hook
-- Add tests for post 'save' and post 'aggregate' hooks

Author: GCastilho

test/types/middleware.test.ts

@@ -32,6 +32,16 @@ schema.post<Aggregate<any>>('aggregate', async function(res: Array<any>) {
   console.log('Pipeline', this.pipeline(), res[0]);
 });
 
+schema.post<Aggregate<ITest>>('aggregate', function(res, next) {
+  expectType<ITest[]>(res);
+  next();
+});
+
+schema.post<Query<ITest, ITest>>('save', function(res, next) {
+  expectType<Query<ITest, ITest>>(res);
+  next();
+});
+
 schema.pre(['save', 'validate'], { query: false, document: true }, async function applyChanges() {
   await Test.findOne({});
 });
@@ -45,6 +55,11 @@ schema.pre('save', function(next) {
   console.log(this.name);
 });
 
+schema.post<ITest>('save', function(res, next) {
+  expectType<ITest>(res);
+  next();
+});
+
 schema.post<ITest>('save', function() {
   console.log(this.name);
 });
@@ -96,4 +111,4 @@ function gh11480(): void {
     expectNotType<any>(this);
     next();
   });
-}
+}

types/aggregate.d.ts

@@ -1,6 +1,9 @@
 declare module 'mongoose' {
   import mongodb = require('mongodb');
 
+  /** Extract generic type from Aggregate class */
+  type AggregateExtract<P> = P extends Aggregate<infer T> ? T : never;
+
   interface AggregateOptions extends
     SessionOption {
     /**

types/index.d.ts

@@ -215,8 +215,8 @@ declare module 'mongoose' {
     post<T = HydratedDocument<DocType, TInstanceMethods>>(method: MongooseDocumentMiddleware | MongooseDocumentMiddleware[] | RegExp, options: SchemaPostOptions, fn: PostMiddlewareFunction<T, T>): this;
     post<T extends Query<any, any>>(method: MongooseQueryMiddleware | MongooseQueryMiddleware[] | string | RegExp, fn: PostMiddlewareFunction<T, T>): this;
     post<T extends Query<any, any>>(method: MongooseQueryMiddleware | MongooseQueryMiddleware[] | string | RegExp, options: SchemaPostOptions, fn: PostMiddlewareFunction<T, T>): this;
-    post<T extends Aggregate<any>>(method: 'aggregate' | RegExp, fn: PostMiddlewareFunction<T, Array<T>>): this;
-    post<T extends Aggregate<any>>(method: 'aggregate' | RegExp, options: SchemaPostOptions, fn: PostMiddlewareFunction<T, Array<T>>): this;
+    post<T extends Aggregate<any>>(method: 'aggregate' | RegExp, fn: PostMiddlewareFunction<T, Array<AggregateExtract<T>>>): this;
+    post<T extends Aggregate<any>>(method: 'aggregate' | RegExp, options: SchemaPostOptions, fn: PostMiddlewareFunction<T, Array<AggregateExtract<T>>>): this;
     post<T = M>(method: 'insertMany' | RegExp, fn: PostMiddlewareFunction<T, T>): this;
     post<T = M>(method: 'insertMany' | RegExp, options: SchemaPostOptions, fn: PostMiddlewareFunction<T, T>): this;