Descriptor clean up

Summary:
1. The base class descriptor was removed, this was given that we have chained descriptor there is no need for this anymore
2. The Base interface node descriptor no longer has a mutable list based api. You simply return a list. The mutable list based api was specifically to allow chaining and this quirk is isoltated to the chained descriptor
3. AbstractChainedDescriptor and ChainedDescriptor were merged

Reviewed By: lblasa

Differential Revision: D39496073

fbshipit-source-id: fb3ec629ec3b27f587bdbd0b323624a4bc4ebea3

android/plugins/litho/src/main/java/com/facebook/flipper/plugins/uidebugger/litho/LithoDescriptors.kt

@@ -8,52 +8,56 @@
 package com.facebook.flipper.plugins.uidebugger.litho
 
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
-import com.facebook.flipper.plugins.uidebugger.descriptors.Descriptor
+import com.facebook.flipper.plugins.uidebugger.descriptors.NodeDescriptor
 import com.facebook.litho.DebugComponent
 import com.facebook.litho.LithoView
 
-object LithoViewDescriptor : Descriptor<LithoView>() {
+object LithoViewDescriptor : NodeDescriptor<LithoView> {
   override fun getId(node: LithoView): String = System.identityHashCode(node).toString()
 
   override fun getName(node: LithoView): String = "LithoView"
 
-  override fun getChildren(node: LithoView, children: MutableList<Any>) {
+  override fun getChildren(node: LithoView): List<Any> {
+    val result = mutableListOf<Any>()
     val debugComponent = DebugComponent.getRootInstance(node)
     if (debugComponent != null) {
-      children.add(debugComponent)
+      result.add(debugComponent)
     }
+    return result
   }
 
   override fun getActiveChild(node: LithoView): Any? = null
 
-  override fun getData(node: LithoView, builder: MutableMap<String, InspectableObject>) {}
+  override fun getData(node: LithoView) = mapOf<String, InspectableObject>()
 }
 
-object DebugComponentDescriptor : Descriptor<DebugComponent>() {
+object DebugComponentDescriptor : NodeDescriptor<DebugComponent> {
   override fun getId(node: DebugComponent): String = System.identityHashCode(node).toString()
 
   override fun getName(node: DebugComponent): String {
     return node.component.simpleName
   }
 
-  // TODO the mutable list thing doesnt make sense for non chained descriptors, should just return
+  override fun getChildren(node: DebugComponent): List<Any> {
-  override fun getChildren(node: DebugComponent, children: MutableList<Any>) {
+    val result = mutableListOf<Any>()
+
     val mountedView = node.mountedView
     val mountedDrawable = node.mountedDrawable
 
     if (mountedView != null) {
-      children.add(mountedView)
+      result.add(mountedView)
     } else if (mountedDrawable != null) {
-      children.add(mountedDrawable)
+      result.add(mountedDrawable)
     } else {
       for (child in node.childComponents) {
-        children.add(child)
+        result.add(child)
       }
     }
+
+    return result
   }
 
   override fun getActiveChild(node: DebugComponent): Any? = null
 
-  // todo same here
+  override fun getData(node: DebugComponent) = mapOf<String, InspectableObject>()
-  override fun getData(node: DebugComponent, builder: MutableMap<String, InspectableObject>) {}
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/LayoutTraversal.kt

@@ -9,9 +9,8 @@ package com.facebook.flipper.plugins.uidebugger.core
 
 import android.util.Log
 import com.facebook.flipper.plugins.uidebugger.LogTag
-import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
-import com.facebook.flipper.plugins.uidebugger.descriptors.Descriptor
 import com.facebook.flipper.plugins.uidebugger.descriptors.DescriptorRegister
+import com.facebook.flipper.plugins.uidebugger.descriptors.NodeDescriptor
 import com.facebook.flipper.plugins.uidebugger.model.Node
 
 class LayoutTraversal(
@@ -19,7 +18,7 @@ class LayoutTraversal(
     val root: ApplicationRef
 ) {
 
-  internal inline fun Descriptor<*>.asAny(): Descriptor<Any> = this as Descriptor<Any>
+  internal inline fun NodeDescriptor<*>.asAny(): NodeDescriptor<Any> = this as NodeDescriptor<Any>
 
   /** Traverses the native android hierarchy */
   fun traverse(): List<Node> {
@@ -36,8 +35,7 @@ class LayoutTraversal(
 
         val descriptor = descriptorRegister.descriptorForClassUnsafe(node::class.java).asAny()
 
