From 374ac503d7824ecbd6f2c813e2fcefaec890dad1 Mon Sep 17 00:00:00 2001
From: Hitko Development <development@hitko.si>
Date: Tue, 5 May 2020 12:31:12 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=A4=96=20Merge=20PR=20#44476=20[mongodb]?=
 =?UTF-8?q?=20fix=20return=20array=20type=20for=20distinct=20by=20@HitkoDe?=
 =?UTF-8?q?v?=
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---
 types/mongodb/index.d.ts                  | 11 +++++++----
 types/mongodb/test/collection/distinct.ts |  5 +++++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/types/mongodb/index.d.ts b/types/mongodb/index.d.ts
index 6da8649f46..cac5a50870 100644
--- a/types/mongodb/index.d.ts
+++ b/types/mongodb/index.d.ts
@@ -29,6 +29,7 @@
 //                 Richard Bateman <https://github.com/taxilian>
 //                 Igor Strebezhev <https://github.com/xamgore>
 //                 Valentin Agachi <https://github.com/avaly>
+//                 HitkoDev <https://github.com/HitkoDev>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // Minimum TypeScript Version: 3.2
 
@@ -44,6 +45,8 @@ import { checkServerIdentity } from 'tls';
 // We can use TypeScript Omit once minimum required TypeScript Version is above 3.5
 type Omit<T, K> = Pick<T, Exclude<keyof T, K>>;
 
+type FlattenIfArray<T> = T extends Array<infer R> ? R : T;
+
 export function connect(uri: string, options?: MongoClientOptions): Promise<MongoClient>;
 export function connect(uri: string, callback: MongoCallback<MongoClient>): void;
 export function connect(uri: string, options: MongoClientOptions, callback: MongoCallback<MongoClient>): void;
@@ -1012,10 +1015,10 @@ export interface Collection<TSchema extends { [key: string]: any } = DefaultSche
     deleteOne(filter: FilterQuery<TSchema>, options?: CommonOptions & { bypassDocumentValidation?: boolean }): Promise<DeleteWriteOpResultObject>;
     deleteOne(filter: FilterQuery<TSchema>, options: CommonOptions & { bypassDocumentValidation?: boolean }, callback: MongoCallback<DeleteWriteOpResultObject>): void;
     /** http://mongodb.github.io/node-mongodb-native/3.1/api/Collection.html#distinct */
-    distinct<Key extends keyof WithId<TSchema>>(key: Key, callback: MongoCallback<Array<WithId<TSchema>[Key]>>): void;
-    distinct<Key extends keyof WithId<TSchema>>(key: Key, query: FilterQuery<TSchema>, callback: MongoCallback<Array<WithId<TSchema>[Key]>>): void;
-    distinct<Key extends keyof WithId<TSchema>>(key: Key, query?: FilterQuery<TSchema>, options?: MongoDistinctPreferences): Promise<Array<WithId<TSchema>[Key]>>;
-    distinct<Key extends keyof WithId<TSchema>>(key: Key, query: FilterQuery<TSchema>, options: MongoDistinctPreferences, callback: MongoCallback<Array<WithId<TSchema>[Key]>>): void;
+    distinct<Key extends keyof WithId<TSchema>>(key: Key, callback: MongoCallback<Array<FlattenIfArray<WithId<TSchema>[Key]>>>): void;
+    distinct<Key extends keyof WithId<TSchema>>(key: Key, query: FilterQuery<TSchema>, callback: MongoCallback<Array<FlattenIfArray<WithId<TSchema>[Key]>>>): void;
+    distinct<Key extends keyof WithId<TSchema>>(key: Key, query?: FilterQuery<TSchema>, options?: MongoDistinctPreferences): Promise<Array<FlattenIfArray<WithId<TSchema>[Key]>>>;
+    distinct<Key extends keyof WithId<TSchema>>(key: Key, query: FilterQuery<TSchema>, options: MongoDistinctPreferences, callback: MongoCallback<Array<FlattenIfArray<WithId<TSchema>[Key]>>>): void;
     distinct(key: string, callback: MongoCallback<any[]>): void;
     distinct(key: string, query: FilterQuery<TSchema>, callback: MongoCallback<any[]>): void;
     distinct(key: string, query?: FilterQuery<TSchema>, options?: MongoDistinctPreferences): Promise<any[]>;
diff --git a/types/mongodb/test/collection/distinct.ts b/types/mongodb/test/collection/distinct.ts
index 5b4cf6bffa..9a2b894949 100644
--- a/types/mongodb/test/collection/distinct.ts
+++ b/types/mongodb/test/collection/distinct.ts
@@ -6,6 +6,7 @@ async function run() {
   interface Collection {
     foo: number;
     nested: { num: number; };
+    array: string[];
     test: string;
   }
 
@@ -35,4 +36,8 @@ async function run() {
   collection.distinct('nested.num'); // $ExpectType Promise<any[]>
   collection.distinct('nested.num', { foo: 1 }); // $ExpectType Promise<any[]>
   collection.distinct('nested.num', { foo: 1 }, { maxTimeMS: 400 }); // $ExpectType Promise<any[]>
+
+  collection.distinct('array'); // $ExpectType Promise<string[]>
+  collection.distinct('array', { foo: 1 }); // $ExpectType Promise<string[]>
+  collection.distinct('array', { foo: 1 }, { maxTimeMS: 400 }); // $ExpectType Promise<string[]>
 }