Introducing: Props forwarding whe cloning shadow node

Summary:
Changelog: [internal]

If ShadowNode has not been mounted, forward rawProps from `sourceShadowNode` to newly cloned shadow node.
This is Android specific change, on iOS the logic should remain unchanged.

Reviewed By: JoshuaGross

Differential Revision: D26049264

fbshipit-source-id: 7c201bc2d4e99eec024065714d2172c5c817153c

ReactCommon/react/renderer/core/Constants.cpp

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "Constants.h"
+
+namespace facebook {
+namespace react {
+
+static bool isPropsForwardingEnabled = false;
+
+void Constants::setPropsForwardingEnabled(bool propsForwardingEnabled) {
+  isPropsForwardingEnabled = propsForwardingEnabled;
+}
+
+bool Constants::getPropsForwardingEnabled() {
+  return isPropsForwardingEnabled;
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/react/renderer/core/Constants.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+namespace facebook {
+namespace react {
+
+struct Constants {
+  /*
+      Flag controling props forwarding when shadow node is cloned on Android.
+      Has no effect on iOS.
+  */
+  static void setPropsForwardingEnabled(bool propsForwardingEnabled);
+  static bool getPropsForwardingEnabled();
+};
+
+} // namespace react
+} // namespace facebook

ReactCommon/react/renderer/core/ShadowNode.cpp

@@ -6,6 +6,7 @@
  */
 
 #include "ShadowNode.h"
+#include "Constants.h"
 #include "ShadowNodeFragment.h"
 
 #include <better/small_vector.h>
@@ -24,6 +25,33 @@ SharedShadowNodeSharedList ShadowNode::emptySharedShadowNodeSharedList() {
   return emptySharedShadowNodeSharedList;
 }
 
+/*
+ * On iOS, this method returns `props` if provided, `sourceShadowNode`'s props
+ * otherwise. On Android, we forward props in case `sourceShadowNode` hasn't
+ * been mounted. `Props::rawProps` are merged from `props` to a copy of
+ * `sourceShadowNode.props_` and returned. This is necessary to enable
+ * Background Executor and should be removed once reimplementation of JNI layer
+ * is finished.
+ */
+SharedProps ShadowNode::propsForClonedShadowNode(
+    ShadowNode const &sourceShadowNode,
+    Props::Shared const &props) {
+#ifdef ANDROID
+  if (Constants::getPropsForwardingEnabled()) {
+    bool hasBeenMounted = sourceShadowNode.hasBeenMounted_;
+    bool sourceNodeHasRawProps = !sourceShadowNode.getProps()->rawProps.empty();
+    if (!hasBeenMounted && sourceNodeHasRawProps && props) {
+      auto copiedProps = sourceShadowNode.getProps()->rawProps;
+      copiedProps.merge_patch(props->rawProps);
+      auto &castedProps = const_cast<Props &>(*props);
+      castedProps.rawProps = copiedProps;
+      return props;
+    }
+  }
+#endif
+  return props ? props : sourceShadowNode.getProps();
+}
+
 bool ShadowNode::sameFamily(const ShadowNode &first, const ShadowNode &second) {
   return first.family_ == second.family_;
 }
@@ -60,13 +88,13 @@ ShadowNode::ShadowNode(
 }
 
 ShadowNode::ShadowNode(
-    const ShadowNode &sourceShadowNode,
-    const ShadowNodeFragment &fragment)
+    ShadowNode const &sourceShadowNode,
+    ShadowNodeFragment const &fragment)
     :
 #if RN_DEBUG_STRING_CONVERTIBLE
       revision_(sourceShadowNode.revision_ + 1),
 #endif
-      props_(fragment.props ? fragment.props : sourceShadowNode.props_),
+      props_(propsForClonedShadowNode(sourceShadowNode, fragment.props)),
       children_(
           fragment.children ? fragment.children : sourceShadowNode.children_),
       state_(
@@ -214,6 +242,7 @@ void ShadowNode::cloneChildrenIfShared() {
 void ShadowNode::setMounted(bool mounted) const {
   if (mounted) {
     family_->setMostRecentState(getState());
+    hasBeenMounted_ = mounted;
   }
 
   family_->eventEmitter_->setEnabled(mounted);

ReactCommon/react/renderer/core/ShadowNode.h

@@ -176,8 +176,6 @@ class ShadowNode : public Sealable, public DebugStringConvertible {
    */
   void setMounted(bool mounted) const;
 
