fix: Bug with logEvent callbacks not being called when unsent events are dropped

src/amplitude-client.js

@@ -1384,7 +1384,14 @@ var _generateApiPropertiesTrackingConfig = function _generateApiPropertiesTracki
  */
 AmplitudeClient.prototype._limitEventsQueued = function _limitEventsQueued(queue) {
   if (queue.length > this.options.savedMaxCount) {
-    queue.splice(0, queue.length - this.options.savedMaxCount);
+    const deletedEvents = queue.splice(0, queue.length - this.options.savedMaxCount);
+    deletedEvents.forEach((event) => {
+      if (type(event.callback) === 'function') {
+        event.callback(0, 'No request sent', {
+          reason: 'Event dropped because options.savedMaxCount exceeded. User may be offline or have a content blocker',
+        });
+      }
+    });
   }
 };
 
@@ -1394,6 +1401,7 @@ AmplitudeClient.prototype._limitEventsQueued = function _limitEventsQueued(queue
  * @callback Amplitude~eventCallback
  * @param {number} responseCode - Server response code for the event / identify upload request.
  * @param {string} responseBody - Server response body for the event / identify upload request.
+ * @param {object} details - (optional) Additional information associated with sending event.
  */
 
 /**
@@ -1684,7 +1692,7 @@ AmplitudeClient.prototype.sendEvents = function sendEvents() {
       //  here.
       // }
     } catch (e) {
-      // utils.log('failed upload');
+      // utils.log.error('failed upload');
     }
   });
 };

test/amplitude-client.js

@@ -1945,6 +1945,33 @@ describe('AmplitudeClient', function () {
       assert.equal(message, 'success');
     });
 
+    it.only('should run the callback even with a dropped unsent event', function () {
+      amplitude.init(apiKey, null, { savedMaxCount: 1 });
+      var counter = 0;
+      var value = null;
+      var message = null;
+      var reason = null;
+      var callback = function (status, response, details) {
+        counter++;
+        value = status;
+        message = response;
+        reason = details.reason;
+      };
+      amplitude.logEvent('DroppedEvent', {}, callback);
+      amplitude.logEvent('SavedEvent', {}, callback);
+      server.respondWith([0, {}, '']);
+      server.respond();
+
+      // verify callback fired
+      assert.equal(counter, 1);
+      assert.equal(value, 0);
+      assert.equal(message, 'No request sent');
+      assert.equal(
+        reason,
+        'Event dropped because options.savedMaxCount exceeded. User may be offline or have a content blocker',
+      );
+    });
+
     it('should run callback once and only after 413 resolved', function () {
       var counter = 0;
       var value = -1;