Add new error throwing trait

Author: Charlotte Dunois

src/EventEmitterErrorTrait.php

@@ -0,0 +1,54 @@
+<?php
+/**
+ * EventEmitter
+ * Copyright 2018 Charlotte Dunois, All Rights Reserved
+ *
+ * Website: https://charuru.moe
+ * License: https://github.com/CharlotteDunois/EventEmitter/blob/master/LICENSE
+*/
+
+namespace CharlotteDunois\Events;
+
+/**
+ * Our Event Emitter Error Trait. This one throws an exception if there is not an error event listener when an error event gets emitted.
+ */
+trait EventEmitterErrorTrait {
+    use EventEmitterTrait;
+    
+    /**
+     * Emits an event, catching all exceptions and emitting an error event for these exceptions.
+     * @param string  $event
+     * @param mixed   ...$arguments
+     * @return void
+     * @throws \Throwable                                       Any Throwable, Exception, Error or ErrorException by the listener.
+     * @throws \Exception                                       Any Throwable, Exception, Error or ErrorException by the listener.
+     * @throws \Error                                           Any Throwable, Exception, Error or ErrorException by the listener.
+     * @throws \CharlotteDunois\Events\UnhandledErrorException  Thrown when an error event goes unhandled.
+     */
+    function emit(string $event, ...$arguments) {
+        $errorEmpty = ($event === 'error');
+        
+        if(!empty($this->listeners[$event])) {
+            $errorEmpty = false;
+            
+            foreach($this->listeners[$event] as $listener) {
+                $listener(...$arguments);
+            }
+        }
+        
+        if(!empty($this->onceListeners[$event])) {
+            $errorEmpty = false;
+            
+            $listeners = $this->onceListeners[$event];
+            unset($this->onceListeners[$event]);
+            
+            foreach($listeners as $listener) {
+                $listener(...$arguments);
+            }
+        }
+        
+        if($errorEmpty) {
+            throw new \CharlotteDunois\Events\UnhandledErrorException('Unhandled error event', 0, (($arguments[0] ?? null) instanceof \Throwable ? $arguments[0] : null));
+        }
+    }
+}

src/EventEmitterTrait.php

@@ -144,13 +144,13 @@ function listeners(?string $event = null) {
      * @throws \Error                     Any Throwable, Exception, Error or ErrorException by the listener.
      */
     function emit(string $event, ...$arguments) {
-        if(isset($this->listeners[$event])) {
+        if(!empty($this->listeners[$event])) {
             foreach($this->listeners[$event] as $listener) {
                 $listener(...$arguments);
             }
         }
 
-        if(isset($this->onceListeners[$event])) {
+        if(!empty($this->onceListeners[$event])) {
             $listeners = $this->onceListeners[$event];
             unset($this->onceListeners[$event]);
 

src/UnhandledErrorException.php

@@ -0,0 +1,17 @@
+<?php
+/**
+ * EventEmitter
+ * Copyright 2018 Charlotte Dunois, All Rights Reserved
+ *
+ * Website: https://charuru.moe
+ * License: https://github.com/CharlotteDunois/EventEmitter/blob/master/LICENSE
+*/
+
+namespace CharlotteDunois\Events;
+
+/**
+ * Thrown when an error event gets emitted, but not handled (aka no listeners).
+ */
+class UnhandledErrorException extends \RuntimeException {
+    
+}