As discussed elsewhere, Nokogumbo and Nokogiri will be merging. The net result of this will be a single gem that provides both Nokogiri::HTML (nokogiri 1.11 and earlier) and Nokogiri::HTML5 (nokogumbo) in the same gem.

My current plan is simply to lift-and-shift the Nokogumbo code into the Nokogiri repository and gem in Nokogiri v1.12. Unless we do something, this will mean that users of Nokogumbo will see warning messages like this when they upgrade Nokogiri:

/home/flavorjones/code/oss/nokogumbo/lib/nokogumbo/html5.rb:7: warning: method redefined; discarding old HTML5
/home/flavorjones/code/oss/nokogiri/lib/nokogiri/html.rb:42: warning: previous definition of HTML5 was here
/home/flavorjones/code/oss/nokogumbo/lib/nokogumbo/html5.rb:13: warning: already initialized constant Nokogiri::HTML5::HTML_NAMESPACE
/home/flavorjones/code/oss/nokogiri/lib/nokogiri/html.rb:48: warning: previous definition of HTML_NAMESPACE was here

These warnings aren't just annoying; they tell us that Nokogumbo's implementation is clobbering the Nokogiri implementation, meaning that until the issue is resolved, updates to Nokogiri's code won't have any effect.