From b9ed06b02aa3cee4e78afee86176fdadd607e66b Mon Sep 17 00:00:00 2001
From: Kurt Preston <kpreston@drw.com>
Date: Tue, 15 Dec 2020 18:23:32 -0600
Subject: [PATCH] Log at highest level that has its threshold crossed

---
 src/strongbus.ts      | 10 +++----
 src/strongbus_spec.ts | 65 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/src/strongbus.ts b/src/strongbus.ts
index c0aef45..a81e1af 100644
--- a/src/strongbus.ts
+++ b/src/strongbus.ts
@@ -408,13 +408,13 @@ export class Bus<TEventMap extends object = object> implements Scannable<TEventM
   private addListener(event: EventKeys<TEventMap>|Events.WILDCARD, handler: EventHandlers.GenericHandler): Events.Subscription {
     const {thresholds, logger} = this.options;
     const handlers = this.bus.get(event);
-    const n: number = handlers?.size || 0;
-    if(n > thresholds.info) {
-      logger.info(`${this.name} has ${n} listeners for "${event}", ${thresholds.info} max listeners expected.`);
+    const n: number = handlers?.size + 1 || 1;
+    if(n > thresholds.error) {
+      logger.error(`Potential Memory Leak. ${this.name} has ${n} listeners for "${event}", exceeds threshold set to ${thresholds.error}`);
     } else if(n > thresholds.warn) {
       logger.warn(`Potential Memory Leak. ${this.name} has ${n} listeners for "${event}", exceeds threshold set to ${thresholds.warn}`);
-    } else if(n > thresholds.error) {
-      logger.error(`Potential Memory Leak. ${this.name} has ${n} listeners for "${event}", exceeds threshold set to ${thresholds.error}`);
+    } else if(n > thresholds.info) {
+      logger.info(`${this.name} has ${n} listeners for "${event}", ${thresholds.info} max listeners expected.`);
     }
     this.willAddListener(event);
     const {added} = addListener(this.bus, event, handler);
diff --git a/src/strongbus_spec.ts b/src/strongbus_spec.ts
index 3a2aa60..484ef15 100644
--- a/src/strongbus_spec.ts
+++ b/src/strongbus_spec.ts
@@ -2,6 +2,7 @@ import {sleep} from 'jaasync/lib/cancelable';
 
 import * as Strongbus from './';
 import {Scanner} from './scanner';
+import {Logger} from './types/logger';
 import {EventKeys} from './types/utility';
 
 type TestEventMap = {
@@ -92,6 +93,70 @@ describe('Strongbus.Bus', () => {
     });
   });
 
+  describe('listener logging thresholds', () => {
+    let logger: jasmine.SpyObj<Logger>;
+
+    function addListeners(numListenersToAdd: number) {
+      for(let i = 0; i < numListenersToAdd; i++) {
+        bus.on('bar', () => true);
+      }
+    }
+
+    beforeEach(() => {
+      logger = jasmine.createSpyObj('logger', ['info', 'warn', 'error']);
+    });
+
+    it('logs if the number of listeners exceeds the thresholds', () => {
+      bus = new Strongbus.Bus<TestEventMap>({
+        logger,
+        thresholds: {
+          info: 10,
+          warn: 20,
+          error: 30
+        }
+      });
+      // no logging up to the threshold
+      addListeners(10);
+      expect(logger.info).not.toHaveBeenCalled();
+      expect(logger.warn).not.toHaveBeenCalled();
+      expect(logger.error).not.toHaveBeenCalled();
+
+      // 11th listener triggers info
+      addListeners(1);
+      expect(bus.listeners.get('bar').size).toEqual(11);
+      expect(logger.info).toHaveBeenCalledTimes(1);
+      expect(logger.warn).not.toHaveBeenCalled();
+      expect(logger.error).not.toHaveBeenCalled();
+
+      // 21st listener triggers warn
+      addListeners(10);
+      expect(logger.info).toHaveBeenCalledTimes(10);
+      expect(logger.warn).toHaveBeenCalledTimes(1);
+      expect(logger.error).not.toHaveBeenCalled();
+
+      // 31st listener triggers error
+      addListeners(10);
+      expect(logger.info).toHaveBeenCalledTimes(10);
+      expect(logger.warn).toHaveBeenCalledTimes(10);
+      expect(logger.error).toHaveBeenCalledTimes(1);
+    });
+
+    it('logs at the highest severity that passes the threshold', () => {
+      bus = new Strongbus.Bus<TestEventMap>({
+        logger,
+        thresholds: {
+          // only warn-level specified, info is at default of 100
+          warn: 20
+        }
+      });
+
+      addListeners(21);
+      expect(logger.info).not.toHaveBeenCalled();
+      expect(logger.warn).toHaveBeenCalledTimes(1);
+      expect(logger.error).not.toHaveBeenCalled();
+    });
+  });
+
   describe('#on', () => {
     it('subscribes handler to an event as a key of its typemap', () => {
       const handleFoo = jasmine.createSpy('handleFoo') as (fooPayload: string) => void;