Fix #105: Ensure the callback fiber is always alive as long as the event loop lives

phpunit.xml.dist

@@ -13,6 +13,7 @@
     <testsuites>
         <testsuite name="Main">
             <directory>test</directory>
+            <directory suffix=".phpt">test</directory>
         </testsuite>
     </testsuites>
 </phpunit>

src/EventLoop/Internal/AbstractDriver.php

@@ -498,9 +498,14 @@ private function invokeCallbacks(): void
     {
         while (!$this->microtaskQueue->isEmpty() || !$this->callbackQueue->isEmpty()) {
             /** @noinspection PhpUnhandledExceptionInspection */
-            $yielded = $this->callbackFiber->isStarted()
-                ? $this->callbackFiber->resume()
-                : $this->callbackFiber->start();
+            if ($this->callbackFiber->isSuspended()) {
+                $yielded = $this->callbackFiber->resume();
+            } else {
+                if ($this->callbackFiber->isTerminated()) {
+                    $this->createCallbackFiber();
+                }
+                $yielded = $this->callbackFiber->start();
+            }
 
             if ($yielded !== $this->internalSuspensionMarker) {
                 $this->createCallbackFiber();

test/event_loop_destruction_order.phpt

@@ -0,0 +1,38 @@
+--TEST--
+Issue #105: Ensure the callback fiber is always alive as long as the event loop lives
+--FILE--
+<?php
+
+use Revolt\EventLoop;
+
+require 'vendor/autoload.php';
+
+final class a {
+    private static self $a;
+    public static function getInstance(): self {
+        return self::$a ??= new self;
+    }
+
+    public function __destruct()
+    {
+        echo "Destroying ", self::class, "\n";
+        $suspension = EventLoop::getSuspension();
+        EventLoop::delay(1.0, $suspension->resume(...));
+        $suspension->suspend();
+        echo "Finished " . self::class, "\n";
+    }
+}
+
+EventLoop::defer(function () {
+    echo "start\n";
+});
+
+a::getInstance();
+
+EventLoop::run();
+
+?>
+--EXPECT--
+start
+Destroying a
+Finished a