From 4740929950b7043da51a0b717c9e6e1116791f02 Mon Sep 17 00:00:00 2001
From: Joel Walker <joel@walker9.net>
Date: Fri, 29 Dec 2023 15:41:40 -0800
Subject: [PATCH] fix: `Object.groupBy` return type should be a partial
 (#21680)

Signed-off-by: Joel Walker <joelwalker1995@gmail.com>
---
 cli/tests/unit/globals_test.ts     | 6 ++++++
 cli/tsc/dts/lib.esnext.object.d.ts | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/cli/tests/unit/globals_test.ts b/cli/tests/unit/globals_test.ts
index 9f7f776447..1bb5b50f0a 100644
--- a/cli/tests/unit/globals_test.ts
+++ b/cli/tests/unit/globals_test.ts
@@ -196,6 +196,12 @@ Deno.test(function objectGroupBy() {
   });
 });
 
+Deno.test(function objectGroupByEmpty() {
+  const empty: string[] = [];
+  const result = Object.groupBy(empty, () => "abc");
+  assertEquals(result.abc, undefined);
+});
+
 // Taken from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/groupBy#examples
 Deno.test(function mapGroupBy() {
   const inventory = [
diff --git a/cli/tsc/dts/lib.esnext.object.d.ts b/cli/tsc/dts/lib.esnext.object.d.ts
index 130f2fc9fa..3440d8d0dd 100644
--- a/cli/tsc/dts/lib.esnext.object.d.ts
+++ b/cli/tsc/dts/lib.esnext.object.d.ts
@@ -21,7 +21,7 @@ interface ObjectConstructor {
   groupBy<Item, Key extends PropertyKey>(
     items: Iterable<Item>,
     keySelector: (item: Item, index: number) => Key,
-  ): Record<Key, Item[]>;
+  ): Partial<Record<Key, Item[]>>;
 }
 
 interface MapConstructor {