Support writing to this.refs from userspace (#28867)

Previously, the `refs` property of a class component instance was
read-only by user code — only React could write to it, and until/unless
a string ref was used, it pointed to a shared empty object that was
frozen in dev to prevent userspace mutations.

Because string refs are deprecated, we want users to be able to codemod
all their string refs to callback refs. The safest way to do this is to
output a callback ref that assigns to `this.refs`.

So to support this, we need to make `this.refs` writable by userspace.

DiffTrain build for commit https://github.com/facebook/react/commit/ea24427d16f3ac9b0f3bb45cdc7919ac208130c9.

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react-test-renderer/cjs/ReactTestRenderer-dev.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<f80067582f8d263400103116af004cc1>>
+ * @generated SignedSource<<1af14f0d0942bd1e022dac734e776b15>>
  */
 
 "use strict";
@@ -12589,7 +12589,6 @@ if (__DEV__) {
       var instance = workInProgress.stateNode;
       instance.props = newProps;
       instance.state = workInProgress.memoizedState;
-      instance.refs = {};
       initializeUpdateQueue(workInProgress);
       var contextType = ctor.contextType;
 
@@ -26673,7 +26672,7 @@ if (__DEV__) {
       return root;
     }
 
-    var ReactVersion = "19.0.0-canary-a47ffde4";
+    var ReactVersion = "19.0.0-canary-4a670971";
 
     /*
      * The `'' + value` pattern (used in perf-sensitive code) throws for Symbol

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react-test-renderer/cjs/ReactTestRenderer-prod.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<f3eb1768c908f25292e8f079ec672f53>>
+ * @generated SignedSource<<c7247ab9f63052e5a0750fdb7aaf6996>>
  */
 
 "use strict";
@@ -3426,7 +3426,6 @@ function mountClassInstance(workInProgress, ctor, newProps, renderLanes) {
   var instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = {};
   initializeUpdateQueue(workInProgress);
   var contextType = ctor.contextType;
   "object" === typeof contextType && null !== contextType
@@ -9144,7 +9143,7 @@ var devToolsConfig$jscomp$inline_1019 = {
     throw Error("TestRenderer does not support findFiberByHostInstance()");
   },
   bundleType: 0,
-  version: "19.0.0-canary-7a48fce4",
+  version: "19.0.0-canary-3c5c4140",
   rendererPackageName: "react-test-renderer"
 };
 var internals$jscomp$inline_1238 = {
@@ -9175,7 +9174,7 @@ var internals$jscomp$inline_1238 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "19.0.0-canary-7a48fce4"
+  reconcilerVersion: "19.0.0-canary-3c5c4140"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
   var hook$jscomp$inline_1239 = __REACT_DEVTOOLS_GLOBAL_HOOK__;

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react-test-renderer/cjs/ReactTestRenderer-profiling.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<9206ca0f6781a4c840d6d393f26b3429>>
+ * @generated SignedSource<<2efa00521669a237ba088981baf581b8>>
  */
 
 "use strict";
@@ -3584,7 +3584,6 @@ function mountClassInstance(workInProgress, ctor, newProps, renderLanes) {
   var instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = {};
   initializeUpdateQueue(workInProgress);
   var contextType = ctor.contextType;
   "object" === typeof contextType && null !== contextType
@@ -9760,7 +9759,7 @@ var devToolsConfig$jscomp$inline_1101 = {
     throw Error("TestRenderer does not support findFiberByHostInstance()");
   },
   bundleType: 0,
-  version: "19.0.0-canary-39a6938a",
+  version: "19.0.0-canary-dec118c3",
   rendererPackageName: "react-test-renderer"
 };
 (function (internals) {
@@ -9804,7 +9803,7 @@ var devToolsConfig$jscomp$inline_1101 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "19.0.0-canary-39a6938a"
+  reconcilerVersion: "19.0.0-canary-dec118c3"
 });
 exports._Scheduler = Scheduler;
 exports.act = act;

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/cjs/React-dev.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<150980e4b77b12c241c9997159b4f67a>>
+ * @generated SignedSource<<df40c362ab4858d0f1f3b69d7d7eb4ad>>
  */
 
 "use strict";
@@ -26,7 +26,7 @@ if (__DEV__) {
     }
     var dynamicFlagsUntyped = require("ReactNativeInternalFeatureFlags");
 
-    var ReactVersion = "19.0.0-canary-a13a0c2f";
+    var ReactVersion = "19.0.0-canary-d59b7713";
 
     // ATTENTION
     // When adding new symbols to this file,
@@ -299,20 +299,14 @@ if (__DEV__) {
 
     var assign = Object.assign;
 
-    var emptyObject = {};
-
-    {
-      Object.freeze(emptyObject);
-    }
     /**
      * Base class helpers for the updating state of a component.
      */
 
     function Component(props, context, updater) {
       this.props = props;
-      this.context = context; // If a component has string refs, we will assign a different object later.
-
-      this.refs = emptyObject; // We initialize the default updater but the real one gets injected by the
+      this.context = context;
+      this.refs = {}; // We initialize the default updater but the real one gets injected by the
       // renderer.
 
       this.updater = updater || ReactNoopUpdateQueue;
@@ -429,7 +423,7 @@ if (__DEV__) {
       this.props = props;
       this.context = context; // If a component has string refs, we will assign a different object later.
 
