From 612f08ed1f18e138ab520dec67a6d1f4cb643c9f Mon Sep 17 00:00:00 2001
From: Oliver Bock <oliver@g7.org>
Date: Mon, 3 Aug 2020 17:12:28 +1000
Subject: [PATCH 1/2] Clean up external object references when they are garbage
 collected, rather than when the context is destroyed.

---
 .../Noesis.Javascript/JavascriptContext.cpp   | 30 +++++++++----------
 Source/Noesis.Javascript/JavascriptContext.h  | 13 ++++----
 .../Noesis.Javascript/JavascriptExternal.cpp  |  9 +++---
 Source/Noesis.Javascript/JavascriptExternal.h |  3 --
 .../Noesis.Javascript/JavascriptInterop.cpp   | 21 ++++++++++---
 5 files changed, 42 insertions(+), 34 deletions(-)

diff --git a/Source/Noesis.Javascript/JavascriptContext.cpp b/Source/Noesis.Javascript/JavascriptContext.cpp
index 2372ebb..73c5fbc 100644
--- a/Source/Noesis.Javascript/JavascriptContext.cpp
+++ b/Source/Noesis.Javascript/JavascriptContext.cpp
@@ -171,8 +171,9 @@ JavascriptContext::JavascriptContext()
 
     isolate->SetFatalErrorHandler(FatalErrorCallback);
 
-	mExternals = gcnew System::Collections::Generic::Dictionary<System::Object ^, WrappedJavascriptExternal>();
     mTypeToConstructorMapping = gcnew System::Collections::Generic::Dictionary<System::Type ^, System::IntPtr>();
+    mTypeToMethods = gcnew System::Collections::Generic::Dictionary<System::Type^, System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^>();
+
 	mFunctions = gcnew System::Collections::Generic::List<System::WeakReference ^>();
 	HandleScope scope(isolate);
 	mContext = new Persistent<Context>(isolate, Context::New(isolate));
@@ -186,8 +187,6 @@ JavascriptContext::~JavascriptContext()
 	{
 		v8::Locker v8ThreadLock(isolate);
 		v8::Isolate::Scope isolate_scope(isolate);
-		for each (WrappedJavascriptExternal wrapped in mExternals->Values)
-			delete wrapped.Pointer;
         for each (System::WeakReference^ f in mFunctions) {
             JavascriptFunction ^function = safe_cast<JavascriptFunction ^>(f->Target);
             if (function != nullptr)
@@ -197,8 +196,8 @@ JavascriptContext::~JavascriptContext()
             delete (void *)p;
         }
 		delete mContext;
-		delete mExternals;
         delete mTypeToConstructorMapping;
+        delete mTypeToMethods;
 		delete mFunctions;
 	}
 	if (isolate != NULL)
@@ -298,6 +297,7 @@ void JavascriptContext::SetConstructor(System::String^ name, System::Type^ assoc
     functionTemplate->SetClassName(className);
     JavascriptInterop::InitObjectWrapperTemplate(functionTemplate->InstanceTemplate());
     mTypeToConstructorMapping[associatedType] = System::IntPtr(new Persistent<FunctionTemplate>(isolate, functionTemplate));
+    mTypeToMethods[associatedType] = gcnew System::Collections::Generic::Dictionary<System::String^, WrappedMethod>();
     Local<Context>::New(isolate, *mContext)->Global()->Set(context, className, functionTemplate->GetFunction(context).ToLocalChecked());
 }
 
