Add runtime using GraalJS on TruffleRuby

* Use Truffle inner contexts to provide correct isolation between ExecJS::Context
* To run the tests:
TRUFFLERUBYOPT="--jvm --polyglot" bundle exec rake test:graaljs TESTOPTS="--seed=0 --verbose"
* Full command without subprocess:
TRUFFLERUBYOPT="--jvm --polyglot" jt -u jvm-js ruby -w -Ilib:test -I $PWD/vendor/bundle/truffleruby/*/gems/rake-13.0.1/lib $PWD/vendor/bundle/truffleruby/*/gems/rake-13.0.1/lib/rake/rake_test_loader.rb test/test_execjs.rb --seed=0 --verbose
* Try command:
TRUFFLERUBYOPT="--jvm --polyglot" jt -u jvm-js ruby -Ilib -rexecjs -e 'p ExecJS.eval("2 + 3")'

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '3.0', '2.7', '2.6', '2.5', 'jruby', 'truffleruby' ]
+        ruby: [ '3.0', '2.7', '2.6', '2.5', 'jruby', 'truffleruby', 'truffleruby+graalvm-head' ]
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -18,12 +18,17 @@ jobs:
         uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
+
       - name: Update Rubygems
         run: gem update --system
       - name: Install bundler
         run: gem install bundler -v '2.2.16'
       - name: Install dependencies
         run: bundle install
+
+      - name: Set TRUFFLERUBYOPT
+        run: echo "TRUFFLERUBYOPT=--jvm --polyglot" >> $GITHUB_ENV
+        if: matrix.ruby == 'truffleruby+graalvm-head'
       - name: Run test
         run: rake
       - name: Install gem

lib/execjs/graaljs_runtime.rb

@@ -0,0 +1,149 @@
+require "execjs/runtime"
+
+module ExecJS
+  class GraalJSRuntime < Runtime
+    class Context < Runtime::Context
+      def initialize(runtime, source = "", options = {})
+        @context = Polyglot::InnerContext.new
+        @context.eval('js', 'delete this.console')
+        @js_object = @context.eval('js', 'Object')
+
+        source = encode(source)
+
+        @source = source
+        unless source.empty?
+          translate do
+            eval_in_context(source)
+          end
+        end
+      end
+
+      def exec(source, options = {})
+        source = encode(source)
+        source = "(function(){#{source}})()" if /\S/.match?(source)
+        source = "#{@source};\n#{source}" unless @source.empty?
+
+        translate do
+          eval_in_context(source)
+        end
+      end
+
+      def eval(source, options = {})
+        source = encode(source)
+        source = "(#{source})" if /\S/.match?(source)
+        source = "#{@source};\n#{source}" unless @source.empty?
+
+        translate do
+          eval_in_context(source)
+        end
+      end
+
+      def call(source, *args)
+        source = encode(source)
+        source = "(#{source})" if /\S/.match?(source)
+        source = "#{@source};\n#{source}" unless @source.empty?
+
+        translate do
+          function = eval_in_context(source)
+          function.call(*convert_ruby_to_js(args))
+        end
+      end
+
+      private
+
+      def translate
+        begin
+          convert_js_to_ruby yield
+        rescue ::RuntimeError => e
+          if e.message.start_with?('SyntaxError:')
+            error_class = ExecJS::RuntimeError
+          else
+            error_class = ExecJS::ProgramError
+          end
+
+          backtrace = e.backtrace.map { |line| line.sub('(eval)', '(execjs)') }
+          raise error_class, e.message, backtrace
+        end
+      end
+
+      def convert_js_to_ruby(value)
+        case value
+        when true, false, Integer, Float
+          value
+        else
+          if value.nil?
+            nil
+          elsif value.respond_to?(:call)
+            nil
+          elsif value.respond_to?(:to_str)
+            value.to_str
+          elsif value.respond_to?(:to_ary)
+            value.to_ary.map do |e|
+              if e.respond_to?(:call)
+                nil
+              else
+                convert_js_to_ruby(e)
+              end
+            end
+          else
+            object = value
+            h = {}
+            object.instance_variables.each do |member|
+              v = object[member]
+              unless v.respond_to?(:call)
+                h[member.to_s] = convert_js_to_ruby(v)
+              end
+            end
+            h
+          end
+        end
+      end
+
+      def convert_ruby_to_js(value)
+        case value
+        when nil, true, false, Integer, Float, String
+          value
+        when Array
+          value.map { |e| convert_ruby_to_js(e) }
+        when Hash
+          h = @js_object.new
+          value.each_pair do |k,v|
+            h[convert_ruby_to_js(k)] = convert_ruby_to_js(v)
+          end
+          h
+        else
+          raise TypeError, "Unknown how to convert to JS: #{value.inspect}"
+        end
+      end
+
+      class_eval <<-'RUBY', "(execjs)", 1
+        def eval_in_context(code); @context.eval('js', code); end
+      RUBY
+    end
+
+    def name
+      "GraalVM (Graal.js)"
+    end
+
+    def available?
+      return @available if defined?(@available)
+
+      unless RUBY_ENGINE == "truffleruby"
+        return @available = false
+      end
+
+      unless defined?(Polyglot::InnerContext)
+        warn "TruffleRuby #{RUBY_ENGINE_VERSION} does not have support for inner contexts, use a more recent version", uplevel: 0
+        return @available = false
+      end
+
+      unless Polyglot.languages.include? "js"
+        warn "The language 'js' is not available, you likely need to `export TRUFFLERUBYOPT='--jvm --polyglot'`", uplevel: 0
+        warn "Note that you need TruffleRuby+GraalVM and not just the TruffleRuby standalone to use #{self.class}", uplevel: 0
+        return @available = false
+      end
+
+      @available = true
+    end
+  end
+end

lib/execjs/runtimes.rb

@@ -4,6 +4,7 @@
 require "execjs/external_runtime"
 require "execjs/ruby_rhino_runtime"
 require "execjs/mini_racer_runtime"
+require "execjs/graaljs_runtime"
 
 module ExecJS
   module Runtimes
@@ -13,6 +14,8 @@ module Runtimes
 
     RubyRhino = RubyRhinoRuntime.new
 
+    GraalJS = GraalJSRuntime.new
+
     MiniRacer = MiniRacerRuntime.new
 
     Node = ExternalRuntime.new(
@@ -82,6 +85,7 @@ def self.names
     def self.runtimes
       @runtimes ||= [
         RubyRhino,
+        GraalJS,
         Duktape,
         MiniRacer,
         Node,