Removed the ref count work around from classes derived from ReactApplication

change/react-native-windows-2020-04-30-08-22-39-MS_RemoveReactAppRefCountHack.json

@@ -0,0 +1,8 @@
+{
+  "type": "prerelease",
+  "comment": "Removed the ref count work around from classes derived from ReactApplications",
+  "packageName": "react-native-windows",
+  "email": "vmorozov@microsoft.com",
+  "dependentChangeType": "patch",
+  "date": "2020-04-30T15:22:39.524Z"
+}

packages/microsoft-reactnative-sampleapps/windows/SampleAppCPP/App.cpp

@@ -39,11 +39,6 @@ App::App() noexcept {
   PackageProviders().Append(winrt::SampleLibraryCS::ReactPackageProvider());
 
   InitializeComponent();
-
-  // This works around a cpp/winrt bug with composable/aggregable types tracked
-  // by 22116519
-  AddRef();
-  m_inner.as<::IUnknown>()->Release();
 }
 
 } // namespace winrt::SampleAppCpp::implementation

vnext/Microsoft.ReactNative/ReactApplication.cpp

@@ -4,6 +4,7 @@
 #include "pch.h"
 #include "ReactApplication.h"
 #include "ReactApplication.g.cpp"
+
 #include "Modules/LinkingManagerModule.h"
 #include "ReactNativeHost.h"
 
@@ -22,7 +23,16 @@ using namespace xaml::Navigation;
 
 namespace winrt::Microsoft::ReactNative::implementation {
 
-ReactApplication::ReactApplication() noexcept {
+ReactApplication::ReactApplication() = default;
+
+ReactApplication::ReactApplication(IInspectable const &outer) noexcept : ReactApplication{} {
+  // The factory is usually called in the base generated class. We call it here to pass correct
+  // 'outer' interface to enable inheritance from the ReactApplication class in user code.
+  impl::call_factory<xaml::Application, xaml::IApplicationFactory>([&](xaml::IApplicationFactory const &f) {
+    [[maybe_unused]] auto winrt_impl_discarded =
+        f.CreateInstance(outer ? outer : static_cast<IInspectable const &>(*this), this->m_inner);
+  });
+
   Suspending({this, &ReactApplication::OnSuspending});
 
 #if defined _DEBUG && !defined DISABLE_XAML_GENERATED_BREAK_ON_UNHANDLED_EXCEPTION
@@ -111,7 +121,7 @@ void ReactApplication::OnActivated(IActivatedEventArgs const &e) {
 }
 
 void ReactApplication::OnLaunched(LaunchActivatedEventArgs const &e) {
-  Super::OnLaunched(e);
+  base_type::OnLaunched(e);
   // auto args = std::wstring(e.Arguments().c_str());
   this->OnCreate(e);
 }

vnext/Microsoft.ReactNative/ReactApplication.h

@@ -4,15 +4,55 @@
 #pragma once
 
 #include "ReactApplication.g.h"
+#include <CppWinRTIncludes.h>
 #include "ReactNativeHost.h"
 
 namespace winrt::Microsoft::ReactNative::implementation {
 
-struct ReactApplication : ReactApplicationT<ReactApplication> {
-  using Super = ReactApplicationT<ReactApplication>;
+// NoDefaultCtorReactApplication_base is a copy of the generated ReactApplication_base
+// without the default constructor where it calls a factory for the base type.
+// This is done to fix the aggregation issue in types inheriting from the ReactApplication.
+// We call the factory in the ReactApplication constructor where we can pass correct
+// 'outer' interface.
+//
+// This class must match the generated ReactApplication_base.
+// It must be updated if the shape of generated ReactApplication_base is changed in future.
+// The only difference is that this class has no default constructor.
+template <typename D, typename... I>
+struct __declspec(empty_bases) NoDefaultCtorReactApplication_base
+    : implements<
+          D,
+          Microsoft::ReactNative::ReactApplication,
+          composable,
+          composing,
+          xaml::IApplicationOverrides,
+          xaml::IApplicationOverrides2,
+          I...>,
+      impl::require<D, xaml::IApplication, xaml::IApplication2, xaml::IApplication3>,
+      impl::base<D, xaml::Application>,
+      xaml::IApplicationOverridesT<D>,
+      xaml::IApplicationOverrides2T<D> {
+  using base_type = NoDefaultCtorReactApplication_base;
+  using class_type = Microsoft::ReactNative::ReactApplication;
+  using implements_type = typename NoDefaultCtorReactApplication_base::implements_type;
+  using implements_type::implements_type;
+  using composable_base = xaml::Application;
+
+  hstring GetRuntimeClassName() const {
+    return L"Microsoft.ReactNative.ReactApplication";
+  }
 
+ protected:
+  using dispatch = impl::dispatch_to_overridable<D, xaml::IApplicationOverrides, xaml::IApplicationOverrides2>;
+  auto overridable() noexcept {
+    return dispatch::overridable(static_cast<D &>(*this));
+  }
+};
+
+struct ReactApplication : NoDefaultCtorReactApplication_base<ReactApplication> {
  public: // ReactApplication ABI API
-  ReactApplication() noexcept;
+  ReactApplication();
+  ReactApplication(IInspectable const &outer) noexcept;
 
   ReactNative::ReactInstanceSettings InstanceSettings() noexcept;
   void InstanceSettings(ReactNative::ReactInstanceSettings const &value) noexcept;
@@ -57,6 +97,13 @@ struct ReactApplication : ReactApplicationT<ReactApplication> {
 
 namespace winrt::Microsoft::ReactNative::factory_implementation {
 
-struct ReactApplication : ReactApplicationT<ReactApplication, implementation::ReactApplication> {};
+// Override the CreateInstance method to pass baseInterface to the ReactApplication constructor
+// to support correct COM aggregation that is need to inherit from the ReactApplication.
+struct ReactApplication : ReactApplicationT<ReactApplication, implementation::ReactApplication> {
+  auto CreateInstance(IInspectable const &baseInterface, IInspectable &innerInterface) {
+    return impl::composable_factory<implementation::ReactApplication>::template CreateInstance<
+        Microsoft::ReactNative::ReactApplication>(baseInterface, innerInterface, baseInterface);
+  }
+};
 
 } // namespace winrt::Microsoft::ReactNative::factory_implementation

vnext/local-cli/generator-windows/templates/cpp/src/App.cpp

@@ -36,11 +36,6 @@ App::App() noexcept
     REACT_REGISTER_NATIVE_MODULE_PACKAGES(); //code-gen macro from autolink
 
     InitializeComponent();
-
-    // This works around a cpp/winrt bug with composable/aggregable types tracked
-    // by 22116519
-    AddRef();
-    m_inner.as<::IUnknown>()->Release();
 }