Add TruffleRuby support and add it in CI

.github/workflows/test.yml

@@ -6,7 +6,6 @@ jobs:
   ruby-versions:
     uses: ruby/actions/.github/workflows/ruby_versions.yml@master
     with:
-      engine: cruby-jruby
       min_version: 2.5
   test:
     needs: ruby-versions
@@ -22,6 +21,8 @@ jobs:
           - { os: windows-latest, ruby: jruby }
           - { os: macos-latest, ruby: jruby-head }
           - { os: windows-latest, ruby: jruby-head }
+          - { os: windows-latest, ruby: truffleruby }
+          - { os: windows-latest, ruby: truffleruby-head }
         include:
           - { os: windows-latest, ruby: mingw }
           - { os: windows-latest, ruby: mswin }

Rakefile

@@ -11,7 +11,7 @@ Rake::JavaExtensionTask.new("escape") do |ext|
   task :build => :compile
 end
 
-unless RUBY_ENGINE == 'jruby'
+if RUBY_ENGINE == 'ruby'
   require 'rake/extensiontask'
   extask = Rake::ExtensionTask.new("cgi/escape") do |x|
     x.lib_dir.sub!(%r[(?=/|\z)], "/#{RUBY_VERSION}/#{x.platform}")
@@ -22,7 +22,7 @@ Rake::TestTask.new(:test) do |t|
   t.libs << "test/lib"
   if RUBY_ENGINE == 'jruby'
     t.libs << "ext/java/org/jruby/ext/cgi/escape/lib"
-  else
+  elsif RUBY_ENGINE == 'ruby'
     t.libs << "lib/#{RUBY_VERSION}/#{extask.platform}"
   end
   t.ruby_opts << "-rhelper"

ext/cgi/escape/extconf.rb

@@ -1,3 +1,7 @@
 require 'mkmf'
 
-create_makefile 'cgi/escape'
+if RUBY_ENGINE == 'truffleruby'
+  File.write("Makefile", dummy_makefile($srcdir).join(""))
+else
+  create_makefile 'cgi/escape'
+end

lib/cgi/util.rb

@@ -90,9 +90,12 @@ def escapeHTML(string)
     end
   end
 
-  begin
-    require 'cgi/escape'
-  rescue LoadError
+  # TruffleRuby runs the pure-Ruby variant faster, do not use the C extension there
+  unless RUBY_ENGINE == 'truffleruby'
+    begin
+      require 'cgi/escape'
+    rescue LoadError
+    end
   end
 
   # Unescape a string that has been HTML-escaped

test/cgi/test_cgi_util.rb

@@ -262,7 +262,7 @@ def setup
       remove_method :escapeHTML
       alias _unescapeHTML unescapeHTML
       remove_method :unescapeHTML
-    end
+    end if defined?(CGI::Escape)
   end
 
   def teardown
@@ -271,7 +271,7 @@ def teardown
       remove_method :_escapeHTML
       alias unescapeHTML _unescapeHTML
       remove_method :_unescapeHTML
-    end
+    end if defined?(CGI::Escape)
   end
 
   def test_cgi_escapeHTML_with_invalid_byte_sequence