feat: export piniaSymbol (#2973)

* feat: export piniaSymbol

* chore: doc piniaSymbol

---------

Co-authored-by: xiongjie <jiexiong@futunn.com>
Co-authored-by: Eduardo San Martin Morote <posva13@gmail.com>

Author: 3 people

packages/pinia/src/index.ts

@@ -1,7 +1,7 @@
 /**
  * @module pinia
  */
-export { setActivePinia, getActivePinia } from './rootStore'
+export { setActivePinia, getActivePinia, piniaSymbol } from './rootStore'
 export { createPinia, disposePinia } from './createPinia'
 export type { Pinia, PiniaPlugin, PiniaPluginContext } from './rootStore'
 

packages/pinia/src/rootStore.ts

@@ -111,6 +111,17 @@ export interface Pinia {
   _testing?: boolean
 }
 
+/**
+ * Symbol used to provide/inject the pinia instance in the app. Used internally
+ * and exposed for testing purposes and edge cases like storybook. Could break
+ * in a minor, **USE AT YOUR OWN RISK**.
+ *
+ * For context, see:
+ * - https://github.com/vuejs/pinia/issues/870
+ * - https://github.com/vuejs/pinia/pull/2973
+ *
+ * @internal
+ */
 export const piniaSymbol = (
   __DEV__ ? Symbol('pinia') : /* istanbul ignore next */ Symbol()
 ) as InjectionKey<Pinia>