Fabric: Test for reseting (and preserving) Yoga dirty flag during ShadowNode cloning

Summary:
This is a quite fragile and important part of the render engine. We need to dirty Yoga node only in cases where a change affects layout. In the case of over-dirtying, we can kill performance. In the case of under-dirtying, we can produce an incorrect layout.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D19596279

fbshipit-source-id: 9f2ac67c44cb35c8ba44be1025b94b7921b74e17

ReactCommon/fabric/components/view/BUCK

@@ -80,8 +80,9 @@ fb_xplat_cxx_test(
     contacts = ["oncall+react_native@xmail.facebook.com"],
     platforms = (ANDROID, APPLE, CXX),
     deps = [
-        "fbsource//xplat/folly:molly",
         "fbsource//xplat/third-party/gmock:gtest",
-        ":view",
+        react_native_xplat_target("fabric/element:element"),
+        react_native_xplat_target("fabric/components/root:root"),
+        react_native_xplat_target("fabric/components/view:view"),
     ],
 )

ReactCommon/fabric/components/view/tests/ViewTest.cpp

@@ -5,13 +5,176 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+#include <algorithm>
 #include <memory>
 
 #include <gtest/gtest.h>
+
+#include <react/components/root/RootComponentDescriptor.h>
 #include <react/components/view/ViewComponentDescriptor.h>
+#include <react/element/ComponentBuilder.h>
+#include <react/element/Element.h>
+#include <react/element/testUtils.h>
+#include <react/uimanager/ComponentDescriptorProviderRegistry.h>
 
 using namespace facebook::react;
 
