feat(useEventBus): new Function once (vitest-dev#680)

Co-authored-by: Anthony Fu <anthonyfu117@hotmail.com>

packages/core/useEventBus/index.test.ts

@@ -24,6 +24,17 @@ describe('useEventBus', () => {
     reset()
     expect(events).toEqual(emptyMap)
   })
+  it('once event', () => {
+    const { once, emit, reset } = useEventBus<number>('foo')
+    const { inc, count } = useCounter(0)
+    once(inc)
+    emit()
+    emit()
+    emit()
+    expect(count.value).toBe(1)
+    reset()
+    expect(events).toEqual(emptyMap)
+  })
   it('on callback off event', () => {
     const bus = useEventBus<number>('on-callback-off')
     const { count, inc } = useCounter(0)

packages/core/useEventBus/index.ts

@@ -6,7 +6,7 @@ export type EventBusListener<T = unknown> = (event: T) => void
 export type EventBusEvents<T> = EventBusListener<T>[]
 
 export interface EventBusKey<T> extends Symbol { }
-export type EventBusIdentifer<T = unknown> = EventBusKey<T> | string | number
+export type EventBusIdentifier<T = unknown> = EventBusKey<T> | string | number
 
 export interface UseEventBusReturn<T> {
   /**
@@ -15,6 +15,12 @@ export interface UseEventBusReturn<T> {
    * @returns a stop function to remove the current callback.
    */
   on: (listener: EventBusListener<T>) => Fn
+  /**
+   * Similar to `on`, but only fires once
+   * @param listener watch listener.
+   * @returns a stop function to remove the current callback.
+   */
+  once: (listener: EventBusListener<T>) => Fn
   /**
    * Emit an event, the corresponding event listeners will execute.
    * @param event data sent.
@@ -31,7 +37,7 @@ export interface UseEventBusReturn<T> {
   reset: () => void
 }
 
-export function useEventBus<T = unknown>(key: EventBusIdentifer<T>): UseEventBusReturn<T> {
+export function useEventBus<T = unknown>(key: EventBusIdentifier<T>): UseEventBusReturn<T> {
   const scope = getCurrentScope()
 
   function on(listener: EventBusListener<T>) {
@@ -45,6 +51,15 @@ export function useEventBus<T = unknown>(key: EventBusIdentifer<T>): UseEventBus
     return _off
   }
 
+  function once(listener: EventBusListener<T>) {
+    function _listener(...args: any[]) {
+      off(_listener)
+      // @ts-expect-error
+      listener(...args)
+    }
+    return on(_listener)
+  }
+
   function off(listener: EventBusListener<T>): void {
     const listeners = events.get(key)
     if (!listeners)
@@ -65,5 +80,5 @@ export function useEventBus<T = unknown>(key: EventBusIdentifer<T>): UseEventBus
     events.get(key)?.forEach(v => v(event))
   }
 
-  return { on, off, emit, reset }
+  return { on, once, off, emit, reset }
 }

packages/core/useEventBus/internal.ts

@@ -1,4 +1,4 @@
-import { EventBusEvents, EventBusIdentifer } from '.'
+import { EventBusEvents, EventBusIdentifier } from '.'
 
 /* #__PURE__ */
-export const events = new Map<EventBusIdentifer<any>, EventBusEvents<any>>()
+export const events = new Map<EventBusIdentifier<any>, EventBusEvents<any>>()