Make event firing reentrant

Close #4833

spec/suites/core/EventsSpec.js

@@ -341,6 +341,26 @@ describe('Events', function () {
 
 			expect(spy.called).to.be(false);
 		});
+
+		it('handles reentrant event firing', function () {
+			var obj = new L.Evented(),
+			    spy = sinon.spy();
+
+			obj
+				.addEventListener('test1', function () {
+					obj.fire('test2');
+				})
+				.addEventListener('test2', function () {
+					// NOP, just to make sure event actually fires
+				})
+				.addEventListener('test1', function () {
+					obj.removeEventListener('test1', spy);
+				})
+				.addEventListener('test1', spy);
+
+			obj.fireEvent('test1');
+			expect(spy.called).to.be(false);
+		});
 	});
 
 	describe('#on, #off & #fire', function () {

src/core/Events.js

@@ -163,7 +163,7 @@ L.Evented = L.Class.extend({
 					l.fn = L.Util.falseFn;
 					typeListeners.count--;
 
-					if (this._isFiring) {
+					if (this._firingCount) {
 						/* copy array in case events are being fired */
 						listeners = listeners.slice();
 					}
@@ -188,14 +188,14 @@ L.Evented = L.Class.extend({
 			var typeListeners = this._events[type];
 
 			if (typeListeners) {
-				this._isFiring = true;
+				this._firingCount = (this._firingCount + 1) || 1;
 				var listeners = typeListeners.listeners;
 				for (var i = 0, len = listeners.length; i < len; i++) {
 					var l = listeners[i];
 					l.fn.call(l.ctx || this, event);
 				}
 
-				this._isFiring = false;
+				this._firingCount--;
 			}
 		}