Event.NONE/CAPTURING_PHASE/AT_TARGET/BUBBLING_PHASE properties missing configurable: true breaks event-target-shim

[ejkkan]

Description

The new Event implementation in src/private/webapis/dom/events/Event.js (lines 186-231) defines phase constants (NONE, CAPTURING_PHASE, AT_TARGET,
BUBBLING_PHASE) without configurable: true or writable: true.

Since these default to false, the properties become non-configurable. This breaks event-target-shim (used by abort-controller, which is used by fetch()
internally), causing:

"Cannot assign to read-only property 'NONE'"

Fix: Add configurable: true, writable: true to all 8 Object.defineProperty calls.

Steps to reproduce

1. Create a new RN 0.81 app with New Architecture enabled
2. Make any fetch() request (e.g., fetch('https://httpbin.org/get'))
3. Error: "Cannot assign to read-only property 'NONE'"

React Native Version

0.81.5

Affected Platforms

Runtime - Android, Runtime - iOS

Output of npx @react-native-community/cli info

Stacktrace:
  Uncaught Error
  Cannot assign to read-only property 'NONE'

  Call Stack:
  Event
  anonymous
  emit
  anonymous
  emit

Stacktrace or Logs

Stacktrace:
  Uncaught Error
  Cannot assign to read-only property 'NONE'

  Call Stack:
  Event
  anonymous
  emit
  anonymous
  emit

MANDATORY Reproducer

ReproducerNONE

Screenshots and Videos

No response

[hasan4adnan]

I’m also hitting this on React Native 0.81.5 (New Architecture) on both iOS and Android when making a simple fetch() call.
The root cause seems to be how the Event phase constants are defined in src/private/webapis/dom/events/Event.js. The file uses Object.defineProperty without specifying configurable or writable, for example:

Object.defineProperty(Event, 'NONE', { value: 0 });
Object.defineProperty(Event, 'CAPTURING_PHASE', { value: 1 });
Object.defineProperty(Event, 'AT_TARGET', { value: 2 });
Object.defineProperty(Event, 'BUBBLING_PHASE', { value: 3 });
// …and the same pattern for Event.prototype

Per Object.defineProperty semantics, any flags you don’t specify default to false, so these become non-configurable, non-writable data properties. When event-target-shim (pulled in by abort-controller, which is in turn used by fetch) initializes, it attempts to redefine these constants on Event with its own descriptors. Because the properties are non-configurable, that defineProperty call throws, producing:
TypeError: Cannot assign to read-only property 'NONE'
A minimal, backwards-compatible fix is to make these constants configurable and writable in the React Native DOM polyfill so that event-target-shim can safely redefine them:

Object.defineProperty(Event, 'NONE', {
  value: 0,
  configurable: true,
  writable: true,
});

Object.defineProperty(Event, 'CAPTURING_PHASE', {
  value: 1,
  configurable: true,
  writable: true,
});

Object.defineProperty(Event, 'AT_TARGET', {
  value: 2,
  configurable: true,
  writable: true,
});

Object.defineProperty(Event, 'BUBBLING_PHASE', {
  value: 3,
  configurable: true,
  writable: true,
});

// and the same change for the four definitions on Event.prototype
// e.g. Object.defineProperty(Event.prototype, 'NONE', { …configurable: true, writable: true })

This keeps the numeric values and public API unchanged, but avoids the TypeError and restores compatibility with event-target-shim/abort-controller-based code.

[rafaelpierri]

React Native Issue #54732 - Additional Confirmation

Summary

Confirming the bug and providing an additional affected use case with @clerk/clerk-expo authentication library.

Environment

Component	Version
React Native	0.81.4
Expo SDK	54
Platform	Android (emulator, API 35)
Architecture	New Architecture enabled
Host	WSL2 on Windows 11

Affected Library

• Package: @clerk/clerk-expo (v2.16.1)
• Use case: OAuth authentication (Google Sign-In)

Reproduction Steps

1. Create an Expo app with @clerk/clerk-expo for authentication
2. Configure Google OAuth in Clerk Dashboard
3. Attempt to sign in with Google
4. Observe network requests failing

Error Output

TypeError: Cannot assign to read-only property 'NONE'
    at Event (Event.js:52:8)
    at anonymous (WebSocket.js:278:37)
    at apply (native)
    at emit (EventEmitter.js:130:36)

This cascades to a secondary error because the API response is never received:

TypeError: Cannot read property 'toString' of null

The full error from Clerk:

Error: ClerkJS: Network error at "https://[instance].clerk.accounts.dev/v1/client/sign_ins?..."
- TypeError: Cannot assign to read-only property 'NONE'. Please try again.

Root Cause

The error originates from event-target-shim (dependency chain: abort-controller → fetch) attempting to assign to Event.NONE, which is defined without writable: true in React Native's Event implementation.

File: src/private/webapis/dom/events/Event.js

Verified Fix

Applied a patch using patch-package that:

1. Adds writable: true, configurable: true to all 8 Object.defineProperty calls
2. Changes line 72 from Event.NONE to literal 0 (since Event.NONE is referenced before it's defined)

Patch Diff

diff --git a/node_modules/react-native/src/private/webapis/dom/events/Event.js b/node_modules/react-native/src/private/webapis/dom/events/Event.js
index 6f61673..9d3effe 100644
--- a/node_modules/react-native/src/private/webapis/dom/events/Event.js
+++ b/node_modules/react-native/src/private/webapis/dom/events/Event.js
@@ -69,7 +69,7 @@ export default class Event {
   [CURRENT_TARGET_KEY]: EventTarget | null = null;

   // $FlowExpectedError[unsupported-syntax]
-  [EVENT_PHASE_KEY]: boolean = Event.NONE;
+  [EVENT_PHASE_KEY]: boolean = 0;

   // $FlowExpectedError[unsupported-syntax]
   [IN_PASSIVE_LISTENER_FLAG_KEY]: boolean = false;
@@ -184,48 +184,64 @@ export default class Event {

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event, 'NONE', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 0,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event.prototype, 'NONE', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 0,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event, 'CAPTURING_PHASE', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 1,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event.prototype, 'CAPTURING_PHASE', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 1,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event, 'AT_TARGET', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 2,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event.prototype, 'AT_TARGET', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 2,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event, 'BUBBLING_PHASE', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 3,
 });

 // $FlowExpectedError[cannot-write]
 Object.defineProperty(Event.prototype, 'BUBBLING_PHASE', {
+  writable: true,
+  configurable: true,
   enumerable: true,
   value: 3,
 });

Result

After applying this patch, Clerk OAuth and all network requests work correctly.

Workaround for Others

Until this is fixed upstream, use patch-package:

# Install patch-package
npm install --save-dev patch-package

# Apply the changes to node_modules/react-native/src/private/webapis/dom/events/Event.js
# Then create the patch
npx patch-package react-native

# Add postinstall script to package.json

Add to package.json:

{
  "scripts": {
    "postinstall": "patch-package"
  }
}

Related Links

• Issue: Event.NONE/CAPTURING_PHASE/AT_TARGET/BUBBLING_PHASE properties missing configurable: true breaks event-target-shim #54732
• Affected file: src/private/webapis/dom/events/Event.js
• Dependency causing the error: event-target-shim (via abort-controller)