Handle out-of-order destruction of Fibers/DebugScopes during final shutdown

src/Context/DebugScope.php

@@ -4,10 +4,16 @@
 
 namespace OpenTelemetry\Context;
 
+use function assert;
 use function basename;
+use function class_exists;
 use function count;
 use function debug_backtrace;
 use const DEBUG_BACKTRACE_IGNORE_ARGS;
+use Fiber;
+use const PHP_VERSION_ID;
+use function register_shutdown_function;
+use function spl_object_id;
 use function sprintf;
 use function trigger_error;
 
@@ -16,28 +22,37 @@
  */
 final class DebugScope implements ScopeInterface
 {
-    private const DEBUG_TRACE_CREATE = '__debug_trace_create';
-    private const DEBUG_TRACE_DETACH = '__debug_trace_detach';
+    private static bool $shutdownHandlerInitialized = false;
+    private static bool $finalShutdownPhase = false;
 
     private ContextStorageScopeInterface $scope;
+    private ?int $fiberId;
+    private array $createdAt;
+    private ?array $detachedAt = null;
 
-    public function __construct(ContextStorageScopeInterface $node)
+    public function __construct(ContextStorageScopeInterface $scope)
     {
-        $this->scope = $node;
-        $this->scope[self::DEBUG_TRACE_CREATE] = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+        $this->scope = $scope;
+        $this->fiberId = self::currentFiberId();
+        $this->createdAt = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+
+        if (!self::$shutdownHandlerInitialized) {
+            self::$shutdownHandlerInitialized = true;
+            register_shutdown_function('register_shutdown_function', static fn () => self::$finalShutdownPhase = true);
+        }
     }
 
     public function detach(): int
     {
-        $this->scope[self::DEBUG_TRACE_DETACH] ??= debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+        $this->detachedAt ??= debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
 
         $flags = $this->scope->detach();
 
         if (($flags & ScopeInterface::DETACHED) !== 0) {
             trigger_error(sprintf(
                 'Scope: unexpected call to Scope::detach() for scope #%d, scope was already detached %s',
                 spl_object_id($this),
-                self::formatBacktrace($this->scope[self::DEBUG_TRACE_DETACH]),
+                self::formatBacktrace($this->detachedAt),
             ));
         } elseif (($flags & ScopeInterface::MISMATCH) !== 0) {
             trigger_error(sprintf(
@@ -56,15 +71,39 @@ public function detach(): int
 
     public function __destruct()
     {
-        if (!isset($this->scope[self::DEBUG_TRACE_DETACH])) {
+        if (!$this->detachedAt) {
+            // Handle destructors invoked during final shutdown
+            // DebugScope::__destruct() might be called before fiber finally blocks run
+            if (self::$finalShutdownPhase && $this->fiberId !== self::currentFiberId()) {
+                return;
+            }
+
             trigger_error(sprintf(
                 'Scope: missing call to Scope::detach() for scope #%d, created %s',
                 spl_object_id($this->scope),
-                self::formatBacktrace($this->scope[self::DEBUG_TRACE_CREATE]),
+                self::formatBacktrace($this->createdAt),
             ));
         }
     }
 
+    /**
+     * @phan-suppress PhanUndeclaredClassReference
+     * @phan-suppress PhanUndeclaredClassMethod
+     */
+    private static function currentFiberId(): ?int
+    {
+        if (PHP_VERSION_ID < 80100) {
+            return null;
+        }
+
+        assert(class_exists(Fiber::class, false));
+        if (!$fiber = Fiber::getCurrent()) {
+            return null;
+        }
+
+        return spl_object_id($fiber);
+    }
+
     private static function formatBacktrace(array $trace): string
     {
         $s = '';