-      this.refs = emptyObject;
+      this.refs = {};
       this.updater = updater || ReactNoopUpdateQueue;
     }
 

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/cjs/React-prod.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<00252b7815c38ef0d757b44717a43f7d>>
+ * @generated SignedSource<<4623f2323ff9fe23a59f41063e37036d>>
  */
 
 "use strict";
@@ -46,12 +46,11 @@ var ReactNoopUpdateQueue = {
     enqueueReplaceState: function () {},
     enqueueSetState: function () {}
   },
-  assign = Object.assign,
-  emptyObject = {};
+  assign = Object.assign;
 function Component(props, context, updater) {
   this.props = props;
   this.context = context;
-  this.refs = emptyObject;
+  this.refs = {};
   this.updater = updater || ReactNoopUpdateQueue;
 }
 Component.prototype.isReactComponent = {};
@@ -74,7 +73,7 @@ ComponentDummy.prototype = Component.prototype;
 function PureComponent(props, context, updater) {
   this.props = props;
   this.context = context;
-  this.refs = emptyObject;
+  this.refs = {};
   this.updater = updater || ReactNoopUpdateQueue;
 }
 var pureComponentPrototype = (PureComponent.prototype = new ComponentDummy());
@@ -679,4 +678,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.0.0-canary-3277b133";
+exports.version = "19.0.0-canary-43e619b6";

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/cjs/React-profiling.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<9fd3393509037fbe670735ccea6d8cca>>
+ * @generated SignedSource<<6bf80ec383f6cf4c2e8d203cf6a830b0>>
  */
 
 "use strict";
@@ -50,12 +50,11 @@ var ReactNoopUpdateQueue = {
     enqueueReplaceState: function () {},
     enqueueSetState: function () {}
   },
-  assign = Object.assign,
-  emptyObject = {};
+  assign = Object.assign;
 function Component(props, context, updater) {
   this.props = props;
   this.context = context;
-  this.refs = emptyObject;
+  this.refs = {};
   this.updater = updater || ReactNoopUpdateQueue;
 }
 Component.prototype.isReactComponent = {};
@@ -78,7 +77,7 @@ ComponentDummy.prototype = Component.prototype;
 function PureComponent(props, context, updater) {
   this.props = props;
   this.context = context;
-  this.refs = emptyObject;
+  this.refs = {};
   this.updater = updater || ReactNoopUpdateQueue;
 }
 var pureComponentPrototype = (PureComponent.prototype = new ComponentDummy());
@@ -683,7 +682,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.0.0-canary-52747c26";
+exports.version = "19.0.0-canary-c3e8564d";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/REVISION

@@ -1 +1 @@
-0061ca6cf47c5124d2ebe708481fb03da9e8e267
+ea24427d16f3ac9b0f3bb45cdc7919ac208130c9

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/implementations/ReactFabric-dev.fb.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<84d884f07a1d5851f53652012b257860>>
+ * @generated SignedSource<<69452b089b0732ebffeaf4ae565a8ac2>>
  */
 
 "use strict";
@@ -16131,7 +16131,6 @@ to return true:wantsResponderID|                            |
       var instance = workInProgress.stateNode;
       instance.props = newProps;
       instance.state = workInProgress.memoizedState;
-      instance.refs = {};
       initializeUpdateQueue(workInProgress);
       var contextType = ctor.contextType;
 
@@ -30296,7 +30295,7 @@ to return true:wantsResponderID|                            |
       return root;
     }
 
-    var ReactVersion = "19.0.0-canary-adfb7d73";
+    var ReactVersion = "19.0.0-canary-385c1224";
 
     /*
      * The `'' + value` pattern (used in perf-sensitive code) throws for Symbol

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/implementations/ReactFabric-prod.fb.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<d42756695dd6c4c7a24ede54b6a5902a>>
+ * @generated SignedSource<<13b0be8da9b49fcd1f29069f699207ea>>
  */
 
 "use strict";
@@ -4995,7 +4995,6 @@ function mountClassInstance(workInProgress, ctor, newProps, renderLanes) {
   var instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = {};
   initializeUpdateQueue(workInProgress);
   var contextType = ctor.contextType;
   "object" === typeof contextType && null !== contextType
@@ -10602,7 +10601,7 @@ var roots = new Map(),
   devToolsConfig$jscomp$inline_1099 = {
     findFiberByHostInstance: getInstanceFromNode,
     bundleType: 0,
-    version: "19.0.0-canary-7f7baf16",
+    version: "19.0.0-canary-7feb98a8",
     rendererPackageName: "react-native-renderer",
     rendererConfig: {
       getInspectorDataForInstance: getInspectorDataForInstance,
@@ -10645,7 +10644,7 @@ var internals$jscomp$inline_1366 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "19.0.0-canary-7f7baf16"
+  reconcilerVersion: "19.0.0-canary-7feb98a8"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
   var hook$jscomp$inline_1367 = __REACT_DEVTOOLS_GLOBAL_HOOK__;

