Fabric/Text: ShadowNode::clone() - dynamic self-cloning mechanism

Summary:
The previous approach simply didn't work. :(
As you might notice, in previous implementation of ViewShadowNode::cloneAndReplaceChild we used `ViewShadowNode` class for cloning `childNode`, and this is incorrect becasue `childNode` might be instance of any class.

Reviewed By: fkgozali

Differential Revision: D7595016

fbshipit-source-id: 2215414926f2f7a2e2fd05ca2d065f10d6d32b74

ReactCommon/fabric/core/componentdescriptor/ConcreteComponentDescriptor.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <memory>
+#include <functional>
 
 #include <fabric/core/ComponentDescriptor.h>
 #include <fabric/core/Props.h>
@@ -40,7 +41,14 @@ public:
     const InstanceHandle &instanceHandle,
     const SharedProps &props
   ) const override {
-    return std::make_shared<ShadowNodeT>(tag, rootTag, instanceHandle, std::static_pointer_cast<const ConcreteProps>(props));
+    return std::make_shared<ShadowNodeT>(
+      tag,
+      rootTag,
+      instanceHandle,
+      std::static_pointer_cast<const ConcreteProps>(props),
+      ShadowNode::emptySharedShadowNodeSharedList(),
+      getCloneFunction()
+    );
   }
 
   SharedShadowNode cloneShadowNode(
@@ -67,6 +75,18 @@ public:
     return ShadowNodeT::Props(rawProps, props);
   };
 
+private:
+  mutable ShadowNodeCloneFunction cloneFunction_;
+
+  ShadowNodeCloneFunction getCloneFunction() const {
+    if (!cloneFunction_) {
+      cloneFunction_ = [this](const SharedShadowNode &shadowNode, const SharedProps &props, const SharedShadowNodeSharedList &children) {
+        return this->cloneShadowNode(shadowNode, props, children);
+      };
+    }
+
+    return cloneFunction_;
+  }
 };
 
 } // namespace react

ReactCommon/fabric/core/shadownode/ConcreteShadowNode.h

@@ -51,14 +51,16 @@ public:
     const Tag &rootTag,
     const InstanceHandle &instanceHandle,
     const SharedConcreteProps &props = ConcreteShadowNode::defaultSharedProps(),
-    const SharedShadowNodeSharedList &children = ShadowNode::emptySharedShadowNodeSharedList()
+    const SharedShadowNodeSharedList &children = ShadowNode::emptySharedShadowNodeSharedList(),
+    const ShadowNodeCloneFunction &cloneFunction = nullptr
   ):
     ShadowNode(
       tag,
       rootTag,
       instanceHandle,
       (SharedProps)props,
-      children
+      children,
+      cloneFunction
     ) {};
 
   ConcreteShadowNode(

ReactCommon/fabric/core/shadownode/ShadowNode.cpp

@@ -25,13 +25,15 @@ ShadowNode::ShadowNode(
   const Tag &rootTag,
   const InstanceHandle &instanceHandle,
   const SharedProps &props,
-  const SharedShadowNodeSharedList &children
+  const SharedShadowNodeSharedList &children,
+  const ShadowNodeCloneFunction &cloneFunction
 ):
   tag_(tag),
   rootTag_(rootTag),
   instanceHandle_(instanceHandle),
   props_(props),
   children_(std::make_shared<SharedShadowNodeList>(*children)),
+  cloneFunction_(cloneFunction),
   revision_(1) {}
 
 ShadowNode::ShadowNode(
@@ -45,8 +47,17 @@ ShadowNode::ShadowNode(
   props_(props ? props : shadowNode->props_),
   children_(std::make_shared<SharedShadowNodeList>(*(children ? children : shadowNode->children_))),
   sourceNode_(shadowNode),
+  cloneFunction_(shadowNode->cloneFunction_),
   revision_(shadowNode->revision_ + 1) {}
 
+SharedShadowNode ShadowNode::clone(
+  const SharedProps &props,
+  const SharedShadowNodeSharedList &children
+) const {
+  assert(cloneFunction_);
+  return cloneFunction_(shared_from_this(), props_, children_);
+}
+
 #pragma mark - Getters
 
 SharedShadowNodeSharedList ShadowNode::getChildren() const {

ReactCommon/fabric/core/shadownode/ShadowNode.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <string>
+#include <memory>
 #include <vector>
 
 #include <fabric/core/Props.h>
@@ -26,9 +27,12 @@ using SharedShadowNodeSharedList = std::shared_ptr<const SharedShadowNodeList>;
 using SharedShadowNodeUnsharedList = std::shared_ptr<SharedShadowNodeList>;
 using WeakShadowNode = std::weak_ptr<const ShadowNode>;
 
+using ShadowNodeCloneFunction = std::function<SharedShadowNode(SharedShadowNode shadowNode, SharedProps props, SharedShadowNodeSharedList children)>;
+
 class ShadowNode:
   public virtual Sealable,
-  public virtual DebugStringConvertible {
+  public virtual DebugStringConvertible,
+  public std::enable_shared_from_this<ShadowNode> {
 public:
   static SharedShadowNodeSharedList emptySharedShadowNodeSharedList();
 
@@ -39,7 +43,8 @@ public:
     const Tag &rootTag,
     const InstanceHandle &instanceHandle,
     const SharedProps &props = SharedProps(),
-    const SharedShadowNodeSharedList &children = SharedShadowNodeSharedList()
+    const SharedShadowNodeSharedList &children = SharedShadowNodeSharedList(),
+    const ShadowNodeCloneFunction &cloneFunction = nullptr
   );
 
   ShadowNode(
@@ -48,6 +53,14 @@ public:
     const SharedShadowNodeSharedList &children = nullptr
   );
 
+  /*
+   * Clones the shadow node using stored `cloneFunction`.
+   */
+  SharedShadowNode clone(
+    const SharedProps &props = nullptr,
+    const SharedShadowNodeSharedList &children = nullptr
+  ) const;
+
 #pragma mark - Getters
 
   virtual ComponentHandle getComponentHandle() const = 0;
@@ -112,6 +125,12 @@ protected:
 
 private:
 
+  /*
+   * A reference to a cloning function that understands how to clone
+   * the specific type of ShadowNode.
+   */
+  ShadowNodeCloneFunction cloneFunction_;
+
   /*
    * A number of the generation of the ShadowNode instance;
    * is used and useful for debug-printing purposes *only*.

