Fabric: Equality operators for ShadowNode

Summary: Test for equality will be used in ShadowNode Tree Diffing algorithm.

Reviewed By: fkgozali

Differential Revision: D7467802

fbshipit-source-id: 5383add9fc7d7e4a772ca16e70a54f7e0c36823a

ReactCommon/fabric/core/shadownode/ShadowNode.cpp

@@ -116,6 +116,21 @@ void ShadowNode::clearSourceNode() {
   sourceNode_.reset();
 }
 
+#pragma mark - Equality
+
+bool ShadowNode::operator==(const ShadowNode& rhs) const {
+  // Note: Child nodes are not considered as part of instance's value
+  // and/or identity.
+  return
+    tag_ == rhs.tag_ &&
+    rootTag_ == rhs.rootTag_ &&
+    props_ == rhs.props_;
+}
+
+bool ShadowNode::operator!=(const ShadowNode& rhs) const {
+  return !(*this == rhs);
+}
+
 #pragma mark - DebugStringConvertible
 
 std::string ShadowNode::getDebugName() const {

ReactCommon/fabric/core/shadownode/ShadowNode.h

@@ -67,6 +67,18 @@ public:
   void replaceChild(const SharedShadowNode &oldChild, const SharedShadowNode &newChild);
   void clearSourceNode();
 
+#pragma mark - Equality
+
+  /*
+   * Equality operators.
+   * Use this to compare `ShadowNode`s values for equality (and non-equality).
+   * Same values indicates that nodes must not produce mutation instructions
+   * during tree diffing process.
+   * Child nodes are not considered as part of the value.
+   */
+  virtual bool operator==(const ShadowNode& rhs) const;
+  virtual bool operator!=(const ShadowNode& rhs) const;
+
 #pragma mark - DebugStringConvertible
 
   std::string getDebugName() const override;