feat(core): experimental unstable versioned write for limited use case

.github/workflows/test-multiple-versions.yml

@@ -38,6 +38,7 @@ jobs:
           - 18.0.0-beta-149b420f6-20211119
           - 0.0.0-experimental-149b420f6-20211119
         mode: [withProvider, withoutProvider]
+        versionObject: [withVersionObject, withoutVersionObject]
         testing: [default, alpha]
         exclude:
           - { react: 16.8.6, testing: alpha }
@@ -65,9 +66,10 @@ jobs:
         run: |
           sed -i~ '1s/^/import React from "react";/' tests/*.tsx tests/*/*.tsx
           sed -i~ 's/automatic/classic/' babel.config.js
-      - name: Test ${{ matrix.react }} ${{ matrix.mode }}
+      - name: Test ${{ matrix.react }} ${{ matrix.mode }} ${{ matrix.versionObject }}
         run: |
           yarn add -D react@${{ matrix.react }} react-dom@${{ matrix.react }}
           yarn test:ci
         env:
           PROVIDER_LESS_MODE: ${{ matrix.mode == 'withoutProvider' }}
+          JOTAI_EXPERIMENTAL_VERSION_OBJECT: ${{ matrix.versionObject == 'withVersionObject' }}

src/core/contexts.ts

@@ -1,18 +1,26 @@
 import { createContext } from 'react'
 import type { Context } from 'react'
 import type { Atom, Scope } from './atom'
-import { createStore } from './store'
+import { VERSION_OBJECT, createStore } from './store'
 import type { Store } from './store'
 
+type GetVersion = () => object | undefined
+
 export type ScopeContainer = {
   s: Store
+  v: GetVersion
 }
 
 export const createScopeContainer = (
   initialValues?: Iterable<readonly [Atom<unknown>, unknown]>
 ): ScopeContainer => {
   const store = createStore(initialValues)
-  return { s: store }
+  const getVersion =
+    typeof process === 'object' &&
+    process.env.JOTAI_EXPERIMENTAL_VERSION_OBJECT === 'true'
+      ? store[VERSION_OBJECT]
+      : () => undefined
+  return { s: store, v: getVersion }
 }
 
 type ScopeContext = Context<ScopeContainer>