PHPLIB-345: Fix PHP shutdown error with dangling writable streams (#779)

* PHPLIB-345: Fix PHP shutdown error with dangling writable streams

* Apply feedback from code review

* Extract HEREDOC code to variable to avoid phpcs issues

Author: alcaeus

src/GridFS/StreamWrapper.php

@@ -57,6 +57,14 @@ class StreamWrapper
     /** @var ReadableStream|WritableStream|null */
     private $stream;
 
+    public function __destruct()
+    {
+        /* This destructor is a workaround for PHP trying to use the stream well
+         * after all objects have been destructed. This can cause autoloading
+         * issues and possibly segmentation faults during PHP shutdown. */
+        $this->stream = null;
+    }
+
     /**
      * Return the stream's file document.
      *
@@ -88,6 +96,10 @@ public static function register($protocol = 'gridfs')
      */
     public function stream_close()
     {
+        if (! $this->stream) {
+            return;
+        }
+
         $this->stream->close();
     }
 

tests/GridFS/BucketFunctionalTest.php

@@ -18,17 +18,22 @@
 use function array_merge;
 use function call_user_func;
 use function current;
+use function exec;
 use function fclose;
 use function fread;
 use function fwrite;
 use function hash_init;
+use function implode;
 use function is_callable;
 use function min;
 use function sprintf;
 use function str_repeat;
 use function stream_get_contents;
 use function strlen;
+use function strncasecmp;
 use function substr;
+use const PHP_EOL;
+use const PHP_OS;
 
 /**
  * Functional tests for the Bucket class.
@@ -708,6 +713,29 @@ public function testExistingIndexIsReused()
         $this->assertIndexNotExists($this->chunksCollection->getCollectionName(), 'files_id_1_n_1');
     }
 
+    public function testDanglingOpenWritableStream()
+    {
+        if (! strncasecmp(PHP_OS, 'WIN', 3)) {
+            $this->markTestSkipped('Test does not apply to Windows');
+        }
+
+        $path = __DIR__ . '/../../vendor/autoload.php';
+        $command = <<<CMD
+php -r "require '$path'; \\\$stream = (new MongoDB\Client)->test->selectGridFSBucket()->openUploadStream('filename', ['disableMD5' => true]);" 2>&1
+CMD;
+
+        @exec(
+            $command,
+            $output,
+            $return
+        );
+
+        $this->assertSame(0, $return);
+        $output = implode(PHP_EOL, $output);
+
+        $this->assertSame('', $output);
+    }
+
     /**
      * Asserts that a collection with the given name does not exist on the
      * server.