-TEST(ViewTest, testSomething) {
-  // TODO
+TEST(ElementTest, testYogaDirtyFlag) {
+  auto builder = simpleComponentBuilder();
+
+  auto rootShadowNode = std::shared_ptr<RootShadowNode>{};
+  auto innerShadowNode = std::shared_ptr<ViewShadowNode>{};
+
+  // clang-format off
+  auto element =
+      Element<RootShadowNode>()
+        .reference(rootShadowNode)
+        .tag(1)
+        .children({
+          Element<ViewShadowNode>()
+            .tag(2),
+          Element<ViewShadowNode>()
+            .tag(3)
+            .reference(innerShadowNode)
+            .children({
+              Element<ViewShadowNode>()
+                .tag(4)
+                .props([] {
+                  /*
+                   * Some non-default props.
+                   */
+                  auto mutableViewProps = std::make_shared<ViewProps>();
+                  auto &props = *mutableViewProps;
+                  props.nativeId = "native Id";
+                  props.opacity = 0.5;
+                  props.yogaStyle.alignContent() = YGAlignBaseline;
+                  props.yogaStyle.flexDirection() = YGFlexDirectionRowReverse;
+                  return mutableViewProps;
+                }),
+              Element<ViewShadowNode>()
+                .tag(5),
+              Element<ViewShadowNode>()
+                .tag(6)
+            })
+        });
+  // clang-format on
+
+  builder.build(element);
+
+  /*
+   * Yoga nodes are dirty right after creation.
+   */
+  EXPECT_TRUE(rootShadowNode->layoutIfNeeded());
+
+  /*
+   * Yoga nodes are clean (not dirty) right after layout pass.
+   */
+  EXPECT_FALSE(rootShadowNode->layoutIfNeeded());
+
+  {
+    /*
+     * Cloning props without changing them must *not* dirty Yoga nodes.
+     */
+    auto newRootShadowNode = rootShadowNode->clone(
+        innerShadowNode->getFamily(), [](ShadowNode const &oldShadowNode) {
+          auto &componentDescriptor = oldShadowNode.getComponentDescriptor();
+          auto props = componentDescriptor.cloneProps(
+              oldShadowNode.getProps(), RawProps());
+          return oldShadowNode.clone(ShadowNodeFragment{props});
+        });
+
+    EXPECT_FALSE(newRootShadowNode->layoutIfNeeded());
+  }
+
+  {
+    /*
+     * Changing *non-layout* sub-props must *not* dirty Yoga nodes.
+     */
+    auto newRootShadowNode = rootShadowNode->clone(
+        innerShadowNode->getFamily(), [](ShadowNode const &oldShadowNode) {
+          auto viewProps = std::make_shared<ViewProps>();
+          auto &props = *viewProps;
+
+          props.nativeId = "some new native Id";
+          props.foregroundColor = whiteColor();
+          props.backgroundColor = blackColor();
+          props.opacity = props.opacity + 0.042;
+          props.zIndex = props.zIndex + 42;
+          props.shouldRasterize = !props.shouldRasterize;
+          props.collapsable = !props.collapsable;
+
+          return oldShadowNode.clone(ShadowNodeFragment{viewProps});
+        });
+
+    EXPECT_FALSE(newRootShadowNode->layoutIfNeeded());
+  }
+
+  {
+    /*
+     * Changing *layout* sub-props *must* dirty Yoga nodes.
+     */
+    auto newRootShadowNode = rootShadowNode->clone(
+        innerShadowNode->getFamily(), [](ShadowNode const &oldShadowNode) {
+          auto viewProps = std::make_shared<ViewProps>();
+          auto &props = *viewProps;
+
+          props.yogaStyle.alignContent() = YGAlignBaseline;
+          props.yogaStyle.display() = YGDisplayNone;
+
+          return oldShadowNode.clone(ShadowNodeFragment{viewProps});
+        });
+
+    EXPECT_TRUE(newRootShadowNode->layoutIfNeeded());
+  }
+
+  {
+    /*
+     * Removing all children *must* dirty Yoga nodes.
+     */
+    auto newRootShadowNode = rootShadowNode->clone(
+        innerShadowNode->getFamily(), [](ShadowNode const &oldShadowNode) {
+          return oldShadowNode.clone(
+              {ShadowNodeFragment::propsPlaceholder(),
+               ShadowNode::emptySharedShadowNodeSharedList()});
+        });
+
+    EXPECT_TRUE(newRootShadowNode->layoutIfNeeded());
+  }
+
+  {
+    /*
+     * Removing the last child *must* dirty Yoga nodes.
+     */
+    auto newRootShadowNode = rootShadowNode->clone(
+        innerShadowNode->getFamily(), [](ShadowNode const &oldShadowNode) {
+          auto children = oldShadowNode.getChildren();
+          children.pop_back();
+
+          std::reverse(children.begin(), children.end());
+
+          return oldShadowNode.clone(
+              {ShadowNodeFragment::propsPlaceholder(),
+               std::make_shared<ShadowNode::ListOfShared const>(children)});
+        });
+
+    EXPECT_TRUE(newRootShadowNode->layoutIfNeeded());
+  }
+
+  {
+    /*
+     * Reversing a list of children *must* dirty Yoga nodes.
+     */
+    auto newRootShadowNode = rootShadowNode->clone(
+        innerShadowNode->getFamily(), [](ShadowNode const &oldShadowNode) {
+          auto children = oldShadowNode.getChildren();
+
+          std::reverse(children.begin(), children.end());
+
+          return oldShadowNode.clone(
+              {ShadowNodeFragment::propsPlaceholder(),
+               std::make_shared<ShadowNode::ListOfShared const>(children)});
+        });
+
+    EXPECT_TRUE(newRootShadowNode->layoutIfNeeded());
+  }
 }

ReactCommon/fabric/element/testUtils.h

@@ -15,7 +15,7 @@
 namespace facebook {
 namespace react {
 
-extern ComponentBuilder simpleComponentBuilder() {
+inline ComponentBuilder simpleComponentBuilder() {
   ComponentDescriptorProviderRegistry componentDescriptorProviderRegistry{};
   auto eventDispatcher = EventDispatcher::Shared{};
   auto componentDescriptorRegistry =