From cc09d21e6047df8378ef3a7a209b68f8d63967a1 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Thu, 17 May 2018 20:03:46 -0700
Subject: [PATCH] Fabric: Simplifying usage of `ConcreteComponentDescriptor`

Summary:
Now ConcreteComponentDescriptor can infer `ComponentName` from `ShadowNodeT` automatically,
so in the most cases we even don't need to create a subclass of that.

Reviewed By: fkgozali

Differential Revision: D8016965

fbshipit-source-id: d910597093c9f4c9f32ca06cb3ef1b12538b9543
---
 .../ConcreteComponentDescriptor.h                 | 15 +++++++++++++++
 .../scrollview/ScrollViewComponentDescriptor.h    |  7 +------
 .../text/paragraph/ParagraphComponentDescriptor.h |  4 ----
 .../text/rawtext/RawTextComponentDescriptor.h     | 10 +---------
 .../fabric/text/text/TextComponentDescriptor.h    |  8 +-------
 ReactCommon/fabric/view/ViewComponentDescriptor.h |  7 +------
 6 files changed, 19 insertions(+), 32 deletions(-)

diff --git a/ReactCommon/fabric/core/componentdescriptor/ConcreteComponentDescriptor.h b/ReactCommon/fabric/core/componentdescriptor/ConcreteComponentDescriptor.h
index f690cb652..3d2721f81 100644
--- a/ReactCommon/fabric/core/componentdescriptor/ConcreteComponentDescriptor.h
+++ b/ReactCommon/fabric/core/componentdescriptor/ConcreteComponentDescriptor.h
@@ -35,6 +35,21 @@ public:
     return typeid(ShadowNodeT).hash_code();
   }
 
+  ComponentName getComponentName() const override {
+    // Even if this looks suboptimal, it is the only way to call
+    // a virtual non-static method of `ShadowNodeT`.
+    // Because it is not a hot path (it is executed once per an app run),
+    // it's fine.
+    return std::make_shared<ShadowNodeT>(
+      0,
+      0,
+      nullptr,
+      std::make_shared<const ConcreteProps>(),
+      ShadowNode::emptySharedShadowNodeSharedList(),
+      nullptr
+    )->ShadowNodeT::getComponentName();
+  }
+
   SharedShadowNode createShadowNode(
     const Tag &tag,
     const Tag &rootTag,
diff --git a/ReactCommon/fabric/scrollview/ScrollViewComponentDescriptor.h b/ReactCommon/fabric/scrollview/ScrollViewComponentDescriptor.h
index 44d61202e..b1c075980 100644
--- a/ReactCommon/fabric/scrollview/ScrollViewComponentDescriptor.h
+++ b/ReactCommon/fabric/scrollview/ScrollViewComponentDescriptor.h
@@ -13,12 +13,7 @@
 namespace facebook {
 namespace react {
 
-class ScrollViewComponentDescriptor final: public ConcreteComponentDescriptor<ScrollViewShadowNode> {
-public:
-  ComponentName getComponentName() const override {
-    return "ScrollView";
-  }
-};
+using ScrollViewComponentDescriptor = ConcreteComponentDescriptor<ScrollViewShadowNode>;
 
 } // namespace react
 } // namespace facebook
diff --git a/ReactCommon/fabric/text/paragraph/ParagraphComponentDescriptor.h b/ReactCommon/fabric/text/paragraph/ParagraphComponentDescriptor.h
index d77676783..6648ddb5e 100644
--- a/ReactCommon/fabric/text/paragraph/ParagraphComponentDescriptor.h
+++ b/ReactCommon/fabric/text/paragraph/ParagraphComponentDescriptor.h
@@ -27,10 +27,6 @@ public:
     textLayoutManager_ = std::make_shared<TextLayoutManager>();
   }
 
-  ComponentName getComponentName() const override {
-    return "Paragraph";
-  }
-
   void adopt(UnsharedShadowNode shadowNode) const override {
     ConcreteComponentDescriptor<ParagraphShadowNode>::adopt(shadowNode);
 
diff --git a/ReactCommon/fabric/text/rawtext/RawTextComponentDescriptor.h b/ReactCommon/fabric/text/rawtext/RawTextComponentDescriptor.h
index 6f615fa3c..ca2ccdbe1 100644
--- a/ReactCommon/fabric/text/rawtext/RawTextComponentDescriptor.h
+++ b/ReactCommon/fabric/text/rawtext/RawTextComponentDescriptor.h
@@ -13,15 +13,7 @@
 namespace facebook {
 namespace react {
 
-/*
- * Descriptor for <RawText> component.
- */
-class RawTextComponentDescriptor: public ConcreteComponentDescriptor<RawTextShadowNode> {
-public:
-  ComponentName getComponentName() const override {
-    return "RawText";
-  }
-};
+using RawTextComponentDescriptor = ConcreteComponentDescriptor<RawTextShadowNode>;
 
 } // namespace react
 } // namespace facebook
diff --git a/ReactCommon/fabric/text/text/TextComponentDescriptor.h b/ReactCommon/fabric/text/text/TextComponentDescriptor.h
index 043492f21..5abb428e3 100644
--- a/ReactCommon/fabric/text/text/TextComponentDescriptor.h
+++ b/ReactCommon/fabric/text/text/TextComponentDescriptor.h
@@ -8,18 +8,12 @@
 #pragma once
 
 #include <fabric/core/ConcreteComponentDescriptor.h>
-#include <fabric/text/TextProps.h>
 #include <fabric/text/TextShadowNode.h>
 
 namespace facebook {
 namespace react {
 
-class TextComponentDescriptor: public ConcreteComponentDescriptor<TextShadowNode> {
-public:
-  ComponentName getComponentName() const override {
-    return "Text";
-  }
-};
+using TextComponentDescriptor = ConcreteComponentDescriptor<TextShadowNode>;
 
 } // namespace react
 } // namespace facebook
diff --git a/ReactCommon/fabric/view/ViewComponentDescriptor.h b/ReactCommon/fabric/view/ViewComponentDescriptor.h
index 1db26dc3b..4c25d8b94 100644
--- a/ReactCommon/fabric/view/ViewComponentDescriptor.h
+++ b/ReactCommon/fabric/view/ViewComponentDescriptor.h
@@ -13,12 +13,7 @@
 namespace facebook {
 namespace react {
 
-class ViewComponentDescriptor: public ConcreteComponentDescriptor<ViewShadowNode> {
-public:
-  ComponentName getComponentName() const override {
-    return "View";
-  }
-};
+using ViewComponentDescriptor = ConcreteComponentDescriptor<ViewShadowNode>;
 
 } // namespace react
 } // namespace facebook