@@ -505,18 +505,7 @@ JavascriptContext::Collect()
 JavascriptExternal*
 JavascriptContext::WrapObject(System::Object^ iObject)
 {
-	WrappedJavascriptExternal external_wrapped;
-	if (mExternals->TryGetValue(iObject, external_wrapped))
-	{
-		// We've wrapped this guy before.
-		return external_wrapped.Pointer;
-	}
-	else
-	{
-		JavascriptExternal* external = new JavascriptExternal(iObject);
-		mExternals[iObject] = WrappedJavascriptExternal(external);
-		return external;
-	}
+    return new JavascriptExternal(iObject);
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -529,6 +518,7 @@ JavascriptContext::GetObjectWrapperConstructorTemplate(System::Type ^type)
         Local<FunctionTemplate> constructor = FunctionTemplate::New(GetCurrentIsolate());
         JavascriptInterop::InitObjectWrapperTemplate(constructor->InstanceTemplate());
         mTypeToConstructorMapping[type] = System::IntPtr(new Persistent<FunctionTemplate>(isolate, constructor));
+        mTypeToMethods[type] = gcnew System::Collections::Generic::Dictionary<System::String^, WrappedMethod>();
         return constructor;
     }
     Persistent<FunctionTemplate> *constructor = (Persistent<FunctionTemplate> *)(void *)ptrToConstructor;
@@ -537,6 +527,14 @@ JavascriptContext::GetObjectWrapperConstructorTemplate(System::Type ^type)
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^
+JavascriptContext::MethodsForType(System::Type^ type)
+{
+    return mTypeToMethods[type];
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 void
 JavascriptContext::RegisterFunction(System::Object^ f)
 {
diff --git a/Source/Noesis.Javascript/JavascriptContext.h b/Source/Noesis.Javascript/JavascriptContext.h
index 553a6c8..4c40c91 100644
--- a/Source/Noesis.Javascript/JavascriptContext.h
+++ b/Source/Noesis.Javascript/JavascriptContext.h
@@ -94,6 +94,7 @@ public value struct WrappedJavascriptExternal
 {
 private:
 	System::IntPtr pointer;
+    System::Type^ type;
 
 internal:
 	WrappedJavascriptExternal(JavascriptExternal *value)
@@ -196,6 +197,8 @@ public ref class JavascriptContext: public System::IDisposable
 
 	Local<FunctionTemplate> GetObjectWrapperConstructorTemplate(System::Type ^type);
 
+    System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^ MethodsForType(System::Type^ type);
+
 	void RegisterFunction(System::Object^ f);
 
 	static void FatalErrorCallbackMember(const char* location, const char* message);
@@ -212,18 +215,16 @@ public ref class JavascriptContext: public System::IDisposable
 	// v8 context required to be active for all v8 operations.
 	Persistent<Context>* mContext;
 
-	// Stores every JavascriptExternal we create.  This saves time if the same
-	// objects are recreated frequently, and stops us building up a huge
-	// collection of JavascriptExternal objects that won't be freed until
-	// the context is destroyed.
-	System::Collections::Generic::Dictionary<System::Object ^, WrappedJavascriptExternal> ^mExternals;
-
     // Maps types to their constructor function templates
     // The mapping will either be defined by the user calling `SetConstructor` or autogenerated if no
     // mapping was provided.
     // The `IntPtr` points to a `Persistent<FunctionTemplate>`.
     System::Collections::Generic::Dictionary<System::Type ^, System::IntPtr> ^mTypeToConstructorMapping;
 
