Symfony version(s) affected

4.4

Description

in class Symfony\Component\Mime\Test\Constraint\EmailHeaderSame there is this method:

private function getHeaderValue($message): string
    {
        $header = $message->getHeaders()->get($this->headerName);

        return $header instanceof UnstructuredHeader ? $header->getValue() : $header->getBodyAsString();
    }

in the last line, the value of $header is only checked on UnstructuredHeader class. It should be checked at least for not being null (but I guess indeed it should be checked for any class containing the getBodyAsString method)

How to reproduce

Make a test where you check an e-mail header, for example:

public function testEmailIsSentWithHeader(): void
{
    // do something where your email is sent...
    // [...]
    self::assertEmailCount(1);
    $email = self::getMailerMessage();
    self::assertNotNull($email);
    self::assertEmailHeaderSame($email, 'Content-Type', 'X-foo');
}

in the last line you get

Error: Call to a member function getBodyAsString() on null
/prj/vendor/symfony/mime/Test/Constraint/EmailHeaderSame.php:67
/prj/vendor/symfony/mime/Test/Constraint/EmailHeaderSame.php:48
/prj/vendor/symfony/framework-bundle/Test/MailerAssertionsTrait.php:80
/prj/tests/MyTest.php:42

Possible Solution

Check for type of $header variable (see above)

Additional Context

No response