-        val children = mutableListOf<Any>()
+        val children = descriptor.getChildren(node)
-        descriptor.getChildren(node, children)
 
         val childrenIds = mutableListOf<String>()
 
@@ -61,8 +59,7 @@ class LayoutTraversal(
               descriptorRegister.descriptorForClassUnsafe(activeChild.javaClass).getId(activeChild)
         }
 
-        val attributes = mutableMapOf<String, InspectableObject>()
+        val attributes = descriptor.getData(node)
-        descriptor.getData(node, attributes)
 
         result.add(
             Node(

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/RootViewResolver.kt

@@ -34,7 +34,7 @@ class RootViewResolver {
   private var viewsField: Field? = null
   private var paramsField: Field? = null
 
-  class RootView(val view: View, val param: WindowManager.LayoutParams)
+  class RootView(val view: View, val param: WindowManager.LayoutParams?)
   interface Listener {
     fun onRootViewAdded(rootView: View)
     fun onRootViewRemoved(rootView: View)
@@ -153,9 +153,9 @@ class RootViewResolver {
         for (i in views.indices) {
           val view = views[i]
           // TODO  FIX, len(param) is not always the same as len(views) For now just use first
-          val param = params[0]
+
           // params
-          roots.add(RootView(view, param))
+          roots.add(RootView(view, null))
         }
       }
     }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/AbstractChainedDescriptor.kt

@@ -1,75 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-package com.facebook.flipper.plugins.uidebugger.descriptors
-
-import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
-
-/**
- * This class derives from Descriptor and provides a canonical implementation of ChainedDescriptor}.
- */
-abstract class AbstractChainedDescriptor<T> : Descriptor<T>(), ChainedDescriptor<T> {
-  private var mSuper: Descriptor<T>? = null
-
-  final override fun setSuper(superDescriptor: Descriptor<T>) {
-    if (superDescriptor !== mSuper) {
-      check(mSuper == null)
-      mSuper = superDescriptor
-    }
-  }
-
-  fun getSuper(): Descriptor<T>? {
-    return mSuper
-  }
-
-  final override fun getActiveChild(node: T): Any? {
-    // ask each descriptor in the chain for an active child, if none available look up the chain
-    // until no more super descriptors
-    return onGetActiveChild(node) ?: mSuper?.getActiveChild(node)
-  }
-
-  /**
-   * A globally unique ID used to identify a node in a hierarchy. If your node does not have a
-   * globally unique ID it is fine to rely on [System.identityHashCode].
-   */
-  final override fun getId(node: T): String {
-    return onGetId(node)
-  }
-
-  abstract fun onGetId(node: T): String
-
-  /**
-   * The name used to identify this node in the inspector. Does not need to be unique. A good
-   * default is to use the class name of the node.
-   */
-  final override fun getName(node: T): String {
-    return onGetName(node)
-  }
-
-  open fun onGetActiveChild(node: T): Any? = null
-
-  abstract fun onGetName(node: T): String
-
-  /** The children this node exposes in the inspector. */
-  final override fun getChildren(node: T, children: MutableList<Any>) {
-    mSuper?.getChildren(node, children)
-    onGetChildren(node, children)
-  }
-
-  open fun onGetChildren(node: T, children: MutableList<Any>) {}
-
-  final override fun getData(node: T, builder: MutableMap<String, InspectableObject>) {
-    mSuper?.getData(node, builder)
-    onGetData(node, builder)
-  }
-
-  /**
-   * Get the data to show for this node in the sidebar of the inspector. Each key will be a have its
-   * own section
-   */
-  open fun onGetData(node: T, attributeSections: MutableMap<String, InspectableObject>) {}
-}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ActivityDescriptor.kt

@@ -11,7 +11,7 @@ import android.app.Activity
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.stetho.FragmentCompat
 
-object ActivityDescriptor : AbstractChainedDescriptor<Activity>() {
+object ActivityDescriptor : ChainedDescriptor<Activity>() {
 
   override fun onGetId(node: Activity): String {
     return System.identityHashCode(node).toString()

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ApplicationRefDescriptor.kt

@@ -13,7 +13,7 @@ import com.facebook.flipper.plugins.uidebugger.LogTag
 import com.facebook.flipper.plugins.uidebugger.core.ApplicationRef
 import com.facebook.flipper.plugins.uidebugger.core.RootViewResolver
 
