Make autobatching notification queueing configurable

docs/api/autoBatchEnhancer.mdx

@@ -65,17 +65,30 @@ const store = configureStore({
 
 ```ts title="autoBatchEnhancer signature" no-transpile
 export type SHOULD_AUTOBATCH = string
-export type autoBatchEnhancer = () => StoreEnhancer
+type AutoBatchOptions =
+  | { type: 'tick' }
+  | { type: 'timer'; timeout: number }
+  | { type: 'raf' }
+  | { type: 'callback'; queueNotification: (notify: () => void) => void }
+
+export type autoBatchEnhancer = (options?: AutoBatchOptions) => StoreEnhancer
 ```
 
 Creates a new instance of the autobatch store enhancer.
 
-Any action that is tagged with `action.meta[SHOULD_AUTOBATCH] = true` will be treated as "low-priority", and the enhancer will delay notifying subscribers until either:
+Any action that is tagged with `action.meta[SHOULD_AUTOBATCH] = true` will be treated as "low-priority", and a notification callback will be queued. The enhancer will delay notifying subscribers until either:
 
-- The end of the current event loop tick happens, and a queued microtask runs the notifications
+- The queued callback runs and triggers the notifications
 - A "normal-priority" action (any action _without_ `action.meta[SHOULD_AUTOBATCH] = true`) is dispatched in the same tick
 
-This method currently does not accept any options. We may consider allowing customization of the delay behavior in the future.
+`autoBatchEnhancer` accepts options to configure how the notification callback is queued:
+
+- `{type: 'tick'}: queues using `queueMicrotask` (default)
+- `{type: 'timer, timeout: number}`: queues using `setTimeout`
+- `{type: 'raf'}`: queues using `requestAnimationFrame`
+- `{type: 'callback', queueNotification: (notify: () => void) => void}: lets you provide your own callback
+
+The default behavior is to queue the notifications at the end of the current event loop using `queueMicrotask`.
 
 The `SHOULD_AUTOBATCH` value is meant to be opaque - it's currently a string for simplicity, but could be a `Symbol` in the future.
 
@@ -117,7 +130,7 @@ This enhancer is a variation of the "debounce" approach, but with a twist.
 
 Instead of _just_ debouncing _all_ subscriber notifications, it watches for any actions with a specific `action.meta[SHOULD_AUTOBATCH]: true` field attached.
 
-When it sees an action with that field, it queues a microtask. The reducer is updated immediately, but the enhancer does _not_ notify subscribers right way. If other actions with the same field are dispatched in succession, the enhancer will continue to _not_ notify subscribers. Then, when the queued microtask runs at the end of the event loop tick, it finally notifies all subscribers, similar to how React batches re-renders.
+When it sees an action with that field, it queues a callback. The reducer is updated immediately, but the enhancer does _not_ notify subscribers right way. If other actions with the same field are dispatched in succession, the enhancer will continue to _not_ notify subscribers. Then, when the queued callback runs, it finally notifies all subscribers, similar to how React batches re-renders.
 
 The additional twist is also inspired by React's separation of updates into "low-priority" and "immediate" behavior (such as a render queued by an AJAX request vs a render queued by a user input that should be handled synchronously).
 

packages/toolkit/src/autoBatchEnhancer.ts

@@ -23,9 +23,21 @@ const queueMicrotaskShim =
           }, 0)
         )
 
+export type AutoBatchOptions =
+  | { type: 'tick' }
+  | { type: 'timer'; timeout: number }
+  | { type: 'raf' }
+  | { type: 'callback'; queueNotification: (notify: () => void) => void }
+
+const createQueueWithTimer = (timeout: number) => {
+  return (notify: () => void) => {
+    setTimeout(notify, timeout)
+  }
+}
+
 /**
  * A Redux store enhancer that watches for "low-priority" actions, and delays
- * notifying subscribers until either the end of the event loop tick or the
+ * notifying subscribers until either the queued callback executes or the
  * next "standard-priority" action is dispatched.
  *
  * This allows dispatching multiple "low-priority" actions in a row with only
@@ -36,9 +48,17 @@ const queueMicrotaskShim =
  * This can be added to `action.meta` manually, or by using the
  * `prepareAutoBatched` helper.
  *
+ * By default, it will queue a notification for the end of the event loop tick.
+ * However, you can pass several other options to configure the behavior:
+ * - `{type: 'tick'}: queues using `queueMicrotask` (default)
+ * - `{type: 'timer, timeout: number}`: queues using `setTimeout`
+ * - `{type: 'raf'}`: queues using `requestAnimationFrame`
+ * - `{type: 'callback', queueNotification: (notify: () => void) => void}: lets you provide your own callback
+ *
+ *
  */
 export const autoBatchEnhancer =
-  (): StoreEnhancer =>
+  (options: AutoBatchOptions = { type: 'tick' }): StoreEnhancer =>
   (next) =>
   (...args) => {
     const store = next(...args)
@@ -49,6 +69,15 @@ export const autoBatchEnhancer =
 
     const listeners = new Set<() => void>()
 