+    // For each distinct CLR type we've wrapped, this accumulates functions
+    // constructed to access its methods/properties.
+    System::Collections::Generic::Dictionary<System::Type ^, System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^>^ mTypeToMethods;
+
 	// Stores every JavascriptFunction we create.  Ensures we dispose of them
 	// all.
 	System::Collections::Generic::List<System::WeakReference ^> ^mFunctions;
diff --git a/Source/Noesis.Javascript/JavascriptExternal.cpp b/Source/Noesis.Javascript/JavascriptExternal.cpp
index 378ffdb..79aa35b 100644
--- a/Source/Noesis.Javascript/JavascriptExternal.cpp
+++ b/Source/Noesis.Javascript/JavascriptExternal.cpp
@@ -52,7 +52,6 @@ JavascriptExternal::JavascriptExternal(System::Object^ iObject)
 {
 	mObjectHandle = System::Runtime::InteropServices::GCHandle::Alloc(iObject);
 	mOptions = SetParameterOptions::None;
-	mMethods = gcnew System::Collections::Generic::Dictionary<System::String ^, WrappedMethod>();
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -76,15 +75,16 @@ Local<Function>
 JavascriptExternal::GetMethod(wstring iName)
 {
 	v8::Isolate *isolate = JavascriptContext::GetCurrentIsolate();
-	System::Collections::Generic::Dictionary<System::String ^, WrappedMethod> ^methods = mMethods;
+    JavascriptContext^ context = JavascriptContext::GetCurrent();
+    System::Object^ self = mObjectHandle.Target;
+    System::Type^ type = self->GetType();
+    System::Collections::Generic::Dictionary<System::String ^, WrappedMethod> ^methods = context->MethodsForType(type);
 	System::String^ memberName = gcnew System::String(iName.c_str());
 	WrappedMethod method;
 	if (methods->TryGetValue(memberName, method))
 		return Local<Function>::New(isolate, *(method.Pointer));
 	else
 	{
-		System::Object^ self = mObjectHandle.Target;
-		System::Type^ type = self->GetType();
 		System::String^ memberName = gcnew System::String(iName.c_str());
 		cli::array<System::Object^>^ objectInfo = gcnew cli::array<System::Object^>(2);
 		objectInfo->SetValue(self,0);
@@ -94,7 +94,6 @@ JavascriptExternal::GetMethod(wstring iName)
 		cli::array<MemberInfo^>^ members = type->GetMember(memberName);
 		if (members->Length > 0 && members[0]->MemberType == MemberTypes::Method)
 		{
-			JavascriptContext^ context = JavascriptContext::GetCurrent();
 			Local<External> external = External::New(isolate, context->WrapObject(objectInfo));
 			Local<FunctionTemplate> functionTemplate = FunctionTemplate::New(isolate, JavascriptInterop::Invoker, external);
 			Local<Function> function = functionTemplate->GetFunction(isolate->GetCurrentContext()).ToLocalChecked();
diff --git a/Source/Noesis.Javascript/JavascriptExternal.h b/Source/Noesis.Javascript/JavascriptExternal.h
index 6eaf995..566aa21 100644
--- a/Source/Noesis.Javascript/JavascriptExternal.h
+++ b/Source/Noesis.Javascript/JavascriptExternal.h
@@ -98,9 +98,6 @@ class JavascriptExternal
 
 	SetParameterOptions mOptions;
 
-	// Owned by JavascriptContext.
-	gcroot<System::Collections::Generic::Dictionary<System::String ^, WrappedMethod> ^> mMethods;
-
     std::unique_ptr<Persistent<Function>> mIterator;
     static void IteratorCallback(const v8::FunctionCallbackInfo<Value>& iArgs);
     static void IteratorNextCallback(const v8::FunctionCallbackInfo<Value>& iArgs);
diff --git a/Source/Noesis.Javascript/JavascriptInterop.cpp b/Source/Noesis.Javascript/JavascriptInterop.cpp
index 89af423..98cf5fa 100644
--- a/Source/Noesis.Javascript/JavascriptInterop.cpp
+++ b/Source/Noesis.Javascript/JavascriptInterop.cpp
@@ -259,7 +259,14 @@ JavascriptInterop::ConvertToV8(System::Object^ iObject)
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-// TODO: should return Local<External>
+// a sort-of destructor in v8 land
+void JavascriptExternalMakeWeak(const v8::WeakCallbackInfo<JavascriptExternal>& data) {
+    v8::Isolate* isolate = JavascriptContext::GetCurrentIsolate();
+    JavascriptExternal *external = data.GetParameter();
+    delete external;
+}
+
+// TO DO: should return Local<External>
 Local<Object>
 JavascriptInterop::WrapObject(System::Object^ iObject)
 {
@@ -267,11 +274,17 @@ JavascriptInterop::WrapObject(System::Object^ iObject)
 
 	if (context != nullptr)
 	{
-		Local<FunctionTemplate> templ = context->GetObjectWrapperConstructorTemplate(iObject->GetType());
+        System::Type ^object_type = iObject->GetType();
+		Local<FunctionTemplate> templ = context->GetObjectWrapperConstructorTemplate(object_type);
 		v8::Isolate *isolate = JavascriptContext::GetCurrentIsolate();
         Local<ObjectTemplate> instanceTemplate = templ->InstanceTemplate();
 		Local<Object> object = instanceTemplate->NewInstance(isolate->GetCurrentContext()).ToLocalChecked();
-		object->SetInternalField(0, External::New(isolate, context->WrapObject(iObject)));
+        JavascriptExternal* external = context->WrapObject(iObject);
+		object->SetInternalField(0, External::New(isolate, external));
+        
+        // So we're notified when this object is no longer needed.
+        v8::Persistent<v8::Object, v8::CopyablePersistentTraits<v8::Object>> pobj(isolate, object);
+        pobj.SetWeak<JavascriptExternal>(external, JavascriptExternalMakeWeak, v8::WeakCallbackType::kParameter);
 