-object ApplicationRefDescriptor : AbstractChainedDescriptor<ApplicationRef>() {
+object ApplicationRefDescriptor : ChainedDescriptor<ApplicationRef>() {
 
   val rootsLocal = RootViewResolver()
   override fun onGetActiveChild(node: ApplicationRef): Any? {

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ButtonDescriptor.kt

@@ -10,7 +10,7 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 import android.widget.Button
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 
-object ButtonDescriptor : AbstractChainedDescriptor<Button>() {
+object ButtonDescriptor : ChainedDescriptor<Button>() {
 
   override fun onGetId(node: Button): String {
     return System.identityHashCode(node).toString()
@@ -20,5 +20,8 @@ object ButtonDescriptor : AbstractChainedDescriptor<Button>() {
     return node.javaClass.simpleName
   }
 
-  override fun onGetData(node: Button, attributeSections: MutableMap<String, InspectableObject>) {}
+  override fun onGetData(
+      node: Button,
+      attributeSections: MutableMap<SectionName, InspectableObject>
+  ) {}
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ChainedDescriptor.kt

@@ -7,36 +7,94 @@
 
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
+import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
+
 /**
- * This interface marks a Descriptor in a way that is specially understood by the register. When
+ * A chained descriptor is a special type of descriptor that models the inheritance hierarchy in
- * registered for a particular class 'T', a Descriptor that implements this interface will be
+ * native UI frameworks. With this setup you can define a descriptor for each class in the
- * chained (via ChainedDescriptor.setSuper) to the Descriptor that is registered for the super class
+ * inheritance chain and given that we record the super class's descriptor we can automatically
- * of 'T'. If the super class of 'T' doesn't have a registration, then the super-super class will be
+ * aggregate the results for each descriptor in the inheritance hierarchy in a chain.
- * used (and so on). This allows you to implement Descriptor for any class in an inheritance
- * hierarchy without having to couple it (via direct inheritance) to the super-class' Descriptor.
  *
- * To understand why this is useful, let's say you wanted to write a Descriptor for ListView. You
+ * The result is that each descriptor in the inheritance chain only exports the attributes that it
- * have three options:
+ * knows about but we still get all the attributes from the parent classes
- *
- * The first option is to derive directly from Descriptor and write code to describe everything
- * about instances of ListView, including details that are exposed by super classes such as
- * ViewGroup, View, and even Object. This isn't generally a very good choice because it would
- * require a lot of duplicated code amongst many descriptor implementations.
- *
- * The second option is to derive your ListViewDescriptor from ViewGroupDescriptor and only
- * implement code to describe how ListView differs from ViewGroup. This will result in a class
- * hierarchy that is parallel to the one that you are describing, but is also not a good choice for
- * two reasons (let's assume for the moment that ViewGroupDescriptor is deriving from
- * ViewDescriptor). The first problem is that you will need to write code for aggregating results
- * from the super-class in methods such as Descriptor.getChildren and Descriptor.getAttributes. The
- * second problem is that you'd end up with a log of fragility if you ever want to implement a
- * descriptor for classes that are in-between ViewGroup and ListView, e.g. AbsListView. Any
- * descriptor that derived from ViewGroupDescriptor and described a class deriving from AbsListView
- * would have to be modified to now derive from AbsListViewDescriptor.
- *
- * The third option is to implement ChainedDescriptor (e.g. by deriving from
- * AbstractChainedDescriptor) which solves all of these issues for you.
  */
-interface ChainedDescriptor<T> {
+abstract class ChainedDescriptor<T> : NodeDescriptor<T> {
-  fun setSuper(superDescriptor: Descriptor<T>)
+  private var mSuper: ChainedDescriptor<T>? = null
+
+  fun setSuper(superDescriptor: ChainedDescriptor<T>) {
+    if (superDescriptor !== mSuper) {
+      check(mSuper == null)
+      mSuper = superDescriptor
+    }
+  }
+
+  fun getSuper(): ChainedDescriptor<T>? {
+    return mSuper
+  }
+
+  final override fun getActiveChild(node: T): Any? {
+    // ask each descriptor in the chain for an active child, if none available look up the chain
+    // until no more super descriptors
+    return onGetActiveChild(node) ?: mSuper?.getActiveChild(node)
+  }
+
+  /**
+   * A globally unique ID used to identify a node in a hierarchy. If your node does not have a
+   * globally unique ID it is fine to rely on [System.identityHashCode].
+   */
+  final override fun getId(node: T): String {
+    return onGetId(node)
+  }
+
+  abstract fun onGetId(node: T): String
+
+  /**
+   * The name used to identify this node in the inspector. Does not need to be unique. A good
+   * default is to use the class name of the node.
+   */
+  final override fun getName(node: T): String {
+    return onGetName(node)
+  }
+
+  open fun onGetActiveChild(node: T): Any? = null
+
+  abstract fun onGetName(node: T): String
+
+  /** The children this node exposes in the inspector. */
+  final override fun getChildren(node: T): List<Any> {
+    val builder = mutableListOf<Any>()
+    onGetChildren(node, builder)
+
+    var curDescriptor: ChainedDescriptor<T>? = mSuper
+    while (curDescriptor != null) {
+      curDescriptor.onGetChildren(node, builder)
+      curDescriptor = curDescriptor.mSuper
+    }
+
+    return builder
+  }
+
+  // this probably should not be chained as its unlikely you would want children to come from >1
+  // descriptor
+  open fun onGetChildren(node: T, children: MutableList<Any>) {}
+
+  final override fun getData(node: T): Map<SectionName, InspectableObject> {
+    val builder = mutableMapOf<String, InspectableObject>()
+    onGetData(node, builder)
+
+    var curDescriptor: ChainedDescriptor<T>? = mSuper
+
+    while (curDescriptor != null) {
+      curDescriptor.onGetData(node, builder)
+      curDescriptor = curDescriptor.mSuper
+    }
+
+    return builder
+  }
+
+  /**
+   * Get the data to show for this node in the sidebar of the inspector. Each key will be a have its
+   * own section
+   */
+  open fun onGetData(node: T, attributeSections: MutableMap<SectionName, InspectableObject>) {}
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/Descriptor.kt

