Use #around for creation of context for C examples

This fixes segmentation fault in the tests as extending the examples in a before block with override of `#instance_eval` seems to not work.

Also, the context wrap is now opt-in with a helper method, instead of opt-out and relying on `#described_class` (which has slightly different behavior in RSpec 3).

Tested on Ruby 2.1.5 and RSpec 2.99.2.

spec/c/array_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe V8::C::Array do
+  requires_v8_context
+
   it "can store and retrieve a value" do
     o = V8::C::Object::New()
     a = V8::C::Array::New()

spec/c/constants_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe V8::C do
+  requires_v8_context
+
   it "has constant methods for Undefined, Null, True and False" do
     [:Undefined, :Null, :True, :False].each do |name|
       constant = V8::C.send(name)

spec/c/exception_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe V8::C::Exception do
+  requires_v8_context
+
   it "can be thrown from Ruby" do
     t = V8::C::FunctionTemplate::New(method(:explode))
     @cxt.Global().Set("explode", t.GetFunction())

spec/c/external_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe V8::C::External do
+  requires_v8_context
+
   it "can store and retrieve a value" do
     o = Object.new
     external = V8::C::External::New(o)

spec/c/function_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe V8::C::Function do
+  requires_v8_context
+
   it "can be called" do
     fn = run '(function() {return "foo"})'
     fn.Call(@cxt.Global(), []).Utf8Value().should eql "foo"

spec/c/handles_spec.rb

@@ -1,21 +1,17 @@
 require 'spec_helper'
 
 describe "setting up handles scopes" do
-  include ExplicitScoper
-
-  before do
-    def self.instance_eval(*args, &block)
+  around(:each) do |example|
     V8::C::Locker() do
       cxt = V8::C::Context::New()
       begin
         cxt.Enter()
-          super(*args, &block)
+        example.run
       ensure
         cxt.Exit()
       end
     end
   end
-  end
 
   it "can allocate handle scopes" do
       V8::C::HandleScope() do

spec/c/locker_spec.rb

@@ -1,8 +1,6 @@
 require 'spec_helper'
 
 describe V8::C::Locker do
-  include ExplicitScoper
-
   it "can lock and unlock the VM" do
     V8::C::Locker::IsLocked().should be_false
     V8::C::Locker() do

spec/c/object_spec.rb

@@ -1,6 +1,7 @@
 require 'spec_helper'
 
 describe V8::C::Object do
+  requires_v8_context
 
   it "can store and retrieve a value" do
     o = V8::C::Object::New()

spec/c/script_spec.rb

@@ -2,6 +2,8 @@
 require 'spec_helper'
 
 describe V8::C::Script do
+  requires_v8_context
+
   it "can run a script and return a polymorphic result" do
     source = V8::C::String::New("(new Array())")
     filename = V8::C::String::New("<eval>")

spec/c/string_spec.rb

@@ -1,6 +1,8 @@
 require 'spec_helper'
 
 describe V8::C::String do
+  requires_v8_context
+
   it "can hold Unicode values outside the Basic Multilingual Plane" do
     string = V8::C::String::New("\u{100000}")
     string.Utf8Value().should eql "\u{100000}"

spec/c/template_spec.rb

@@ -1,6 +1,7 @@
 require 'spec_helper'
 
 describe V8::C::Template do
+  requires_v8_context
 
   describe V8::C::FunctionTemplate do
     it "can be created with no arguments" do

spec/c/trycatch_spec.rb

@@ -1,6 +1,7 @@
 require 'spec_helper'
 
 describe V8::C::External do
+  requires_v8_context
 
   it "can catch javascript exceptions" do
     V8::C::V8::SetCaptureStackTraceForUncaughtExceptions(true, 99, V8::C::StackTrace::kDetailed)

spec/spec_helper.rb

@@ -11,35 +11,31 @@ def rputs(msg)
   $stdout.flush
 end
 
-module ExplicitScoper;end
-module Autoscope
-  def instance_eval(*args, &block)
-    return super unless low_level_c_spec? && !explicitly_defines_scope?
+module V8ContextHelpers
+  module GroupMethods
+    def requires_v8_context
+      around(:each) do |example|
+        bootstrap_v8_context(&example)
+      end
+    end
+  end
+
+  def bootstrap_v8_context
     V8::C::Locker() do
       V8::C::HandleScope() do
         @cxt = V8::C::Context::New()
         begin
           @cxt.Enter()
-          super(*args, &block)
+          yield
         ensure
           @cxt.Exit()
         end
       end
     end
   end
-
-  def low_level_c_spec?
-    return false unless described_class
-    described_class.name =~ /^V8::C::/
-  end
-
-  def explicitly_defines_scope?
-    is_a?(ExplicitScoper)
-  end
 end
 
 RSpec.configure do |c|
-  c.before(:each) do
-    extend Autoscope
-  end
+  c.include V8ContextHelpers
+  c.extend V8ContextHelpers::GroupMethods
 end