Add weak callback for cleaning the js_object_cache

Author: scottp-dpaw

v8py/context.cpp

@@ -114,6 +114,7 @@ PyObject *context_new(PyTypeObject *type, PyObject *args, PyObject *kwargs) {
 
 void context_dealloc(context_c *self) {
     self->js_context.Reset();
+    PyDict_Clear(self->js_object_cache);
     Py_DECREF(self->js_object_cache);
     Py_DECREF(self->scripts);
     Py_TYPE(self)->tp_free((PyObject *) self);

v8py/pyclass.cpp

@@ -259,9 +259,34 @@ Local<Function> py_class_get_constructor(py_class *self, Local<Context> context)
     return hs.Escape(function);
 }
 
+void py_class_object_weak_callback(const WeakCallbackInfo<Persistent<Object>> &info) {
+    HandleScope hs(isolate);
+    Local<Object> js_object = info.GetParameter()->Get(isolate);
+
+    assert(js_object->GetInternalField(0) == IZ_DAT_OBJECT);
+    PyObject *py_object = (PyObject *) js_object->GetInternalField(1).As<External>()->Value();
+    PyObject *js_object_cache = (PyObject *) js_object->GetInternalField(2).As<External>()->Value();
+
+    if (PyDict_Size(js_object_cache) != 0) {
+        if (PyMapping_HasKey(js_object_cache, py_object)) {
+            PyObject_DelItem(js_object_cache, py_object);
+        }
+    }
+    Py_DECREF(js_object_cache);
+
+    info.GetParameter()->Reset();
+    delete info.GetParameter();
+}
+
+
 void py_class_init_js_object(Local<Object> js_object, PyObject *py_object, Local<Context> context) {
     js_object->SetInternalField(0, IZ_DAT_OBJECT);
     js_object->SetInternalField(1, External::New(isolate, py_object));
+    // the v8::Context will get garbage collected before the JS objects,
+    // so for the weak callback we keep a pointer to the object cache
+    context_c *py_ctx = (context_c *)context->GetEmbedderData(CONTEXT_OBJECT_SLOT).As<External>()->Value();
+    Py_INCREF(py_ctx->js_object_cache);
+    js_object->SetInternalField(2, External::New(isolate, py_ctx->js_object_cache));
 
     // find out if the object is supposed to inherit from Error
     // the information is in an internal field on the last prototype
@@ -280,6 +305,7 @@ void py_class_init_js_object(Local<Object> js_object, PyObject *py_object, Local
     }
 
     Persistent<Object> *obj_handle = new Persistent<Object>(isolate, js_object);
+    obj_handle->SetWeak(obj_handle, py_class_object_weak_callback, WeakCallbackType::kFinalizer);
 
     context_set_cached_jsobject(context, py_object, js_object);
 }