@@ -1,29 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-package com.facebook.flipper.plugins.uidebugger.descriptors
-
-abstract class Descriptor<T> : NodeDescriptor<T> {
-  var descritorRegister: DescriptorRegister? = null
-  fun setDescriptorRegister(descriptorMapping: DescriptorRegister) {
-    this.descritorRegister = descriptorMapping
-  }
-
-  protected fun descriptorForClass(clazz: Class<*>): Descriptor<*>? {
-    descritorRegister?.let { register ->
-      return register.descriptorForClass(clazz)
-    }
-    return null
-  }
-
-  protected fun descriptorForObject(obj: Any): Descriptor<*>? {
-    descritorRegister?.let { register ->
-      return register.descriptorForClass(obj::class.java)
-    }
-    return null
-  }
-}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/DescriptorRegister.kt

@@ -18,7 +18,7 @@ import com.facebook.flipper.plugins.uidebugger.common.UIDebuggerException
 import com.facebook.flipper.plugins.uidebugger.core.ApplicationRef
 
 class DescriptorRegister {
-  private val register: MutableMap<Class<*>, Descriptor<*>> = HashMap()
+  private val register: MutableMap<Class<*>, NodeDescriptor<*>> = HashMap()
 
   companion object {
 
@@ -35,40 +35,37 @@ class DescriptorRegister {
       mapping.register(ViewPager::class.java, ViewPagerDescriptor)
 
       for (clazz in mapping.register.keys) {
-        val descriptor: Descriptor<*>? = mapping.register[clazz]
+        val descriptor: NodeDescriptor<*>? = mapping.register[clazz]
         descriptor?.let { descriptor ->
           if (descriptor is ChainedDescriptor<*>) {
             val chainedDescriptor = descriptor as ChainedDescriptor<Any>
             val superClass: Class<*> = clazz.getSuperclass()
-            val superDescriptor: Descriptor<*>? = mapping.descriptorForClass(superClass)
+            val superDescriptor: NodeDescriptor<*>? = mapping.descriptorForClass(superClass)
-            superDescriptor?.let { superDescriptor ->
+            // todo we should walk all the way up the superclass hierarchy?
-              chainedDescriptor.setSuper(superDescriptor as Descriptor<Any>)
+            if (superDescriptor is ChainedDescriptor<*>) {
+              chainedDescriptor.setSuper(superDescriptor as ChainedDescriptor<Any>)
             }
           }
         }
       }
 
