From 297695791557a37f296f6758317fda2b2331d937 Mon Sep 17 00:00:00 2001
From: Sebastian Markbage <sebastian@calyptus.eu>
Date: Wed, 16 Nov 2022 14:20:40 -0500
Subject: [PATCH] Eagerly initialize an mutable object for instance.refs

This micro-optimization never made sense and less so now that they're rare.

This still initializes the class with a shared immutable object in the
constructor - which is also what createClass() does.

Then we override it during mount. This is done in case someone messes up
the initialization of the super() constructor for example, which was
more common in polyfills.

This change means that if a ref is initialized during the constructor
itself it wouldn't be lazily initialized but that's not user code that
does it, it's React so that shouldn't happen.
---
 packages/react-reconciler/src/ReactChildFiber.new.js     | 7 +------
 packages/react-reconciler/src/ReactChildFiber.old.js     | 7 +------
 .../react-reconciler/src/ReactFiberClassComponent.new.js | 9 +--------
 .../react-reconciler/src/ReactFiberClassComponent.old.js | 9 +--------
 4 files changed, 4 insertions(+), 28 deletions(-)

diff --git a/packages/react-reconciler/src/ReactChildFiber.new.js b/packages/react-reconciler/src/ReactChildFiber.new.js
index 07cacc0dbbf8f..6a984baec0c22 100644
--- a/packages/react-reconciler/src/ReactChildFiber.new.js
+++ b/packages/react-reconciler/src/ReactChildFiber.new.js
@@ -39,7 +39,6 @@ import {
   createFiberFromText,
   createFiberFromPortal,
 } from './ReactFiber.new';
-import {emptyRefsObject} from './ReactFiberClassComponent.new';
 import {isCompatibleFamilyForHotReloading} from './ReactFiberHotReloading.new';
 import {StrictLegacyMode} from './ReactTypeOfMode';
 import {getIsHydrating} from './ReactFiberHydrationContext.new';
@@ -192,11 +191,7 @@ function coerceRef(
         return current.ref;
       }
       const ref = function(value) {
-        let refs = resolvedInst.refs;
-        if (refs === emptyRefsObject) {
-          // This is a lazy pooled frozen object, so we need to initialize.
-          refs = resolvedInst.refs = {};
-        }
+        const refs = resolvedInst.refs;
         if (value === null) {
           delete refs[stringRef];
         } else {
diff --git a/packages/react-reconciler/src/ReactChildFiber.old.js b/packages/react-reconciler/src/ReactChildFiber.old.js
index 7bad30d0d3ce6..8b6d4b8130dbd 100644
--- a/packages/react-reconciler/src/ReactChildFiber.old.js
+++ b/packages/react-reconciler/src/ReactChildFiber.old.js
@@ -39,7 +39,6 @@ import {
   createFiberFromText,
   createFiberFromPortal,
 } from './ReactFiber.old';
-import {emptyRefsObject} from './ReactFiberClassComponent.old';
 import {isCompatibleFamilyForHotReloading} from './ReactFiberHotReloading.old';
 import {StrictLegacyMode} from './ReactTypeOfMode';
 import {getIsHydrating} from './ReactFiberHydrationContext.old';
@@ -192,11 +191,7 @@ function coerceRef(
         return current.ref;
       }
       const ref = function(value) {
-        let refs = resolvedInst.refs;
-        if (refs === emptyRefsObject) {
-          // This is a lazy pooled frozen object, so we need to initialize.
-          refs = resolvedInst.refs = {};
-        }
+        const refs = resolvedInst.refs;
         if (value === null) {
           delete refs[stringRef];
         } else {
diff --git a/packages/react-reconciler/src/ReactFiberClassComponent.new.js b/packages/react-reconciler/src/ReactFiberClassComponent.new.js
index 67352b1ca1867..14524865749d8 100644
--- a/packages/react-reconciler/src/ReactFiberClassComponent.new.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.new.js
@@ -12,7 +12,6 @@ import type {Lanes} from './ReactFiberLane.new';
 import type {UpdateQueue} from './ReactFiberClassUpdateQueue.new';
 import type {Flags} from './ReactFiberFlags';
 
-import * as React from 'react';
 import {
   LayoutStatic,
   Update,
@@ -80,12 +79,6 @@ import {
 
 const fakeInternalInstance = {};
 
-// React.Component uses a shared frozen object by default.
-// We'll use it to determine whether we need to initialize legacy refs.
-export const emptyRefsObject: $FlowFixMe = React.Component
-  ? new React.Component().refs
-  : {};
-
 let didWarnAboutStateAssignmentForComponent;
 let didWarnAboutUninitializedState;
 let didWarnAboutGetSnapshotBeforeUpdateWithoutDidUpdate;
@@ -836,7 +829,7 @@ function mountClassInstance(
   const instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = emptyRefsObject;
+  instance.refs = {};
 
   initializeUpdateQueue(workInProgress);
 
diff --git a/packages/react-reconciler/src/ReactFiberClassComponent.old.js b/packages/react-reconciler/src/ReactFiberClassComponent.old.js
index 78962f3587ac2..295367d7a906b 100644
--- a/packages/react-reconciler/src/ReactFiberClassComponent.old.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.old.js
@@ -12,7 +12,6 @@ import type {Lanes} from './ReactFiberLane.old';
 import type {UpdateQueue} from './ReactFiberClassUpdateQueue.old';
 import type {Flags} from './ReactFiberFlags';
 
-import * as React from 'react';
 import {
   LayoutStatic,
   Update,
@@ -80,12 +79,6 @@ import {
 
 const fakeInternalInstance = {};
 
-// React.Component uses a shared frozen object by default.
-// We'll use it to determine whether we need to initialize legacy refs.
-export const emptyRefsObject: $FlowFixMe = React.Component
-  ? new React.Component().refs
-  : {};
-
 let didWarnAboutStateAssignmentForComponent;
 let didWarnAboutUninitializedState;
 let didWarnAboutGetSnapshotBeforeUpdateWithoutDidUpdate;
@@ -836,7 +829,7 @@ function mountClassInstance(
   const instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = emptyRefsObject;
+  instance.refs = {};
 
   initializeUpdateQueue(workInProgress);