From ee7d76f7af3997d5da378d7cca44d4bafc1ede65 Mon Sep 17 00:00:00 2001
From: Jordan Harband <ljharb@gmail.com>
Date: Wed, 31 Oct 2018 12:03:50 -0700
Subject: [PATCH] [react-is] add back proper AsyncMode symbol, for back compat
 (#13959)

- Partial revert of #13732
 - Fixes #13958.
---
 packages/react-is/src/ReactIs.js                        | 8 +++++---
 packages/react-is/src/__tests__/ReactIs-test.js         | 2 +-
 packages/shared/ReactSymbols.js                         | 3 +++
 packages/shared/__tests__/ReactSymbols-test.internal.js | 7 ++++++-
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/packages/react-is/src/ReactIs.js b/packages/react-is/src/ReactIs.js
index 97a4212d6c85e..0c1edb811370d 100644
--- a/packages/react-is/src/ReactIs.js
+++ b/packages/react-is/src/ReactIs.js
@@ -10,6 +10,7 @@
 'use strict';
 
 import {
+  REACT_ASYNC_MODE_TYPE,
   REACT_CONCURRENT_MODE_TYPE,
   REACT_CONTEXT_TYPE,
   REACT_ELEMENT_TYPE,
@@ -32,6 +33,7 @@ export function typeOf(object: any) {
         const type = object.type;
 
         switch (type) {
+          case REACT_ASYNC_MODE_TYPE:
           case REACT_CONCURRENT_MODE_TYPE:
           case REACT_FRAGMENT_TYPE:
           case REACT_PROFILER_TYPE:
@@ -57,8 +59,8 @@ export function typeOf(object: any) {
   return undefined;
 }
 
-// AsyncMode alias is deprecated along with isAsyncMode
-export const AsyncMode = REACT_CONCURRENT_MODE_TYPE;
+// AsyncMode is deprecated along with isAsyncMode
+export const AsyncMode = REACT_ASYNC_MODE_TYPE;
 export const ConcurrentMode = REACT_CONCURRENT_MODE_TYPE;
 export const ContextConsumer = REACT_CONTEXT_TYPE;
 export const ContextProvider = REACT_PROVIDER_TYPE;
@@ -86,7 +88,7 @@ export function isAsyncMode(object: any) {
       );
     }
   }
-  return isConcurrentMode(object);
+  return isConcurrentMode(object) || typeOf(object) === REACT_ASYNC_MODE_TYPE;
 }
 export function isConcurrentMode(object: any) {
   return typeOf(object) === REACT_CONCURRENT_MODE_TYPE;
diff --git a/packages/react-is/src/__tests__/ReactIs-test.js b/packages/react-is/src/__tests__/ReactIs-test.js
index 6fc58b34cf07d..3cf74ea6febb9 100644
--- a/packages/react-is/src/__tests__/ReactIs-test.js
+++ b/packages/react-is/src/__tests__/ReactIs-test.js
@@ -69,7 +69,7 @@ describe('ReactIs', () => {
     expect(ReactIs.isValidElementType({type: 'div', props: {}})).toEqual(false);
   });
 
-  it('should identify async mode', () => {
+  it('should identify concurrent mode', () => {
     expect(ReactIs.typeOf(<React.unstable_ConcurrentMode />)).toBe(
       ReactIs.ConcurrentMode,
     );
diff --git a/packages/shared/ReactSymbols.js b/packages/shared/ReactSymbols.js
index cc86ccbeeb723..a2a7c3c009b85 100644
--- a/packages/shared/ReactSymbols.js
+++ b/packages/shared/ReactSymbols.js
@@ -32,6 +32,9 @@ export const REACT_PROVIDER_TYPE = hasSymbol
 export const REACT_CONTEXT_TYPE = hasSymbol
   ? Symbol.for('react.context')
   : 0xeace;
+export const REACT_ASYNC_MODE_TYPE = hasSymbol
+  ? Symbol.for('react.async_mode')
+  : 0xeacf;
 export const REACT_CONCURRENT_MODE_TYPE = hasSymbol
   ? Symbol.for('react.concurrent_mode')
   : 0xeacf;
diff --git a/packages/shared/__tests__/ReactSymbols-test.internal.js b/packages/shared/__tests__/ReactSymbols-test.internal.js
index 4ba3ad9a8b9ad..f62ce65b9eb54 100644
--- a/packages/shared/__tests__/ReactSymbols-test.internal.js
+++ b/packages/shared/__tests__/ReactSymbols-test.internal.js
@@ -31,7 +31,12 @@ describe('ReactSymbols', () => {
     const originalSymbolFor = global.Symbol.for;
     global.Symbol.for = null;
     try {
-      expectToBeUnique(Object.entries(require('shared/ReactSymbols')));
+      const entries = Object.entries(require('shared/ReactSymbols')).filter(
+        // REACT_ASYNC_MODE_TYPE and REACT_CONCURRENT_MODE_TYPE have the same numeric value
+        // for legacy backwards compatibility
+        ([key]) => key !== 'REACT_ASYNC_MODE_TYPE',
+      );
+      expectToBeUnique(entries);
     } finally {
       global.Symbol.for = originalSymbolFor;
     }