return-path should be using angle brackets

Author: frederikbosch

src/Header/ReturnPath.php

@@ -9,14 +9,14 @@
 final class ReturnPath implements HeaderInterface
 {
     /**
-     * @var EmailAddress
+     * @var ?EmailAddress
      */
     private $reversePath;
 
     /**
-     * @param EmailAddress $reversePath
+     * @param ?EmailAddress $reversePath
      */
-    public function __construct(EmailAddress $reversePath)
+    public function __construct(?EmailAddress $reversePath = null)
     {
         $this->reversePath = $reversePath;
     }
@@ -34,6 +34,10 @@ public function getName(): HeaderName
      */
     public function getValue(): HeaderValue
     {
-        return HeaderValue::fromEncodedString((string)$this->reversePath);
+        if ($this->reversePath === null) {
+            return new HeaderValue('<>');
+        }
+
+        return HeaderValue::fromEncodedString('<' . $this->reversePath . '>');
     }
 }

test/Unit/Header/ReturnPathTest.php

@@ -15,7 +15,7 @@ final class ReturnPathTest extends AbstractTestCase
      */
     public function it_produces_correct_values($recipientEmail, $headerName, $headerValue): void
     {
-        $header = new ReturnPath(new EmailAddress($recipientEmail));
+        $header = new ReturnPath($recipientEmail);
         $this->assertEquals($headerName, (string)$header->getName());
         $this->assertEquals($headerValue, (string)$header->getValue());
     }
@@ -26,7 +26,8 @@ public function it_produces_correct_values($recipientEmail, $headerName, $header
     public function provideValues(): array
     {
         return [
-            ['[email protected]', 'Return-Path', '[email protected]'],
+            [new EmailAddress('[email protected]'), 'Return-Path', '<[email protected]>'],
+            [null, 'Return-Path', '<>'],
         ];
     }
 }