From 441024318c2286f75979292577ef7e25fbb2cffb Mon Sep 17 00:00:00 2001
From: Sathya Gunsasekaran <gsathya.ceg@gmail.com>
Date: Fri, 12 Apr 2024 15:32:12 +0100
Subject: [PATCH] [polyfill] Add sentinel to array

To make the polyfill work well with devtools, we add this sentinel.

Devtools will look for this sentinel before adding the Forget badge.

ghstack-source-id: d246040f67da48fa46f818753c8bf26dff56f390
Pull Request resolved: https://github.com/facebook/react-forget/pull/2847
---
 compiler/packages/react-forget-runtime/src/index.ts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/compiler/packages/react-forget-runtime/src/index.ts b/compiler/packages/react-forget-runtime/src/index.ts
index 8c9658e6fe..415b86aa15 100644
--- a/compiler/packages/react-forget-runtime/src/index.ts
+++ b/compiler/packages/react-forget-runtime/src/index.ts
@@ -28,6 +28,10 @@ export function unstable_useMemoCache(size: number) {
     for (let ii = 0; ii < size; ii++) {
       $[ii] = $empty;
     }
+    // This symbol is added to tell the react devtools that this array is from
+    // useMemoCache.
+    // @ts-ignore
+    $[$empty] = true;
     return $;
   })[0];
 }