ReactCommon/fabric/core/tests/ShadowNodeTest.cpp

@@ -115,3 +115,38 @@ TEST(ShadowNodeTest, handleSourceNode) {
   ASSERT_EQ(nodeThirdGeneration->getSourceNode(), nodeSecondGeneration);
   ASSERT_EQ(nodeSecondGeneration->getSourceNode(), nodeFirstGeneration);
 }
+
+TEST(ShadowNodeTest, handleCloneFunction) {
+  auto firstNode = std::make_shared<TestShadowNode>(9, 1, (void *)NULL);
+
+  // The shadow node is not clonable if `cloneFunction` is not provided,
+  ASSERT_DEATH_IF_SUPPORTED(firstNode->clone(), "cloneFunction_");
+
+  auto secondNode = std::make_shared<TestShadowNode>(
+    9,
+    1,
+    (void *)NULL,
+    std::make_shared<const TestProps>(),
+    ShadowNode::emptySharedShadowNodeSharedList(),
+    [](const SharedShadowNode &shadowNode, const SharedProps &props, const SharedShadowNodeSharedList &children) {
+      return std::make_shared<const TestShadowNode>(
+        std::static_pointer_cast<const TestShadowNode>(shadowNode),
+        props,
+        children
+      );
+    }
+  );
+
+  auto secondNodeClone = secondNode->clone();
+
+  // Those two nodes are *not* same.
+  ASSERT_NE(secondNode, secondNodeClone);
+
+  // `secondNodeClone` is an instance of `TestShadowNode`.
+  ASSERT_NE(std::dynamic_pointer_cast<const TestShadowNode>(secondNodeClone), nullptr);
+
+  // Both nodes have same content.
+  ASSERT_EQ(secondNode->getTag(), secondNodeClone->getTag());
+  ASSERT_EQ(secondNode->getRootTag(), secondNodeClone->getRootTag());
+  ASSERT_EQ(secondNode->getProps(), secondNodeClone->getProps());
+}

ReactCommon/fabric/view/ViewShadowNode.cpp

@@ -21,14 +21,16 @@ ViewShadowNode::ViewShadowNode(
   const Tag &rootTag,
   const InstanceHandle &instanceHandle,
   const SharedViewProps &props,
-  const SharedShadowNodeSharedList &children
+  const SharedShadowNodeSharedList &children,
+  const ShadowNodeCloneFunction &cloneFunction
 ):
   ConcreteShadowNode(
     tag,
     rootTag,
     instanceHandle,
     props,
-    children
+    children,
+    cloneFunction
   ),
   AccessibleShadowNode(
     props
@@ -92,9 +94,9 @@ SharedLayoutableShadowNodeList ViewShadowNode::getLayoutableChildNodes() const {
 SharedLayoutableShadowNode ViewShadowNode::cloneAndReplaceChild(const SharedLayoutableShadowNode &child) {
   ensureUnsealed();
 
-  auto viewShadowNodeChild = std::dynamic_pointer_cast<const ViewShadowNode>(child);
-  assert(viewShadowNodeChild);
-  auto viewShadowNodeChildClone = std::make_shared<ViewShadowNode>(viewShadowNodeChild);
+  auto childShadowNode = std::dynamic_pointer_cast<const ShadowNode>(child);
+  assert(childShadowNode);
+  auto childShadowNodeClone = childShadowNode->clone();
 
   // This is overloading of `SharedLayoutableShadowNode::cloneAndReplaceChild`,
   // the method is used to clone some node as a preparation for future mutation
@@ -107,10 +109,11 @@ SharedLayoutableShadowNode ViewShadowNode::cloneAndReplaceChild(const SharedLayo
   // In other words, if we don't compensate this change here,
   // the Diffing algorithm will compare wrong trees
   // ("new-but-not-laid-out-yet vs. new" instead of "committed vs. new").
-  viewShadowNodeChildClone->shallowSourceNode();
+  auto nonConstChildShadowNodeClone = std::const_pointer_cast<ShadowNode>(childShadowNodeClone);
+  nonConstChildShadowNodeClone->shallowSourceNode();
 
-  ShadowNode::replaceChild(viewShadowNodeChild, viewShadowNodeChildClone);
-  return std::static_pointer_cast<const LayoutableShadowNode>(viewShadowNodeChildClone);
+  ShadowNode::replaceChild(childShadowNode, childShadowNodeClone);
+  return std::dynamic_pointer_cast<const LayoutableShadowNode>(childShadowNodeClone);
 }
 
 #pragma mark - Equality

ReactCommon/fabric/view/ViewShadowNode.h

@@ -35,7 +35,8 @@ public:
     const Tag &rootTag,
     const InstanceHandle &instanceHandle,
     const SharedViewProps &props = ViewShadowNode::defaultSharedProps(),
-    const SharedShadowNodeSharedList &children = ShadowNode::emptySharedShadowNodeSharedList()
+    const SharedShadowNodeSharedList &children = ShadowNode::emptySharedShadowNodeSharedList(),
+    const ShadowNodeCloneFunction &cloneFunction = nullptr
   );
 
   ViewShadowNode(