-  int getStateRevision() const;
-
 #pragma mark - DebugStringConvertible
 
 #if RN_DEBUG_STRING_CONVERTIBLE
@@ -214,6 +212,12 @@ class ShadowNode : public Sealable, public DebugStringConvertible {
    */
   ShadowNodeFamily::Shared family_;
 
+  mutable std::atomic<bool> hasBeenMounted_{false};
+
+  static SharedProps propsForClonedShadowNode(
+      ShadowNode const &sourceShadowNode,
+      Props::Shared const &props);
+
  protected:
   /*
    * Traits associated with the particular `ShadowNode` class and an instance of

ReactCommon/react/renderer/core/tests/FollyDynamicMergePatchTest.cpp

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <memory>
+
+#include <folly/dynamic.h>
+#include <glog/logging.h>
+#include <gtest/gtest.h>
+
+using namespace folly;
+
+/*
+  Tests that verify expected behaviour from `folly::dynamic::merge_patch`.
+  `merge_patch` is used for props forwarding on Android to enable Background
+  Executor and will be removed once JNI layer is reimplmeneted.
+ */
+TEST(FollyDynamicMergePatchTest, handleNestedObjects) {
+  dynamic map1 = dynamic::object;
+  map1["style"] = dynamic::object("backgroundColor", "red");
+
+  dynamic map2 = dynamic::object;
+  map2["style"] = dynamic::object("backgroundColor", "blue")("color", "black");
+  map2["height"] = 100;
+
+  map2.merge_patch(map1);
+
+  EXPECT_TRUE(map2["style"].isObject());
+  EXPECT_TRUE(map2["style"]["backgroundColor"].isString());
+  EXPECT_TRUE(map2["style"]["color"].isString());
+  EXPECT_TRUE(map2["height"].isInt());
+
+  EXPECT_EQ(map2["style"]["backgroundColor"], "red");
+  EXPECT_EQ(map2["style"]["color"], "black");
+  EXPECT_EQ(map2["height"], 100);
+}
+
+TEST(FollyDynamicMergePatchTest, handleEmptyObject) {
+  dynamic map1 = dynamic::object;
+
+  dynamic map2 = dynamic::object;
+  map2["height"] = 100;
+
+  map2.merge_patch(map1);
+
+  EXPECT_TRUE(map2["height"].isInt());
+  EXPECT_EQ(map2["height"], 100);
+
+  map1.merge_patch(map2);
+
+  EXPECT_TRUE(map1["height"].isInt());
+  EXPECT_EQ(map1["height"], 100);
+}

ReactCommon/react/renderer/scheduler/Scheduler.cpp

@@ -11,6 +11,7 @@
 #include <jsi/jsi.h>
 
 #include <react/renderer/componentregistry/ComponentDescriptorRegistry.h>
+#include <react/renderer/core/Constants.h>
 #include <react/renderer/core/LayoutContext.h>
 #include <react/renderer/debug/SystraceSection.h>
 #include <react/renderer/mounting/MountingOverrideDelegate.h>
@@ -112,6 +113,8 @@ Scheduler::Scheduler(
 #ifdef ANDROID
   removeOutstandingSurfacesOnDestruction_ = reactNativeConfig_->getBool(
       "react_fabric:remove_outstanding_surfaces_on_destruction_android");
+  Constants::setPropsForwardingEnabled(reactNativeConfig_->getBool(
+      "react_fabric:enable_props_forwarding_android"));
 #else
   removeOutstandingSurfacesOnDestruction_ = reactNativeConfig_->getBool(
       "react_fabric:remove_outstanding_surfaces_on_destruction_ios");

packages/rn-tester/Podfile.lock

@@ -798,7 +798,7 @@ SPEC CHECKSUMS:
   CocoaLibEvent: 2fab71b8bd46dd33ddb959f7928ec5909f838e3f
   DoubleConversion: cde416483dac037923206447da6e1454df403714
   FBLazyVector: 91e874a8823933a268c38765a88cbd5dba1fa024
-  FBReactNativeSpec: 9b595c8d6225c3406ac3b61cad0e0dcd9c4ce82c
+  FBReactNativeSpec: f413828a0c0ca7fb738e67dd90281e454d353a46
   Flipper: be611d4b742d8c87fbae2ca5f44603a02539e365
   Flipper-DoubleConversion: 38631e41ef4f9b12861c67d17cb5518d06badc41
   Flipper-Folly: e4493b013c02d9347d5e0cb4d128680239f6c78a