Serialization of ATTLIST is incorrect

[OlofKalufs]

When parsing and then serializing an XML document with a DTD internal subset containing an ATTLIST, the "<!ATTLIST" part is missing. See this example:

require 'rexml'

xml_string = %{
<!DOCTYPE elem [
   <!ELEMENT elem EMPTY>
   <!ATTLIST elem attr CDATA #REQUIRED>
]>
<elem attr="value"/>
}

xml_document = REXML::Document.new(xml_string)

puts xml_document.to_s
# Outputs:
# <!DOCTYPE elem [
# <!ELEMENT elem EMPTY>
#  elem attr CDATA #REQUIRED>
# ]><elem attr='value'/>

Tried with REXML 3.4.0 on Ruby 3.3.6

[naitoh]

Thanks for your report, There seems to be a problem with rexml 3.2.7 and later.
I will investigate.

$ gem install rexml -v 3.2.6
$ ruby -r rexml -e 'puts REXML::Document.new("<!DOCTYPE elem [<!ATTLIST elem attr CDATA #REQUIRED>]>")'
<!DOCTYPE elem [
<!ATTLIST elem attr CDATA #REQUIRED>
]>

$ gem install rexml -v 3.2.7
$ ruby -r rexml -e 'puts REXML::Document.new("<!DOCTYPE elem [<!ATTLIST elem attr CDATA #REQUIRED>]>")'
<!DOCTYPE elem [
 elem attr CDATA #REQUIRED>
]>

[OlofKalufs]

Ah, good find! I made a PR for this that you're free to merge if you want