NoMethodError undefined method get_header re-emerged with JRuby Rack 1.2.2

[chadlwilson]

jruby-rack 1.2.x seems to barf while running on app that was previously working fine with

• Java 21
• JRuby 9.4.7.0
• Rails 6.1 w/ Sprockets 4.2.1 and Rack 2.2.9
• jruby-rack 1.1.22
• Jetty 10.0.21 embedded servlet container, Jetty initializing RackServlet and indirectly JRuby runtimes.

NoMethodError (undefined method `get_header' for #<Rack::Handler::Servlet::DefaultEnv:0xfb5b374>):

This seems to be a re-emergence of #211, previously fixed by #212 in 1.1.21 to create Rails 5.x compatibility, but merged only to the 1.1 branch. Not sure if intentional, but might need some cherry-picks back to master for this and possibly others? https://github.com/jruby/jruby-rack/compare/1.1-stable

Happy to try and help where I can if so. I would like to see how to move forward on master to figure out #244 and others so having some working CI of some sort from master helps.