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Track event listener count #28

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merged 4 commits into from
Sep 7, 2022
Merged

Track event listener count #28

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c043560
track listener counts internally
Sep 7, 2022
7f1f470
replace call to this.listeners with count read
Sep 7, 2022
ec8206b
add spec for listenerCount
Sep 7, 2022
39a33b4
remove redundant memo
Sep 7, 2022
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78 changes: 45 additions & 33 deletions src/strongbus.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,8 @@ export class Bus<TEventMap extends Events.EventMap = Events.EventMap> implements

private _active = false;
private _delegates = new Map<Bus<TEventMap>, Events.Subscription[]>();
private _delegateListenerTotalCount: number = 0;
private _delegateListenerCountsByEvent = new Map<EventKeys<TEventMap>|Events.WILDCARD, number>();
private readonly subscriptionCache = new Map<string, Events.Subscription>();
private readonly options: Required<Options> & {thresholds: Required<ListenerThresholds>};

Expand Down Expand Up @@ -447,9 +449,9 @@ export class Bus<TEventMap extends Events.EventMap = Events.EventMap> implements
if(!this._delegates.has(delegate)) {
this._delegates.set(delegate, [
delegate.hook(Lifecycle.willAddListener, this.willAddListener),
delegate.hook(Lifecycle.didAddListener, this.didAddDelegateListener),
delegate.hook(Lifecycle.didAddListener, event => this.didAddListener(event, delegate)),
delegate.hook(Lifecycle.willRemoveListener, this.willRemoveListener),
delegate.hook(Lifecycle.didRemoveListener, this.didRemoveDelegateListener)
delegate.hook(Lifecycle.didRemoveListener, event => this.didRemoveListener(event, delegate))
]);
}
}
Expand Down Expand Up @@ -514,12 +516,7 @@ export class Bus<TEventMap extends Events.EventMap = Events.EventMap> implements
* @getter `boolean`
*/
public get hasDelegateListeners(): boolean {
for(const delegate of this._delegates.keys()) {
if(delegate.hasListeners) {
return true;
}
}
return false;
return this._delegateListenerTotalCount > 0;
}

private _cachedGetListersValue: Map<EventKeys<TEventMap>|Events.WILDCARD, ReadonlySet<EventHandlers.GenericHandler>>;
Expand Down Expand Up @@ -559,21 +556,31 @@ export class Bus<TEventMap extends Events.EventMap = Events.EventMap> implements
}

public hasListenersFor(event: EventKeys<TEventMap>|Events.WILDCARD): boolean {
return this.hasOwnListenersFor(event) || this.hasDelegateListenersFor(event);
return this.getListenerCountFor(event) > 0;
}

public hasOwnListenersFor(event: EventKeys<TEventMap>|Events.WILDCARD): boolean {
const handlers = this.bus.get(event);
return handlers?.size > 0;
return this.getOwnListenerCountFor(event) > 0;
}

public hasDelegateListenersFor(event: EventKeys<TEventMap>|Events.WILDCARD): boolean {
for(const delegate of this._delegates.keys()) {
if(delegate.hasListenersFor(event)) {
return true;
}
}
return false;
return this.getDelegateListenerCountFor(event) > 0;
}

public get listenerCount(): number {
return this.bus.size + this._delegateListenerTotalCount;
}

public getListenerCountFor(event: EventKeys<TEventMap>|Events.WILDCARD): number {
return this.getOwnListenerCountFor(event) + this.getDelegateListenerCountFor(event);
}

public getOwnListenerCountFor(event: EventKeys<TEventMap>|Events.WILDCARD): number {
return this.bus.get(event)?.size ?? 0;
}

public getDelegateListenerCountFor(event: EventKeys<TEventMap>|Events.WILDCARD): number {
return (this._delegateListenerCountsByEvent.get(event) ?? 0);
}

/**
Expand Down Expand Up @@ -710,52 +717,57 @@ export class Bus<TEventMap extends Events.EventMap = Events.EventMap> implements

private willAddListener(event: EventKeys<TEventMap>|Events.WILDCARD) {
this.emitLifecycleEvent(Lifecycle.willAddListener, event);
if(!this.active) {
if(!this._active) {
this.emitLifecycleEvent(Lifecycle.willActivate, null);
}
}

private didAddListener(event: EventKeys<TEventMap>|Events.WILDCARD, invokedByDelegate: boolean = false) {
private didAddListener(event: EventKeys<TEventMap>|Events.WILDCARD, bus: Bus<any> = this) {

this._cachedGetListersValue = null;
if(!invokedByDelegate) {
if(bus === this) {
this._cachedGetOwnListenersValue = null;
} else {
const currCount = this._delegateListenerCountsByEvent.get(event) ?? 0;
this._delegateListenerCountsByEvent.set(event, Math.max(currCount + 1, 0));
this._delegateListenerTotalCount = Math.max(this._delegateListenerTotalCount + 1, 0);
}

