Go back to associating Apollo context with React.createContext.

Should fix #8790, by allowing multiple copies of `@apollo/client`
(uncommon) to share the same `React.createContext[contextKey]` object.

src/__tests__/__snapshots__/exports.ts.snap

@@ -330,6 +330,7 @@ Array [
   "argumentsObjectFromField",
   "asyncMap",
   "buildQueryFromSelectionSet",
+  "canUseSymbol",
   "canUseWeakMap",
   "canUseWeakSet",
   "checkDocument",

src/react/context/ApolloContext.ts

@@ -1,30 +1,31 @@
 import * as React from 'react';
 import { ApolloClient } from '../../core';
-import { canUseWeakMap } from '../../utilities';
+import { canUseSymbol } from '../../utilities';
+import type { RenderPromises } from '../ssr';
 
 export interface ApolloContextValue {
   client?: ApolloClient<object>;
-  renderPromises?: Record<any, any>;
+  renderPromises?: RenderPromises;
 }
 
 // To make sure Apollo Client doesn't create more than one React context
 // (which can lead to problems like having an Apollo Client instance added
 // in one context, then attempting to retrieve it from another different
 // context), a single Apollo context is created and tracked in global state.
-// We use React.createContext as the key instead of just React to avoid
-// ambiguities between default and namespace React imports.
+const contextKey = canUseSymbol
+  ? Symbol.for('__APOLLO_CONTEXT__')
+  : '__APOLLO_CONTEXT__';
 
-const cache = new (canUseWeakMap ? WeakMap : Map)<
-  typeof React.createContext,
-  React.Context<ApolloContextValue>
->();
-
-export function getApolloContext() {
-  let context = cache.get(React.createContext)!;
+export function getApolloContext(): React.Context<ApolloContextValue> {
+  let context = (React.createContext as any)[contextKey] as React.Context<ApolloContextValue>;
   if (!context) {
-    context = React.createContext<ApolloContextValue>({});
+    Object.defineProperty(React.createContext, contextKey, {
+      value: context = React.createContext<ApolloContextValue>({}),
+      enumerable: false,
+      writable: false,
+      configurable: true,
+    });
     context.displayName = 'ApolloContext';
-    cache.set(React.createContext, context);
   }
   return context;
 }

src/utilities/common/canUse.ts

@@ -4,3 +4,7 @@ export const canUseWeakMap = typeof WeakMap === 'function' && !(
 );
 
 export const canUseWeakSet = typeof WeakSet === 'function';
+
+export const canUseSymbol =
+  typeof Symbol === 'function' &&
+  typeof Symbol.for === 'function';

src/utilities/observables/subclassing.ts

@@ -1,4 +1,5 @@
 import { Observable } from "./Observable";
+import { canUseSymbol } from "..";
 
 // Generic implementations of Observable.prototype methods like map and
 // filter need to know how to create a new Observable from an Observable
@@ -17,7 +18,7 @@ export function fixObservableSubclass<
     // can't assign to it with a normal assignment expression.
     Object.defineProperty(subclass, key, { value: Observable });
   }
-  if (typeof Symbol === "function" && Symbol.species) {
+  if (canUseSymbol && Symbol.species) {
     set(Symbol.species);
   }
   // The "@@species" string is used as a fake Symbol.species value in some