From a299a0bf30decef451b4fd3218ea2c9719fd962e Mon Sep 17 00:00:00 2001
From: Eric Adum <eric.adum@mongodb.com>
Date: Wed, 1 Sep 2021 11:21:00 -0400
Subject: [PATCH] fix(NODE-3567): correct typing on aggregation out helper
 (#2967)

---
 src/cursor/aggregation_cursor.ts | 4 ++--
 test/types/mongodb.test-d.ts     | 6 +++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/cursor/aggregation_cursor.ts b/src/cursor/aggregation_cursor.ts
index 2f293c852e..6efae2035c 100644
--- a/src/cursor/aggregation_cursor.ts
+++ b/src/cursor/aggregation_cursor.ts
@@ -120,8 +120,8 @@ export class AggregationCursor<TSchema = Document> extends AbstractCursor<TSchem
     return this;
   }
 
-  /** Add a out stage to the aggregation pipeline */
-  out($out: number): this {
+  /** Add an out stage to the aggregation pipeline */
+  out($out: string): this {
     assertUninitialized(this);
     this[kPipeline].push({ $out });
     return this;
diff --git a/test/types/mongodb.test-d.ts b/test/types/mongodb.test-d.ts
index cbab6a773e..c84f100b4f 100644
--- a/test/types/mongodb.test-d.ts
+++ b/test/types/mongodb.test-d.ts
@@ -1,4 +1,4 @@
-import { expectType, expectDeprecated } from 'tsd';
+import { expectType, expectDeprecated, expectError } from 'tsd';
 import { MongoClient } from '../../src/mongo_client';
 import { Collection } from '../../src/collection';
 import { AggregationCursor } from '../../src/cursor/aggregation_cursor';
@@ -35,3 +35,7 @@ const composedMap = mappedAgg.map<string>(x => x.toString());
 expectType<AggregationCursor<string>>(composedMap);
 expectType<string | null>(await composedMap.next());
 expectType<string[]>(await composedMap.toArray());
+
+const builtCursor = coll.aggregate();
+expectType<AggregationCursor<Document>>(builtCursor.out('string')); // should allow string values for the out helper
+expectError(builtCursor.out(1)); // should error on non-string values