-      for (descriptor in mapping.register.values) {
-        descriptor.setDescriptorRegister(mapping)
-      }
-
       return mapping
     }
   }
 
-  fun <T> register(clazz: Class<T>, descriptor: Descriptor<T>) {
+  fun <T> register(clazz: Class<T>, descriptor: NodeDescriptor<T>) {
     register[clazz] = descriptor
   }
 
-  fun <T> descriptorForClass(clazz: Class<T>): Descriptor<T>? {
+  fun <T> descriptorForClass(clazz: Class<T>): NodeDescriptor<T>? {
     var clazz: Class<*> = clazz
     while (!register.containsKey(clazz)) {
       clazz = clazz.superclass
     }
-    return register[clazz] as Descriptor<T>
+    return register[clazz] as NodeDescriptor<T>
   }
 
-  fun <T> descriptorForClassUnsafe(clazz: Class<T>): Descriptor<T> {
+  fun <T> descriptorForClassUnsafe(clazz: Class<T>): NodeDescriptor<T> {
     return descriptorForClass(clazz)
         ?: throw UIDebuggerException("No descriptor found for ${clazz.name}")
   }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/NodeDescriptor.kt

@@ -10,12 +10,15 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 
 /*
- Descriptors are an extension point used during traversal to extract data out of arbitary
+ Descriptors are an extension point used during traversal to extract data out of arbitrary
- objects in the hierachy. Descriptors can represent native view or declarative components or
+ objects in the hierarchy. Descriptors can represent native view or declarative components or
  any type of object such as an activity
 
  Descriptors should be stateless and each descriptor should be a singleton
 */
+
+typealias SectionName = String
+
 interface NodeDescriptor<T> {
   /**
    * A globally unique ID used to identify a node in a hierarchy. If your node does not have a
@@ -30,7 +33,7 @@ interface NodeDescriptor<T> {
   fun getName(node: T): String
 
   /** The children this node exposes in the inspector. */
-  fun getChildren(node: T, children: MutableList<Any>)
+  fun getChildren(node: T): List<Any>
 
   /**
    * If you have overlapping children this indicates which child is active / on top, we will only
@@ -42,5 +45,5 @@ interface NodeDescriptor<T> {
    * Get the data to show for this node in the sidebar of the inspector. The object will be shown in
    * order and with a header matching the given name.
    */
-  fun getData(node: T, builder: MutableMap<String, InspectableObject>)
+  fun getData(node: T): Map<SectionName, InspectableObject>
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ObjectDescriptor.kt

@@ -9,7 +9,7 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 
-object ObjectDescriptor : Descriptor<Any>() {
+object ObjectDescriptor : NodeDescriptor<Any> {
 
   override fun getActiveChild(node: Any): Any? = null
 
@@ -21,7 +21,7 @@ object ObjectDescriptor : Descriptor<Any>() {
     return node.javaClass.simpleName
   }
 
-  override fun getChildren(node: Any, children: MutableList<Any>) {}
+  override fun getChildren(node: Any) = listOf<Any>()
 
-  override fun getData(node: Any, builder: MutableMap<String, InspectableObject>) {}
+  override fun getData(node: Any) = mutableMapOf<SectionName, InspectableObject>()
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/TextViewDescriptor.kt

@@ -10,7 +10,7 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 import android.widget.TextView
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 
-object TextViewDescriptor : AbstractChainedDescriptor<TextView>() {
+object TextViewDescriptor : ChainedDescriptor<TextView>() {
 
   override fun onGetId(node: TextView): String {
     return System.identityHashCode(node).toString()
@@ -22,6 +22,6 @@ object TextViewDescriptor : AbstractChainedDescriptor<TextView>() {
 
   override fun onGetData(
       node: TextView,
-      attributeSections: MutableMap<String, InspectableObject>
+      attributeSections: MutableMap<SectionName, InspectableObject>
   ) {}
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ViewDescriptor.kt

@@ -24,7 +24,7 @@ import com.facebook.flipper.plugins.uidebugger.stetho.ResourcesUtil
 import java.lang.reflect.Field
 
 @SuppressLint("DiscouragedPrivateApi")
-object ViewDescriptor : AbstractChainedDescriptor<View>() {
+object ViewDescriptor : ChainedDescriptor<View>() {
 
   override fun onGetId(node: View): String {
     return Integer.toBinaryString(System.identityHashCode(node))
@@ -34,7 +34,10 @@ object ViewDescriptor : AbstractChainedDescriptor<View>() {
     return node.javaClass.simpleName
   }
 