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/implementations/ReactFabric-profiling.fb.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<64acec7be24561ecbf6d2eaf55e55d0a>>
+ * @generated SignedSource<<dd792dd5b38efe98d74676e597f14301>>
  */
 
 "use strict";
@@ -5187,7 +5187,6 @@ function mountClassInstance(workInProgress, ctor, newProps, renderLanes) {
   var instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = {};
   initializeUpdateQueue(workInProgress);
   var contextType = ctor.contextType;
   "object" === typeof contextType && null !== contextType
@@ -11307,7 +11306,7 @@ var roots = new Map(),
   devToolsConfig$jscomp$inline_1179 = {
     findFiberByHostInstance: getInstanceFromNode,
     bundleType: 0,
-    version: "19.0.0-canary-ef6bcf29",
+    version: "19.0.0-canary-e320aa3b",
     rendererPackageName: "react-native-renderer",
     rendererConfig: {
       getInspectorDataForInstance: getInspectorDataForInstance,
@@ -11363,7 +11362,7 @@ var roots = new Map(),
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "19.0.0-canary-ef6bcf29"
+  reconcilerVersion: "19.0.0-canary-e320aa3b"
 });
 exports.createPortal = function (children, containerTag) {
   return createPortal$1(

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/implementations/ReactNativeRenderer-dev.fb.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<cda44a9b6dde6c0bc692dd0a256b0422>>
+ * @generated SignedSource<<a9c02652daf34108f64b03d290ef9434>>
  */
 
 "use strict";
@@ -16402,7 +16402,6 @@ to return true:wantsResponderID|                            |
       var instance = workInProgress.stateNode;
       instance.props = newProps;
       instance.state = workInProgress.memoizedState;
-      instance.refs = {};
       initializeUpdateQueue(workInProgress);
       var contextType = ctor.contextType;
 
@@ -30750,7 +30749,7 @@ to return true:wantsResponderID|                            |
       return root;
     }
 
-    var ReactVersion = "19.0.0-canary-ad24d706";
+    var ReactVersion = "19.0.0-canary-22e6f306";
 
     /*
      * The `'' + value` pattern (used in perf-sensitive code) throws for Symbol

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/implementations/ReactNativeRenderer-prod.fb.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<40e33e67d4c6fd0373352fbe892a02dc>>
+ * @generated SignedSource<<b7840bcf19abcdf73d5013da4e79dca5>>
  */
 
 "use strict";
@@ -5048,7 +5048,6 @@ function mountClassInstance(workInProgress, ctor, newProps, renderLanes) {
   var instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = {};
   initializeUpdateQueue(workInProgress);
   var contextType = ctor.contextType;
   "object" === typeof contextType && null !== contextType
@@ -10824,7 +10823,7 @@ var roots = new Map(),
   devToolsConfig$jscomp$inline_1168 = {
     findFiberByHostInstance: getInstanceFromTag,
     bundleType: 0,
-    version: "19.0.0-canary-7fc44ecb",
+    version: "19.0.0-canary-21664510",
     rendererPackageName: "react-native-renderer",
     rendererConfig: {
       getInspectorDataForInstance: getInspectorDataForInstance,
@@ -10867,7 +10866,7 @@ var internals$jscomp$inline_1452 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "19.0.0-canary-7fc44ecb"
+  reconcilerVersion: "19.0.0-canary-21664510"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
   var hook$jscomp$inline_1453 = __REACT_DEVTOOLS_GLOBAL_HOOK__;

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/implementations/ReactNativeRenderer-profiling.fb.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<e4cc143cf5b6c40986732f7c31042c95>>
+ * @generated SignedSource<<133502ac169bad393685ab94706b7e59>>
  */
 
 "use strict";
@@ -5240,7 +5240,6 @@ function mountClassInstance(workInProgress, ctor, newProps, renderLanes) {
   var instance = workInProgress.stateNode;
   instance.props = newProps;
   instance.state = workInProgress.memoizedState;
-  instance.refs = {};
   initializeUpdateQueue(workInProgress);
   var contextType = ctor.contextType;
   "object" === typeof contextType && null !== contextType
@@ -11530,7 +11529,7 @@ var roots = new Map(),
   devToolsConfig$jscomp$inline_1248 = {
     findFiberByHostInstance: getInstanceFromTag,
     bundleType: 0,
-    version: "19.0.0-canary-b6bdb4e2",
+    version: "19.0.0-canary-b8a8669d",
     rendererPackageName: "react-native-renderer",
     rendererConfig: {
       getInspectorDataForInstance: getInspectorDataForInstance,
@@ -11586,7 +11585,7 @@ var roots = new Map(),
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "19.0.0-canary-b6bdb4e2"
+  reconcilerVersion: "19.0.0-canary-b8a8669d"
 });
 exports.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED = {
   computeComponentStackForErrorReporting: function (reactTag) {