+    const queueCallback =
+      options.type === 'tick'
+        ? queueMicrotaskShim
+        : options.type === 'raf'
+        ? requestAnimationFrame
+        : options.type === 'callback'
+        ? options.queueNotification
+        : createQueueWithTimer(options.timeout)
+
     const notifyListeners = () => {
       // We're running at the end of the event loop tick.
       // Run the real listener callbacks to actually update the UI.
@@ -91,7 +120,7 @@ export const autoBatchEnhancer =
             // Make sure we only enqueue this _once_ per tick.
             if (!notificationQueued) {
               notificationQueued = true
-              queueMicrotaskShim(notifyListeners)
+              queueCallback(notifyListeners)
             }
           }
           // Go ahead and process the action as usual, including reducers.

packages/toolkit/src/index.ts

@@ -189,4 +189,5 @@ export {
   SHOULD_AUTOBATCH,
   prepareAutoBatched,
   autoBatchEnhancer,
+  AutoBatchOptions,
 } from './autoBatchEnhancer'

packages/toolkit/src/tests/autoBatchEnhancer.test.ts

@@ -1,7 +1,12 @@
 import { configureStore } from '../configureStore'
 import { createSlice } from '../createSlice'
-import { autoBatchEnhancer, prepareAutoBatched } from '../autoBatchEnhancer'
+import {
+  autoBatchEnhancer,
+  prepareAutoBatched,
+  AutoBatchOptions,
+} from '../autoBatchEnhancer'
 import { delay } from '../utils'
+import { debounce } from 'lodash'
 
 interface CounterState {
   value: number
@@ -26,11 +31,11 @@ const counterSlice = createSlice({
 })
 const { incrementBatched, decrementUnbatched } = counterSlice.actions
 
-const makeStore = () => {
+const makeStore = (autoBatchOptions?: AutoBatchOptions) => {
   return configureStore({
     reducer: counterSlice.reducer,
     enhancers: (existingEnhancers) => {
-      return existingEnhancers.concat(autoBatchEnhancer())
+      return existingEnhancers.concat(autoBatchEnhancer(autoBatchOptions))
     },
   })
 }
@@ -39,16 +44,29 @@ let store: ReturnType<typeof makeStore>
 
 let subscriptionNotifications = 0
 
-beforeEach(() => {
-  subscriptionNotifications = 0
-  store = makeStore()
+const cases: AutoBatchOptions[] = [
+  { type: 'tick' },
+  { type: 'raf' },
+  { type: 'timer', timeout: 0 },
+  { type: 'timer', timeout: 10 },
+  { type: 'timer', timeout: 20 },
+  {
+    type: 'callback',
+    queueNotification: debounce((notify: () => void) => {
+      notify()
+    }, 5),
+  },
+]
 
-  store.subscribe(() => {
-    subscriptionNotifications++
-  })
-})
+describe.each(cases)('autoBatchEnhancer: %j', (autoBatchOptions) => {
+  beforeEach(() => {
+    subscriptionNotifications = 0
+    store = makeStore(autoBatchOptions)
 
-describe('autoBatchEnhancer', () => {
+    store.subscribe(() => {
+      subscriptionNotifications++
+    })
+  })
   test('Does not alter normal subscription notification behavior', async () => {
     store.dispatch(decrementUnbatched())
     expect(subscriptionNotifications).toBe(1)
@@ -58,7 +76,7 @@ describe('autoBatchEnhancer', () => {
     expect(subscriptionNotifications).toBe(3)
     store.dispatch(decrementUnbatched())
 
-    await delay(5)
+    await delay(25)
 
     expect(subscriptionNotifications).toBe(4)
   })
@@ -72,7 +90,7 @@ describe('autoBatchEnhancer', () => {
     expect(subscriptionNotifications).toBe(0)
     store.dispatch(incrementBatched())
 
-    await delay(5)
+    await delay(25)
 
     expect(subscriptionNotifications).toBe(1)
   })
@@ -86,7 +104,7 @@ describe('autoBatchEnhancer', () => {
     expect(subscriptionNotifications).toBe(1)
     store.dispatch(incrementBatched())
 
-    await delay(5)
+    await delay(25)
 
     expect(subscriptionNotifications).toBe(2)
   })
@@ -104,7 +122,7 @@ describe('autoBatchEnhancer', () => {
     store.dispatch(decrementUnbatched())
     expect(subscriptionNotifications).toBe(3)
 
-    await delay(5)
+    await delay(25)
 
     expect(subscriptionNotifications).toBe(3)
   })