From 20ebb83b47ecee1c8ef914895c6e3246929b362b Mon Sep 17 00:00:00 2001
From: Liu Bing <liubinging@gmail.com>
Date: Wed, 31 Oct 2018 21:06:33 -0700
Subject: [PATCH 1/2] Fix a recycling bug that purges indirect subviews

Only walk first level of subviews that are created by LayoutKit.
If a subview isn't created by LayoutKit, then there is no need to walk
subviews of it, as they must not be created by this layout.
---
 LayoutKitTests/ViewRecyclerTests.swift | 24 ++++++++++++++++++++++++
 Sources/ViewRecycler.swift             |  8 ++++++--
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/LayoutKitTests/ViewRecyclerTests.swift b/LayoutKitTests/ViewRecyclerTests.swift
index 8fd291ad..994129d6 100644
--- a/LayoutKitTests/ViewRecyclerTests.swift
+++ b/LayoutKitTests/ViewRecyclerTests.swift
@@ -91,6 +91,30 @@ class ViewRecyclerTests: XCTestCase {
         XCTAssertNotNil(one.superview)
     }
 
+    func testRecycledViewWithoutPurgingIndirectSubviews() {
+        let root = View()
+        let headerView = View()
+        headerView.isLayoutKitView = true
+        root.addSubview(headerView)
+        let titleView = View(viewReuseId: "1")
+        root.addSubview(titleView)
+        let collectionView = View()
+        let cellView = View()
+        cellView.isLayoutKitView = true
+        root.addSubview(collectionView)
+        collectionView.addSubview(cellView)
+
+        let recycler = ViewRecycler(rootView: root)
+        let _ = recycler.makeOrRecycleView(havingViewReuseId: nil, viewProvider: {
+            return View()
+        })
+
+        recycler.purgeViews()
+        XCTAssertNil(headerView.superview)
+        XCTAssertNil(titleView.superview)
+        XCTAssertNotNil(cellView.superview)
+    }
+
     #if os(iOS) || os(tvOS)
     /// Test that a reused view's frame shouldn't change if its transform and layer anchor point
     /// get set to the default values.
diff --git a/Sources/ViewRecycler.swift b/Sources/ViewRecycler.swift
index c9df554c..81692311 100644
--- a/Sources/ViewRecycler.swift
+++ b/Sources/ViewRecycler.swift
@@ -28,15 +28,19 @@ class ViewRecycler {
     private let defaultTransform = CGAffineTransform.identity
     #endif
 
-    /// Retains all subviews of rootView for recycling.
+    /// Retains all LayoutKit subviews of rootView for recycling.
     init(rootView: View?) {
-        rootView?.walkSubviews { (view) in
+        let visitor: (View) -> Void = { view in
             if let viewReuseId = view.viewReuseId {
                 self.viewsById[viewReuseId] = view
             } else {
                 self.unidentifiedViews.insert(view)
             }
         }
+        rootView?.subviews.filter({$0.isLayoutKitView || $0.viewReuseId != nil}).forEach { (view) in
+            visitor(view)
+            view.walkSubviews(visitor: visitor)
+        }
     }
 
     /**

From 15b510a0f01babc2f771e99206d5bf30a6db8a43 Mon Sep 17 00:00:00 2001
From: Liu Bing <liubinging@gmail.com>
Date: Thu, 1 Nov 2018 20:07:50 -0700
Subject: [PATCH 2/2] Check LayoutKitView at every level.

Fix test failures in ViewRecyclerTests.
Add comments for the change.
---
 LayoutKitTests/ViewRecyclerTests.swift |  2 ++
 Sources/ViewRecycler.swift             | 15 ++++++++-------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/LayoutKitTests/ViewRecyclerTests.swift b/LayoutKitTests/ViewRecyclerTests.swift
index 994129d6..311323b7 100644
--- a/LayoutKitTests/ViewRecyclerTests.swift
+++ b/LayoutKitTests/ViewRecyclerTests.swift
@@ -172,5 +172,7 @@ extension View {
     convenience init(viewReuseId: String) {
         self.init(frame: .zero)
         self.viewReuseId = viewReuseId
+        // All views created in the ViewRecycler should be marked as LayoutKitView.
+        self.isLayoutKitView = true
     }
 }
diff --git a/Sources/ViewRecycler.swift b/Sources/ViewRecycler.swift
index 81692311..af27e456 100644
--- a/Sources/ViewRecycler.swift
+++ b/Sources/ViewRecycler.swift
@@ -30,17 +30,13 @@ class ViewRecycler {
 
     /// Retains all LayoutKit subviews of rootView for recycling.
     init(rootView: View?) {
-        let visitor: (View) -> Void = { view in
+        rootView?.walkSubviews { (view) in
             if let viewReuseId = view.viewReuseId {
                 self.viewsById[viewReuseId] = view
             } else {
                 self.unidentifiedViews.insert(view)
             }
         }
-        rootView?.subviews.filter({$0.isLayoutKitView || $0.viewReuseId != nil}).forEach { (view) in
-            visitor(view)
-            view.walkSubviews(visitor: visitor)
-        }
     }
 
     /**
@@ -112,9 +108,14 @@ private var isLayoutKitViewKey: UInt8 = 0
 
 extension View {
 
-    /// Calls visitor for each transitive subview.
+    /// Calls visitor for each transitive LayoutKit subview.
     func walkSubviews(visitor: (View) -> Void) {
-        for subview in subviews {
+        /*
+         Fix a recycling bug that purges indirect subviews by only walking subviews that are created by LayoutKit.
+         If a subview isn't a LayoutKit subview, then there is no need to walk subviews of it,
+         as they must not be created by this layout.
+         */
+        for subview in subviews where subview.isLayoutKitView {
             visitor(subview)
             subview.walkSubviews(visitor: visitor)
         }