[chore] Use non-deprecated constant to determine Rack presence and define rack.version

This is more forward compatible with Rack 3.x.

Author: chadlwilson

src/main/ruby/jruby/rack/rack_ext.rb

@@ -9,7 +9,7 @@
   require 'rack'
 rescue LoadError
   require 'vendor/rack'
-end unless defined?(::Rack::VERSION)
+end unless defined?(::Rack::RELEASE)
 
 # Servlet API friendly extensions to Rack
 # Allows for forwarding the request to another servlet/JSP

src/main/ruby/rack/handler/servlet/default_env.rb

@@ -231,7 +231,7 @@ def load_variable(env, key)
 
         def load_builtin(env, key)
           case key
-          when 'rack.version'         then env[key] = ::Rack::VERSION
+          when 'rack.version'         then env[key] = ::Rack::RELEASE
           when 'rack.multithread'     then env[key] = true
           when 'rack.multiprocess'    then env[key] = false
           when 'rack.run_once'        then env[key] = false

src/spec/ruby/jruby/rack/booter_spec.rb

@@ -264,7 +264,7 @@
         # Booter.boot! run :
         should_not_eval_as_nil "ENV['RACK_ENV']"
         # rack got required :
-        should_not_eval_as_nil "defined?(Rack::VERSION)"
+        should_not_eval_as_nil "defined?(Rack::RELEASE)"
         should_not_eval_as_nil "defined?(Rack.release)"
         # check if it got loaded correctly :
         should_not_eval_as_nil "Rack::Request.new({}) rescue nil"
@@ -313,7 +313,7 @@
         should_not_eval_as_nil "ENV['RAILS_ENV']"
 
         # rack not yet required (let bundler decide which rack version to load) :
-        should_eval_as_nil "defined?(Rack::VERSION)"
+        should_eval_as_nil "defined?(Rack::RELEASE)"
         should_eval_as_nil "defined?(Rack.release)"
       end
 

src/spec/ruby/rack/application_spec.rb

@@ -310,7 +310,7 @@ def newRuntime()
 
       it "does not require 'rack' (until booter is called)" do
         @runtime = app_factory.newRuntime
-        should_eval_as_nil "defined?(::Rack::VERSION)"
+        should_eval_as_nil "defined?(::Rack::RELEASE)"
       end
 
       it "loads specified version of rack via bundler", :lib => :stub do

src/spec/ruby/rack/handler/servlet_spec.rb

@@ -44,7 +44,7 @@ def _env
 
     it "creates a hash with the Rack variables in it" do
       hash = servlet.create_env(@servlet_env)
-      expect(hash['rack.version']).to eq Rack::VERSION
+      expect(hash['rack.version']).to eq Rack::RELEASE
       expect(hash['rack.multithread']).to eq true
       expect(hash['rack.multiprocess']).to eq false
       expect(hash['rack.run_once']).to eq false
@@ -204,7 +204,7 @@ def _env
       end
 
       env = servlet.create_env @servlet_env
-      expect(env["rack.version"]).to eq Rack::VERSION
+      expect(env["rack.version"]).to eq Rack::RELEASE
       expect(env["CONTENT_TYPE"]).to eq "text/html"
       expect(env["HTTP_HOST"]).to eq "serverhost"
       expect(env["HTTP_ACCEPT"]).to eq "text/*"