From d5f666cbf34391f7faee2fa15bac6b5eb66dd52b Mon Sep 17 00:00:00 2001
From: Michael Comella <michael.l.comella@gmail.com>
Date: Wed, 11 Nov 2020 14:03:50 -0800
Subject: [PATCH] [fenix] For
 https://github.com/mozilla-mobile/fenix/issues/16376: assert num
 ConstraintLayout direct descend RecyclerView.

I'm not convinced this is a useful test because the performance
characteristics seem unfortunately nuanced: if the test fails, it implies
you shouldn't add more but that isn't necessarily true (for example, if
your RV child has a large depth). Furthermore, we haven't measured in a
variety of circumstances that layouts like LinearLayout perform better
as RecyclerView children so maybe it only held for the one small case we
used it in.
---
 .../ui/StartupExcessiveResourceUseTest.kt     | 34 ++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/app/src/androidTest/java/org/mozilla/fenix/ui/StartupExcessiveResourceUseTest.kt b/app/src/androidTest/java/org/mozilla/fenix/ui/StartupExcessiveResourceUseTest.kt
index 82b4be6cf9..7449c05777 100644
--- a/app/src/androidTest/java/org/mozilla/fenix/ui/StartupExcessiveResourceUseTest.kt
+++ b/app/src/androidTest/java/org/mozilla/fenix/ui/StartupExcessiveResourceUseTest.kt
@@ -7,7 +7,9 @@ package org.mozilla.fenix.ui
 import android.util.Log
 import android.view.View
 import android.view.ViewGroup
+import androidx.constraintlayout.widget.ConstraintLayout
 import androidx.core.view.children
+import androidx.recyclerview.widget.RecyclerView
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.uiautomator.UiDevice
 import kotlinx.android.synthetic.main.activity_home.*
@@ -24,6 +26,7 @@ private const val EXPECTED_SUPPRESSION_COUNT = 11
 private const val EXPECTED_RUNBLOCKING_COUNT = 2
 private const val EXPECTED_COMPONENT_INIT_COUNT = 42
 private const val EXPECTED_VIEW_HIERARCHY_DEPTH = 12
+private const val EXPECTED_RECYCLER_VIEW_CONSTRAINT_LAYOUT_CHILDREN = 4
 
 private val failureMsgStrictMode = getErrorMessage(
     shortName = "StrictMode suppression",
@@ -46,6 +49,13 @@ private val failureMsgViewHierarchyDepth = getErrorMessage(
 ) + "Please note that we're not sure if this is a useful metric to assert: with your feedback, " +
     "we'll find out over time if it is or is not."
 
+private val failureMsgRecyclerViewConstraintLayoutChildren = getErrorMessage(
+    shortName = "ConstraintLayout being a common direct descendant of a RecyclerView",
+    implications = "ConstraintLayouts are slow to inflate and are primarily used to flatten deep " +
+        "view hierarchies so can be under-performant as a common RecyclerView child?"
+) + "Please note that we're not sure if this is a useful metric to assert: with your feedback, " +
+    "we'll find out over time if it is or is not."
+
 /**
  * A performance test to limit the number of StrictMode suppressions and number of runBlocking used
  * on startup.
@@ -79,12 +89,20 @@ class StartupExcessiveResourceUseTest {
         val actualSuppresionCount = activityTestRule.activity.components.strictMode.suppressionCount.get().toInt()
         val actualRunBlocking = RunBlockingCounter.count.get()
         val actualComponentInitCount = ComponentInitCount.count.get()
-        val actualViewHierarchyDepth = countAndLogViewHierarchyDepth(activityTestRule.activity.rootContainer, 1)
+
+        val rootView = activityTestRule.activity.rootContainer
+        val actualViewHierarchyDepth = countAndLogViewHierarchyDepth(rootView, 1)
+        val actualRecyclerViewConstraintLayoutChildren = countRecyclerViewConstraintLayoutChildren(rootView, null)
 
         assertEquals(failureMsgStrictMode, EXPECTED_SUPPRESSION_COUNT, actualSuppresionCount)
         assertEquals(failureMsgRunBlocking, EXPECTED_RUNBLOCKING_COUNT, actualRunBlocking)
         assertEquals(failureMsgComponentInit, EXPECTED_COMPONENT_INIT_COUNT, actualComponentInitCount)
         assertEquals(failureMsgViewHierarchyDepth, EXPECTED_VIEW_HIERARCHY_DEPTH, actualViewHierarchyDepth)
+        assertEquals(
+            failureMsgRecyclerViewConstraintLayoutChildren,
+            EXPECTED_RECYCLER_VIEW_CONSTRAINT_LAYOUT_CHILDREN,
+            actualRecyclerViewConstraintLayoutChildren
+        )
     }
 }
 
@@ -101,6 +119,20 @@ private fun countAndLogViewHierarchyDepth(view: View, level: Int): Int {
     }
 }
 
+private fun countRecyclerViewConstraintLayoutChildren(view: View, parent: View?): Int {
+    val viewValue = if (parent is RecyclerView && view is ConstraintLayout) {
+        1
+    } else {
+        0
+    }
+
+    return if (view !is ViewGroup) {
+        viewValue
+    } else {
+        viewValue + view.children.sumBy { countRecyclerViewConstraintLayoutChildren(it, view) }
+    }
+}
+
 private fun getErrorMessage(shortName: String, implications: String) = """$shortName count does not match expected count.
 
     If this PR removed a $shortName call, great! Please decrease the count.