From 04496306123c46730b46accb2cd6239531e51fef Mon Sep 17 00:00:00 2001
From: Eric Rozell <ericroz@meta.com>
Date: Wed, 9 Oct 2024 05:25:10 -0700
Subject: [PATCH] Resolve Paper leak on Android (#46896)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46896

On Android Paper UIManager, when calling `ReactRootView.unmountReactApplication`, the ReactRootView tag is unset [here](https://github.com/facebook/react-native/blob/main/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java#L926), before the round trip unmount operation to JS makes it's way back to a `dropView` call on `NativeViewHierarchyManager`.

In practice, this means that legacy architecture apps that unmount surfaces via `ReactRootView.unmountReactApplication` leak references to Views, and the "finalization" step (`onDropViewInstance`) is not universally called.

This is an attempt to fix the issue by skipping the `clearReactRoot` step on Paper, instead waiting for the round trip `UIManager.removeRootView` call.

## Changelog

[Android][Fixed] Fix issue where `onDropViewInstance` cleanup was not being handled after `ReactRootView.unmountReactApplication`

Reviewed By: javache

Differential Revision: D64054042

fbshipit-source-id: b8b8c237796674ca23a332e57a1bf2e07ab5af13
---
 .../main/java/com/facebook/react/ReactInstanceManager.java    | 4 ++--
 .../facebook/react/uimanager/NativeViewHierarchyManager.java  | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
index 939f12c91ef..bc190d6f6e6 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
@@ -1391,14 +1391,14 @@ public class ReactInstanceManager {
             new RuntimeException(
                 "detachRootViewFromInstance called with ReactRootView with invalid id"));
       }
+
+      clearReactRoot(reactRoot);
     } else {
       reactContext
           .getCatalystInstance()
           .getJSModule(AppRegistry.class)
           .unmountApplicationComponentAtRootTag(reactRoot.getRootViewTag());
     }
-
-    clearReactRoot(reactRoot);
   }
 
   @ThreadConfined(UI)
diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/NativeViewHierarchyManager.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/NativeViewHierarchyManager.java
index 34ccb6f05bd..b5b1151317e 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/NativeViewHierarchyManager.java
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/NativeViewHierarchyManager.java
@@ -674,6 +674,9 @@ public class NativeViewHierarchyManager {
     View rootView = mTagsToViews.get(rootViewTag);
     dropView(rootView);
     mRootTags.delete(rootViewTag);
+    if (rootView != null) {
+      rootView.setId(View.NO_ID);
+    }
   }
 
   /**