From 42e7cdfc3b97442511f7dac59c84d799dd85f7a2 Mon Sep 17 00:00:00 2001
From: Gerald Versluis <gerald.versluis@microsoft.com>
Date: Fri, 18 Oct 2019 14:03:43 +0200
Subject: [PATCH] [MacOS] Fixed NRE with modal navigation (#7900)

* Added repro and fix

* Added UITest
---
 .../Issue7886.xaml                                 |  9 +++
 .../Issue7886.xaml.cs                              | 74 ++++++++++++++++++++++
 .../Xamarin.Forms.Controls.Issues.Shared.projitems | 12 +++-
 .../VisualElementRenderer.cs                       |  5 +-
 4 files changed, 96 insertions(+), 4 deletions(-)
 create mode 100644 Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml
 create mode 100644 Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml.cs

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml
new file mode 100644
index 0000000..71604d9
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<controls:TestContentPage xmlns:controls="clr-namespace:Xamarin.Forms.Controls" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+	x:Class="Xamarin.Forms.Controls.Issues.Issue7886" >
+	<StackLayout HorizontalOptions="Center" VerticalOptions="Center">
+        <!-- Place new controls here -->
+        <Label Text="Open the modal by the button below, then pop the modal by the Done toolbaritem. If you are back on the first page without a crash, this test succeeded!" HorizontalOptions="Center" VerticalOptions="CenterAndExpand" />
+        <Button AutomationId="{Binding ButtonAutomationId}" Text="Push Me" Clicked="Handle_Clicked" BackgroundColor="Aqua"/>
+    </StackLayout>
+</controls:TestContentPage>
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml.cs
new file mode 100644
index 0000000..7437a32
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7886.xaml.cs
@@ -0,0 +1,74 @@
+using System;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using NUnit.Framework;
+using Xamarin.UITest;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 7886, "PushModalAsync modal page with Entry crashes on close for MacOS (NRE)", PlatformAffected.macOS)]
+	public partial class Issue7886 : TestContentPage
+	{
+
+		const string TriggerModalAutomationId = "TriggerModal";
+		const string PopModalAutomationId = "PopModal";
+
+		public string ButtonAutomationId { get => TriggerModalAutomationId; } 
+
+		protected override void Init()
+		{
+		}
+
+#if APP
+		public Issue7886()
+		{
+			InitializeComponent();
+			BindingContext = this;
+		}
+
+		void Handle_Clicked(object sender, EventArgs e)
+		{
+			Navigation.PushModalAsync(new NavigationPage(new ModalPage()));
+		}
+
+		class ModalPage : ContentPage
+		{
+			public ModalPage()
+			{
+				BackgroundColor = Color.Orange;
+
+				var tbi = new ToolbarItem("Done", null, () => Navigation.PopModalAsync())
+				{
+					AutomationId = PopModalAutomationId
+				};
+
+				ToolbarItems.Add(tbi);
+
+				Content = new Entry
+				{
+					HorizontalOptions = LayoutOptions.Center,
+					VerticalOptions = LayoutOptions.Center
+				};
+			}
+		}
+#endif
+#if UITEST && __MACOS__
+		[Test]
+		public void NoNREOnPushModalAsyncAndBack()
+		{
+			RunningApp.WaitForElement(TriggerModalAutomationId);
+			RunningApp.Tap(TriggerModalAutomationId);
+			RunningApp.WaitForElement(PopModalAutomationId);
+			RunningApp.Tap(PopModalAutomationId);
+		}
+
+		
+#endif
+	}
+
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
index 2676835..b9ffb0f 100644
--- a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
@@ -1116,6 +1116,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue6127.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue7283.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue5395.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue7886.xaml.cs">
+      <DependentUpon>Issue7886.xaml</DependentUpon>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Issue7898.cs" />
   </ItemGroup>
   <ItemGroup>
@@ -1249,6 +1252,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7525.xaml">
       <Generator>UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7886.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla27417Xaml.xaml">
@@ -1531,7 +1537,7 @@
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7593.xaml">
       <SubType>Designer</SubType>
-      <Generator>MSBuild:Compile</Generator>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
@@ -1541,13 +1547,13 @@
     </EmbeddedResource>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7758.xaml">
       <SubType>Designer</SubType>
-      <Generator>MSBuild:Compile</Generator>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7789.xaml">
       <SubType>Designer</SubType>
-      <Generator>MSBuild:Compile</Generator>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
diff --git a/Xamarin.Forms.Platform.iOS/VisualElementRenderer.cs b/Xamarin.Forms.Platform.iOS/VisualElementRenderer.cs
index add6490..2cebe20 100644
--- a/Xamarin.Forms.Platform.iOS/VisualElementRenderer.cs
+++ b/Xamarin.Forms.Platform.iOS/VisualElementRenderer.cs
@@ -283,7 +283,10 @@ namespace Xamarin.Forms.Platform.MacOS
 
 			if (Element != null && !string.IsNullOrEmpty(Element.AutomationId))
 				SetAutomationId(Element.AutomationId);
-			SetAccessibilityLabel();
+
+			if (element != null)
+				SetAccessibilityLabel();
+
 			SetAccessibilityHint();
 			SetIsAccessibilityElement();
 			Performance.Stop(reference);
-- 
2.7.4