From f50ff357cf45d5cbda8d5a99c247e33b0477e936 Mon Sep 17 00:00:00 2001
From: Brian Vaughn <bvaughn@fb.com>
Date: Fri, 17 Sep 2021 12:53:07 -0400
Subject: [PATCH] DevTools: Fix memory leak via alternate Fiber pointer
 (#22346)

---
 packages/react-devtools-shared/src/backend/renderer.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/react-devtools-shared/src/backend/renderer.js b/packages/react-devtools-shared/src/backend/renderer.js
index 3f03315fa5ce7..1cfcaaa6a866b 100644
--- a/packages/react-devtools-shared/src/backend/renderer.js
+++ b/packages/react-devtools-shared/src/backend/renderer.js
@@ -1140,6 +1140,13 @@ export function attach(
 
     untrackFibersSet.add(fiber);
 
+    // React may detach alternate pointers during unmount;
+    // Since our untracking code is async, we should explicily track the pending alternate here as well.
+    const alternate = fiber.alternate;
+    if (alternate !== null) {
+      untrackFibersSet.add(alternate);
+    }
+
     if (untrackFibersTimeoutID === null) {
       untrackFibersTimeoutID = setTimeout(untrackFibers, 1000);
     }