 		return object;
 	}
@@ -281,7 +294,7 @@ JavascriptInterop::WrapObject(System::Object^ iObject)
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-// TODO: should use Local<External> iExternal
+// TO DO: should use Local<External> iExternal
 System::Object^
 JavascriptInterop::UnwrapObject(Local<Value> iValue)
 {

From f5de7b8d5cb96c1f88755f26f1a6d4108d6491b2 Mon Sep 17 00:00:00 2001
From: Oliver Bock <oliver@g7.org>
Date: Wed, 5 Aug 2020 12:01:08 +1000
Subject: [PATCH 2/2] Cache dictionary of methods with JavaScriptExternal to
 make Getter() faster.

---
 .../Noesis.Javascript/JavascriptContext.cpp   |  2 +-
 Source/Noesis.Javascript/JavascriptContext.h  |  3 +--
 .../Noesis.Javascript/JavascriptExternal.cpp  | 21 +++++++++++--------
 Source/Noesis.Javascript/JavascriptExternal.h |  5 ++++-
 .../Noesis.Javascript/JavascriptInterop.cpp   |  2 +-
 5 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/Source/Noesis.Javascript/JavascriptContext.cpp b/Source/Noesis.Javascript/JavascriptContext.cpp
index 73c5fbc..06ff19d 100644
--- a/Source/Noesis.Javascript/JavascriptContext.cpp
+++ b/Source/Noesis.Javascript/JavascriptContext.cpp
@@ -505,7 +505,7 @@ JavascriptContext::Collect()
 JavascriptExternal*
 JavascriptContext::WrapObject(System::Object^ iObject)
 {
-    return new JavascriptExternal(iObject);
+    return new JavascriptExternal(iObject, false);
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/Source/Noesis.Javascript/JavascriptContext.h b/Source/Noesis.Javascript/JavascriptContext.h
index 4c40c91..8e81d0b 100644
--- a/Source/Noesis.Javascript/JavascriptContext.h
+++ b/Source/Noesis.Javascript/JavascriptContext.h
@@ -94,7 +94,6 @@ public value struct WrappedJavascriptExternal
 {
 private:
 	System::IntPtr pointer;
-    System::Type^ type;
 
 internal:
 	WrappedJavascriptExternal(JavascriptExternal *value)
@@ -199,7 +198,7 @@ public ref class JavascriptContext: public System::IDisposable
 
     System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^ MethodsForType(System::Type^ type);
 
-	void RegisterFunction(System::Object^ f);
+    void RegisterFunction(System::Object^ f);
 
 	static void FatalErrorCallbackMember(const char* location, const char* message);
 