-  override fun onGetData(node: View, attributeSections: MutableMap<String, InspectableObject>) {
+  override fun onGetData(
+      node: View,
+      attributeSections: MutableMap<SectionName, InspectableObject>
+  ) {
     val positionOnScreen = IntArray(2)
     node.getLocationOnScreen(positionOnScreen)
 

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ViewGroupDescriptor.kt

@@ -18,7 +18,7 @@ import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.common.InspectableValue
 import com.facebook.flipper.plugins.uidebugger.stetho.FragmentCompat
 
-object ViewGroupDescriptor : AbstractChainedDescriptor<ViewGroup>() {
+object ViewGroupDescriptor : ChainedDescriptor<ViewGroup>() {
 
   override fun onGetId(node: ViewGroup): String {
     return System.identityHashCode(node).toString()
@@ -41,7 +41,7 @@ object ViewGroupDescriptor : AbstractChainedDescriptor<ViewGroup>() {
 
   override fun onGetData(
       node: ViewGroup,
-      attributeSections: MutableMap<String, InspectableObject>
+      attributeSections: MutableMap<SectionName, InspectableObject>
   ) {
     val viewGroupAttrs = mutableMapOf<String, Inspectable>()
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ViewPagerDescriptor.kt

@@ -9,7 +9,7 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 
 import androidx.viewpager.widget.ViewPager
 
-object ViewPagerDescriptor : AbstractChainedDescriptor<ViewPager>() {
+object ViewPagerDescriptor : ChainedDescriptor<ViewPager>() {
 
   override fun onGetId(node: ViewPager): String = System.identityHashCode(node).toString()
 

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/WindowDescriptor.kt

@@ -9,7 +9,7 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 
 import android.view.Window
 
-object WindowDescriptor : AbstractChainedDescriptor<Window>() {
+object WindowDescriptor : ChainedDescriptor<Window>() {
 
   override fun onGetId(node: Window): String {
     return System.identityHashCode(node).toString()

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/PartialLayoutTraversal.kt

@@ -9,9 +9,8 @@ package com.facebook.flipper.plugins.uidebugger.observers
 
 import android.util.Log
 import com.facebook.flipper.plugins.uidebugger.LogTag
-import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
-import com.facebook.flipper.plugins.uidebugger.descriptors.Descriptor
 import com.facebook.flipper.plugins.uidebugger.descriptors.DescriptorRegister
+import com.facebook.flipper.plugins.uidebugger.descriptors.NodeDescriptor
 import com.facebook.flipper.plugins.uidebugger.model.Node
 
 /**
@@ -24,7 +23,7 @@ class PartialLayoutTraversal(
     private val treeObserverfactory: TreeObserverFactory,
 ) {
 
-  internal fun Descriptor<*>.asAny(): Descriptor<Any> = this as Descriptor<Any>
+  internal fun NodeDescriptor<*>.asAny(): NodeDescriptor<Any> = this as NodeDescriptor<Any>
 
   fun traverse(root: Any): Pair<MutableList<Node>, List<Any>> {
 
@@ -47,8 +46,7 @@ class PartialLayoutTraversal(
 
         val descriptor = descriptorRegister.descriptorForClassUnsafe(node::class.java).asAny()
 
-        val children = mutableListOf<Any>()
+        val children = descriptor.getChildren(node)
-        descriptor.getChildren(node, children)
 
         val childrenIds = mutableListOf<String>()
         val activeChild = descriptor.getActiveChild(node)
@@ -71,8 +69,7 @@ class PartialLayoutTraversal(
               descriptorRegister.descriptorForClassUnsafe(activeChild.javaClass).getId(activeChild)
         }
 
-        val attributes = mutableMapOf<String, InspectableObject>()
+        val attributes = descriptor.getData(node)
-        descriptor.getData(node, attributes)
 
         visited.add(
             Node(

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/TreeObserver.kt

@@ -67,6 +67,9 @@ abstract class TreeObserver<T> {
         children[childKey]!!.cleanUpRecursive()
       }
     }
+
+    // send
+    Log.d(LogTag, "For Observer ${this.type} Sending ${visitedNodes.size} ")
     context.treeObserverManager.send(
         SubtreeUpdate(type, visitedNodes, start, System.currentTimeMillis()))
   }