From aa7594cfac6afd2d3dd9303b3e5fb8f7dcb2cd82 Mon Sep 17 00:00:00 2001
From: Owen Delahoy <github@owendelahoy.com>
Date: Mon, 6 Feb 2023 23:59:09 +0900
Subject: [PATCH 1/3] feat: use storage events to synchronize across windows

---
 src/index.ts | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/index.ts b/src/index.ts
index 45d1871..f4e30fb 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -9,6 +9,7 @@ export interface PersistStorage {
 export interface PersistConfiguration {
   key?: string
   storage?: PersistStorage
+  synchronizeWindows?: boolean
 }
 
 /**
@@ -27,9 +28,13 @@ export const recoilPersist = (
     }
   }
 
-  const { key = 'recoil-persist', storage = localStorage } = config
+  const {
+    key = 'recoil-persist',
+    storage = localStorage,
+    synchronizeWindows = true,
+  } = config
 
-  const persistAtom: AtomEffect<any> = ({ onSet, node, trigger, setSelf }) => {
+  const persistAtom: AtomEffect<any> = ({ onSet, node, trigger, setSelf, resetSelf }) => {
     if (trigger === 'get') {
       const state = getState()
       if (typeof state.then === 'function') {
@@ -52,6 +57,21 @@ export const recoilPersist = (
         updateState(newValue, state, node.key, isReset)
       }
     })
+
+    if(synchronizeWindows) {
+      const onStorageEvent = (e: StorageEvent) => {
+        if(e.key == key) {
+          const state = parseState(e.newValue)
+          if(node.key in state) {
+            setSelf(state[node.key])
+          } else {
+            resetSelf()
+          }
+        }
+      }
+      window.addEventListener('storage', onStorageEvent)
+      return () => window.removeEventListener('storage', onStorageEvent)
+    }
   }
 
   const updateState = (
@@ -84,8 +104,8 @@ export const recoilPersist = (
     return {}
   }
 
-  const parseState = (state: string) => {
-    if (state === undefined) {
+  const parseState = (state?: string | null) => {
+    if (!state) {
       return {}
     }
     try {

From dcc1bceeb29a8cd64ed1a1720e90da6ddb545ff6 Mon Sep 17 00:00:00 2001
From: Owen Delahoy <github@owendelahoy.com>
Date: Tue, 7 Feb 2023 00:18:19 +0900
Subject: [PATCH 2/3] feat: allow configuration of how to add and remove
 StorageEvent listeners

---
 src/index.ts | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/index.ts b/src/index.ts
index f4e30fb..d5bc962 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -6,10 +6,15 @@ export interface PersistStorage {
   getItem(key: string): null | string | Promise<string>
 }
 
+export interface StorageEvent {
+  readonly key?: string | null;
+  readonly newValue?: string | null;
+}
+
 export interface PersistConfiguration {
   key?: string
   storage?: PersistStorage
-  synchronizeWindows?: boolean
+  addStorageListener?: (listener: (e: StorageEvent) => void) => ReturnType<AtomEffect<any>>
 }
 
 /**
@@ -18,6 +23,9 @@ export interface PersistConfiguration {
  * @param config Optional configuration object
  * @param config.key Used as key in local storage, defaults to `recoil-persist`
  * @param config.storage Local storage to use, defaults to `localStorage`
+ * @param config.addStorageListener Optional method to listen to storage events
+ * enabling external events to trigger application updates
+ * defaults to `localStorage` events synchronizing multiple windows
  */
 export const recoilPersist = (
   config: PersistConfiguration = {},
@@ -31,7 +39,10 @@ export const recoilPersist = (
   const {
     key = 'recoil-persist',
     storage = localStorage,
-    synchronizeWindows = true,
+    addStorageListener = (listener) => {
+      window.addEventListener('storage', listener)
+      return () => window.removeEventListener('storage', listener)
+    },
   } = config
 
   const persistAtom: AtomEffect<any> = ({ onSet, node, trigger, setSelf, resetSelf }) => {
@@ -58,8 +69,8 @@ export const recoilPersist = (
       }
     })
 
-    if(synchronizeWindows) {
-      const onStorageEvent = (e: StorageEvent) => {
+    if(addStorageListener) {
+      const removeStorageListener = addStorageListener((e: StorageEvent) => {
         if(e.key == key) {
           const state = parseState(e.newValue)
           if(node.key in state) {
@@ -68,9 +79,8 @@ export const recoilPersist = (
             resetSelf()
           }
         }
-      }
-      window.addEventListener('storage', onStorageEvent)
-      return () => window.removeEventListener('storage', onStorageEvent)
+      });
+      return removeStorageListener;
     }
   }
 

From f9232d2f8292e8a7cdd288bbd48af621afd6d70b Mon Sep 17 00:00:00 2001
From: Owen Delahoy <github@owendelahoy.com>
Date: Tue, 7 Feb 2023 00:41:09 +0900
Subject: [PATCH 3/3] fix: allow addStorageListener to be null to disable
 synchronization

---
 src/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/index.ts b/src/index.ts
index d5bc962..0207264 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -14,7 +14,7 @@ export interface StorageEvent {
 export interface PersistConfiguration {
   key?: string
   storage?: PersistStorage
-  addStorageListener?: (listener: (e: StorageEvent) => void) => ReturnType<AtomEffect<any>>
+  addStorageListener?: ((listener: (e: StorageEvent) => void) => ReturnType<AtomEffect<any>>) | null
 }
 
 /**