Allowing to quickly duplicates contexts

With a new `deep_clone` method.

Comes in handy for caching base contexts then used to evalaute further scripts.

With proper unit tests on it.

Author: wk8

ext/v8/context.cc

@@ -10,6 +10,7 @@ void Context::Init() {
     defineSingletonMethod("GetCalling", &GetCalling).
     defineSingletonMethod("InContext", &InContext).
     defineMethod("Dispose", &Dispose).
+    defineMethod("Clone", &Clone).
     defineMethod("Global", &Global).
     defineMethod("DetachGlobal", &Global).
     defineMethod("ReattachGlobal", &ReattachGlobal).
@@ -33,6 +34,53 @@ VALUE Context::Dispose(VALUE self) {
   Void(Context(self).dispose())
 }
 
+VALUE Context::Clone(VALUE self, VALUE new_rr_context) {
+  // acquire the lock
+  v8::Locker locker;
+  v8::HandleScope handle_scope;
+
+  // unwrap V8 contexts
+  v8::Context* original_context = *((v8::Handle<v8::Context>) Context(self));
+  v8::Context* new_context = *((v8::Handle<v8::Context>) Context(new_rr_context));
+
+  // get the original global context
+  v8::Local<v8::Value> key, value;
+
+  original_context->Enter();
+
+  v8::Local<v8::Object> original_global(original_context->Global());
+  v8::Local<v8::Array> property_names = original_global->GetPropertyNames();
+  uint32_t i, length = property_names->Length();
+  std::vector< v8::Local<v8::Value> > values;
+
+  for (i = 0; i < length; i++) {
+    key = property_names->Get(i);
+    value = original_global->Get(key);
+    values.push_back(value);
+  }
+
+  original_context->Exit();
+
+  // and copy everything to the new context
+  new_context->Enter();
+
+  v8::Local<v8::Object> new_global(new_context->Global());
+  std::vector< v8::Local<v8::Value> >::iterator it;
+
+  for (i = 0, it = values.begin(); i < length; i++, it++) {
+    key = property_names->Get(i);
+    value = *it;
+    new_global->Set(key, value);
+  }
+
+  new_context->Exit();
+
+  // unlock
+  v8::Unlocker unlocker;
+
+  return Qnil;
+}
+
 VALUE Context::Global(VALUE self) {
   return Object(Context(self)->Global());
 }

ext/v8/rr.h

@@ -306,6 +306,7 @@ class Context : public Ref<v8::Context> {
   static void Init();
   static VALUE New(int argc, VALUE argv[], VALUE self);
   static VALUE Dispose(VALUE self);
+  static VALUE Clone(VALUE self, VALUE new_context);
   static VALUE Enter(VALUE self);
   static VALUE Exit(VALUE self);
   static VALUE Global(VALUE self);

lib/v8/context.rb

@@ -62,9 +62,12 @@ class Context
     #  * :with scope serves as the global scope of the new context
     # @yield [V8::Context] the newly created context
     def initialize(options = {})
+      @options = options
+
       @conversion = Conversion.new
       @access = Access.new
       @timeout = options[:timeout]
+
       if global = options[:with]
         Context.new.enter do
           global_template = global.class.to_template.InstanceTemplate()
@@ -137,6 +140,14 @@ def self.enter
       end
     end
 
+    def deep_clone
+      fail ArgumentError, 'cannot clone an empty context' unless @native
+
+      self.class.new(@options).tap do |new_context|
+        native.Clone(new_context.native)
+      end
+    end
+
     # Returns this context's global object. This will be a `V8::Object`
     # if no scope was provided or just an `Object` if a Ruby object
     # is serving as the global scope.

spec/v8/context_spec.rb

@@ -1,19 +1,92 @@
 require 'spec_helper'
 
 describe V8::Context do
-  it "can be disposed of" do
-    cxt = V8::Context.new
-    cxt.enter do
-      cxt['object'] = V8::Object.new
+  describe '.dispose' do
+    it "can be disposed of" do
+      cxt = V8::Context.new
+      cxt.enter do
+        cxt['object'] = V8::Object.new
+      end
+      cxt.dispose()
+
+      lambda {cxt.eval('1 + 1')}.should raise_error
+      lambda {cxt['object']}.should raise_error
     end
-    cxt.dispose()
 
-    lambda {cxt.eval('1 + 1')}.should raise_error
-    lambda {cxt['object']}.should raise_error
+    it "can be disposed of any number of times" do
+      cxt = V8::Context.new
+      10.times {cxt.dispose()}
+    end
   end
 
-  it "can be disposed of any number of times" do
-    cxt = V8::Context.new
-    10.times {cxt.dispose()}
+  describe '.deep_clone' do
+    let(:js) do
+      <<-js
+        if (typeof x === 'undefined') {
+            x = 1;
+        } else {
+            x = x + 1;
+        }
+      js
+    end
+
+    it 'duplicates the underlying native object' do
+      cxt = V8::Context.new
+
+      cxt.eval(js)
+
+      cloned_cxt = cxt.deep_clone
+
+      cxt.eval(js)
+      cxt["x"].should == 2
+
+      cloned_cxt["x"].should == 1
+      cloned_cxt.eval(js)
+      cloned_cxt["x"].should == 2
+
+      cxt.eval(js)
+      cxt["x"].should == 3
+    end
+
+    it 'works on empty contexts' do
+      cxt = V8::Context.new
+
+      cloned_cxt = cxt.deep_clone
+
+      cxt.eval(js)
+      cxt["x"].should == 1
+
+      cloned_cxt["x"].should be(nil)
+    end
+
+    it 'keeps original options' do
+      cxt = V8::Context.new(:timeout => 10)
+
+      cloned_cxt = cxt.deep_clone
+
+      cloned_cxt.timeout.should == 10
+    end
+
+    context 'when the original context has been disposed of' do
+      it 'should not allow cloning any more' do
+        cxt = V8::Context.new
+
+        cxt.dispose
+
+        lambda { cxt.deep_clone }.should raise_error
+      end
+
+      it 'should not affect previously cloned contexts' do
+        cxt = V8::Context.new
+        cxt.eval(js)
+
+        cloned_cxt = cxt.deep_clone
+
+        cxt.dispose
+
+        cloned_cxt.eval(js)
+        cloned_cxt["x"].should == 2
+      end
+    end
   end
 end