Set a Part filename if the part stores an attachment

This change simplistically sets a Part's filename property if the
content disposition header is set, it's an attachment, and the filename
property is set. I've deliberately avoided any considerations about
sanitising the filename, deciding, at this stage, to leave that to the
calling code up the line.

Signed-off-by: Matthew Setter <matthew@matthewsetter.com>

src/Message.php

@@ -2,18 +2,17 @@
 
 namespace Laminas\Mime;
 
+use Laminas\Mail\Header\ContentDisposition;
 use Laminas\Mail\Header\ContentType;
 use Laminas\Mail\Header\HeaderInterface;
 use Laminas\Mail\Headers;
-use Laminas\Mime\Mime;
-use Laminas\Mime\Part;
-
 use function array_keys;
 use function base64_decode;
 use function count;
 use function current;
 use function quoted_printable_decode;
 use function sprintf;
+use function str_starts_with;
 use function strlen;
 use function strpos;
 use function strtolower;
@@ -333,6 +332,17 @@ public static function createFromMessage($message, $boundary = null, $EOL = Mime
                 }
             } else {
                 $newPart = new Part($body);
+
+                if ($headers->has('content-disposition')) {
+                    /** @var ContentDisposition $header */
+                    $header = $headers->get('content-disposition');
+                    if (
+                        str_starts_with($header->getFieldValue(), 'attachment')
+                        && $header->getParameter('filename') !== null
+                    ) {
+                        $newPart->setFileName($header->getParameter('filename'));
+                    }
+                }
             }
             foreach ($properties as $key => $value) {
                 $newPart->$key = $value;

test/MessageTest.php

@@ -402,6 +402,8 @@ public function testDecodeMultipartMimeMessageWithMessagePartAlternatives()
             );
         }, ARRAY_FILTER_USE_BOTH);
         $this->assertCount(1, $attachments);
+        $docAttachment = $attachments[1];
+        $this->assertSame("DockMcWordface.docx", $docAttachment->getFileName());
 
         $nonAttachments = array_filter($parts, function ($part, $index) {
             return ! str_starts_with(