XML::Builder can write invalid XML characters

[RX14]

On crystal 0.21.0

# example.cr
require "xml"

xml = XML.build(indent: 2) do |xml|
  xml.element("example", number: "1") do
    xml.text "foo\0bar"
  end
  xml.element("example", number: "2") do
    xml.text "foo\u{08}bar"
  end
end

puts xml

$ crystal example.cr
<?xml version="1.0"?>
<example number="1">foo</example>
<example number="2">fobar</example>

I expect to see XML::Builder raise, because NUL and DEL cannot be represented in XML. (ref)

[asterite]

Good finding! We should use xmlEncodeSpecialChars, both for texts and attributes, I guess. Nokogiri seems to use that function too.