The document type "..." is not allowed

[crazycodr]

I've just forked the serializer to find out that the tests are not passing. There seems to be a failure and an error which are both related to the inner entity in the doctype.

Tests failing are:

• JMS\Serializer\Tests\Serializer\XmlSerializationTest::testWhitelistedDocumentTypesAreAllowed
• JMS\Serializer\Tests\Serializer\XmlSerializationTest::testExternalEntitiesAreDisabledByDefault

After an hour or so studying the code, i came to conclusion that the code is fine and the tests are the problem. In both tests, we expect the doctype to be:

<!DOCTYPE author [<!ENTITY foo SYSTEM "php://filter/read=convert.base64-encode/resource='.basename(__FILE__).'">]>

While, the doctype resolves to the internalSubset instead of the whole DocType. So the value that becomes expected should be:

<!ENTITY foo SYSTEM "php://filter/read=convert.base64-encode/resource='.basename(__FILE__).'">

Now, i'm not a super fan of XML but i'm pretty sure the code actually works. Can anyone confirm that the tests are really incorrect? If so, i'll PR with the fix asap.

Thanks