this.emitLifecycleEvent(Lifecycle.didAddListener, event);
if(!this.active && this.hasListeners) {
if(!this._active && this.hasListeners) {
this._active = true;
this.emitLifecycleEvent(Lifecycle.active, null);
}
}

private didAddDelegateListener(event: EventKeys<TEventMap>|Events.WILDCARD): void {
this.didAddListener(event, true);
}

private willRemoveListener(event: EventKeys<TEventMap>|Events.WILDCARD): void {
const eventHandlerCount = this.listeners.get(event)?.size || 0;
const eventHandlerCount = this.getListenerCountFor(event);
if(eventHandlerCount) {
this.emitLifecycleEvent(Lifecycle.willRemoveListener, event);
if(this.active && this.listeners.size === 1 && eventHandlerCount === 1) {
if(this._active && this.listenerCount === 1 && eventHandlerCount === 1) {
this.emitLifecycleEvent(Lifecycle.willIdle, null);
}
}
}

private didRemoveListener(event: EventKeys<TEventMap>|Events.WILDCARD, invokedByDelegate: boolean = false) {
private didRemoveListener(event: EventKeys<TEventMap>|Events.WILDCARD, bus: Bus<any> = this) {

this._cachedGetListersValue = null;
if(!invokedByDelegate) {
if(bus === this) {
this._cachedGetOwnListenersValue = null;
} else {
const currCount = this._delegateListenerCountsByEvent.get(event) ?? 0;
this._delegateListenerCountsByEvent.set(event, Math.max(currCount - 1, 0));
this._delegateListenerTotalCount = Math.max(this._delegateListenerTotalCount - 1, 0);
}

this.emitLifecycleEvent(Lifecycle.didRemoveListener, event);
if(this.active && !this.hasListeners) {
if(this._active && !this.hasListeners) {
this._active = false;
this.emitLifecycleEvent(Lifecycle.idle, null);
}
}

private didRemoveDelegateListener(event: EventKeys<TEventMap>|Events.WILDCARD): void {
this.didRemoveListener(event, true);
}
}


Expand Down
88 changes: 88 additions & 0 deletions src/strongbus_spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1250,6 +1250,94 @@ describe('Strongbus.Bus', () => {
});
});

describe('#listenerCount', () => {
describe('given an instance has no delegates', () => {
it('counts listeners for the instance', () => {
bus.on('foo', onTestEvent);
bus.on('bar', () => ({}));

expect(bus.listenerCount).toEqual(2);
});
});

describe('given an instance has delegates', () => {
let bus2: DelegateTestBus;
beforeEach(() => {
bus2 = new DelegateTestBus({emulateListenerCount: true});
bus.pipe(bus2);
});

describe('and a delegate has listeners', () => {
it('counts listeners for the instance and its delegates', () => {
bus.on('foo', onTestEvent);
bus.on('bar', () => ({}));
bus2.on('foo', onTestEvent);

expect(bus.listenerCount).toEqual(3);
});
});

describe('and delegates have no listeners', () => {
it('counts listeners for the instance and its delegates', () => {
bus.on('foo', onTestEvent);
bus.on('bar', () => ({}));

expect(bus.listenerCount).toEqual(2);
});
});
});
});

describe('#listenerCount', () => {
describe('given an instance has no delegates', () => {
it('counts listeners for the instance', () => {
const sub1 = bus.on('foo', onTestEvent);
const sub2 = bus.on('bar', () => ({}));

expect(bus.listenerCount).toEqual(2);
sub1.unsubscribe();
expect(bus.listenerCount).toEqual(1);
sub2.unsubscribe();
expect(bus.listenerCount).toEqual(0);
});
});

describe('given an instance has delegates', () => {
let bus2: DelegateTestBus;
beforeEach(() => {
bus2 = new DelegateTestBus({emulateListenerCount: true});
bus.pipe(bus2);
});

describe('and a delegate has listeners', () => {
it('counts listeners for the instance and its delegates', () => {
const sub1 = bus.on('foo', onTestEvent);
const sub2 = bus.on('bar', () => ({}));
const sub3 = bus2.on('foo', onTestEvent);

expect(bus.listenerCount).toEqual(3);
sub1.unsubscribe();
expect(bus.listenerCount).toEqual(2);
sub2.unsubscribe();
expect(bus.listenerCount).toEqual(1);
sub3.unsubscribe();
expect(bus.listenerCount).toEqual(0);
sub1.unsubscribe();
expect(bus.listenerCount).toEqual(0);
});
});

describe('and delegates have no listeners', () => {
it('counts listeners for the instance and its delegates', () => {
bus.on('foo', onTestEvent);
bus.on('bar', () => ({}));

expect(bus.listenerCount).toEqual(2);
});
});
});
});

describe('#destroy', () => {
it('removes all event listeners, triggering proper lifecycle events', () => {
bus = new Strongbus.Bus({allowUnhandledEvents: false});
Expand Down