diff --git a/Source/Noesis.Javascript/JavascriptExternal.cpp b/Source/Noesis.Javascript/JavascriptExternal.cpp
index 79aa35b..ddbbaa4 100644
--- a/Source/Noesis.Javascript/JavascriptExternal.cpp
+++ b/Source/Noesis.Javascript/JavascriptExternal.cpp
@@ -48,10 +48,13 @@ using namespace std;
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-JavascriptExternal::JavascriptExternal(System::Object^ iObject)
+JavascriptExternal::JavascriptExternal(System::Object^ iObject, bool needs_methods)
 {
 	mObjectHandle = System::Runtime::InteropServices::GCHandle::Alloc(iObject);
 	mOptions = SetParameterOptions::None;
+    System::Type^ type = iObject->GetType();
+    if (needs_methods)
+        mMethods = JavascriptContext::GetCurrent()->MethodsForType(type);
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -75,17 +78,16 @@ Local<Function>
 JavascriptExternal::GetMethod(wstring iName)
 {
 	v8::Isolate *isolate = JavascriptContext::GetCurrentIsolate();
-    JavascriptContext^ context = JavascriptContext::GetCurrent();
-    System::Object^ self = mObjectHandle.Target;
-    System::Type^ type = self->GetType();
-    System::Collections::Generic::Dictionary<System::String ^, WrappedMethod> ^methods = context->MethodsForType(type);
-	System::String^ memberName = gcnew System::String(iName.c_str());
+    System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^ methods = mMethods;
+    System::String^ memberName = gcnew System::String(iName.c_str());
 	WrappedMethod method;
 	if (methods->TryGetValue(memberName, method))
 		return Local<Function>::New(isolate, *(method.Pointer));
 	else
 	{
-		System::String^ memberName = gcnew System::String(iName.c_str());
+        System::Object^ self = mObjectHandle.Target;
+        System::Type^ type = self->GetType();
+        System::String^ memberName = gcnew System::String(iName.c_str());
 		cli::array<System::Object^>^ objectInfo = gcnew cli::array<System::Object^>(2);
 		objectInfo->SetValue(self,0);
 		objectInfo->SetValue(memberName,1);
@@ -94,13 +96,14 @@ JavascriptExternal::GetMethod(wstring iName)
 		cli::array<MemberInfo^>^ members = type->GetMember(memberName);
 		if (members->Length > 0 && members[0]->MemberType == MemberTypes::Method)
 		{
-			Local<External> external = External::New(isolate, context->WrapObject(objectInfo));
+            JavascriptContext^ context = JavascriptContext::GetCurrent();
+            Local<External> external = External::New(isolate, context->WrapObject(objectInfo));
 			Local<FunctionTemplate> functionTemplate = FunctionTemplate::New(isolate, JavascriptInterop::Invoker, external);
 			Local<Function> function = functionTemplate->GetFunction(isolate->GetCurrentContext()).ToLocalChecked();
 
 			Persistent<Function> *function_ptr = new Persistent<Function>(isolate, function);
 			WrappedMethod wrapped(function_ptr);
-			methods[memberName] = wrapped;
+            methods[memberName] = wrapped;
 
 			return function;
 		}
diff --git a/Source/Noesis.Javascript/JavascriptExternal.h b/Source/Noesis.Javascript/JavascriptExternal.h
index 566aa21..5beaaca 100644
--- a/Source/Noesis.Javascript/JavascriptExternal.h
+++ b/Source/Noesis.Javascript/JavascriptExternal.h
@@ -57,7 +57,7 @@ class JavascriptExternal
 	////////////////////////////////////////////////////////////
 public:
 
-	JavascriptExternal(System::Object^ iObject);
+	JavascriptExternal(System::Object^ iObject, bool needs_methods);
 
 	~JavascriptExternal();
 
@@ -98,6 +98,9 @@ class JavascriptExternal
 
 	SetParameterOptions mOptions;
 
+    // Owned by JavascriptContext.  Only set when the object is with `JavascriptInterop::Getter()`
+    gcroot<System::Collections::Generic::Dictionary<System::String^, WrappedMethod>^> mMethods;
+
     std::unique_ptr<Persistent<Function>> mIterator;
     static void IteratorCallback(const v8::FunctionCallbackInfo<Value>& iArgs);
     static void IteratorNextCallback(const v8::FunctionCallbackInfo<Value>& iArgs);
diff --git a/Source/Noesis.Javascript/JavascriptInterop.cpp b/Source/Noesis.Javascript/JavascriptInterop.cpp
index 98cf5fa..1b354be 100644
--- a/Source/Noesis.Javascript/JavascriptInterop.cpp
+++ b/Source/Noesis.Javascript/JavascriptInterop.cpp
@@ -279,7 +279,7 @@ JavascriptInterop::WrapObject(System::Object^ iObject)
 		v8::Isolate *isolate = JavascriptContext::GetCurrentIsolate();
         Local<ObjectTemplate> instanceTemplate = templ->InstanceTemplate();
 		Local<Object> object = instanceTemplate->NewInstance(isolate->GetCurrentContext()).ToLocalChecked();
-        JavascriptExternal* external = context->WrapObject(iObject);
+        JavascriptExternal* external = new JavascriptExternal(iObject, true);
 		object->SetInternalField(0, External::New(isolate, external));
         
         // So we're notified when this object is no longer needed.

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