add MiniRacer runtime support

Gemfile

@@ -7,4 +7,5 @@ group :test do
   gem 'therubyracer', platform: :mri
   gem 'therubyrhino', ">=1.73.3", platform: :jruby
   gem 'minitest', require: false
+  gem 'mini_racer', platform: :mri
 end

lib/execjs/mini_racer_runtime.rb

@@ -0,0 +1,102 @@
+require "execjs/runtime"
+
+module ExecJS
+  class MiniRacerRuntime < Runtime
+    class Context < Runtime::Context
+      def initialize(runtime, source = "", options={})
+        source = encode(source)
+        @context = ::MiniRacer::Context.new
+        translate do
+          @context.eval(source)
+        end
+      end
+
+      def exec(source, options = {})
+        source = encode(source)
+
+        if /\S/ =~ source
+          eval "(function(){#{source}})()"
+        end
+      end
+
+      def eval(source, options = {})
+        source = encode(source)
+
+        if /\S/ =~ source
+          translate do
+            @context.eval("(#{source})")
+          end
+        end
+      end
+
+      def call(identifier, *args)
+        # TODO optimise generate
+        eval "#{identifier}.apply(this, #{::JSON.generate(args)})"
+      end
+
+      private
+
+      def strip_functions!(value)
+        if Array === value
+          value.map! do |v|
+            if MiniRacer::JavaScriptFunction === value
+              nil
+            else
+              strip_functions!(v)
+            end
+          end
+        elsif Hash === value
+          value.each do |k,v|
+            if MiniRacer::JavaScriptFunction === v
+              value.delete k
+            else
+              value[k] = strip_functions!(v)
+            end
+          end
+          value
+        elsif MiniRacer::JavaScriptFunction === value
+          nil
+        else
+          value
+        end
+      end
+
+      def translate
+        begin
+          strip_functions! yield
+        rescue MiniRacer::RuntimeError => e
+          ex = ProgramError.new e.message
+          if backtrace = e.backtrace
+            backtrace = backtrace.map { |line|
+              if line =~ /JavaScript at/
+                line.sub("JavaScript at ", "")
+                    .sub("<anonymous>", "(execjs)")
+                    .strip
+              else
+                line
+              end
+            }
+            ex.set_backtrace backtrace
+          end
+          raise ex
+        rescue MiniRacer::ParseError => e
+          ex = RuntimeError.new e.message
+          ex.set_backtrace(["(execjs):1"] + e.backtrace)
+          raise ex
+        end
+      end
+
+    end
+
+    def name
+      "mini_racer (V8)"
+    end
+
+    def available?
+      require "mini_racer"
+      true
+    rescue LoadError
+      false
+    end
+  end
+end

lib/execjs/runtimes.rb

@@ -4,6 +4,7 @@ require "execjs/duktape_runtime"
 require "execjs/external_runtime"
 require "execjs/ruby_racer_runtime"
 require "execjs/ruby_rhino_runtime"
+require "execjs/mini_racer_runtime"
 
 module ExecJS
   module Runtimes
@@ -15,6 +16,8 @@ module ExecJS
 
     RubyRhino = RubyRhinoRuntime.new
 
+    MiniRacer = MiniRacerRuntime.new
+
     Node = ExternalRuntime.new(
       name:        "Node.js (V8)",
       command:     ["nodejs", "node"],
@@ -79,6 +82,7 @@ module ExecJS
         RubyRacer,
         RubyRhino,
         Duktape,
+        MiniRacer,
         Node,
         JavaScriptCore,
         SpiderMonkey,