From f289f98f3ab6e7204a2537ba7e2716ffc4f9d261 Mon Sep 17 00:00:00 2001
From: Maxim Lipnin <v-maxlip@microsoft.com>
Date: Mon, 12 Jul 2021 15:25:17 +0300
Subject: [PATCH 1/4] Use ReflectionOnly as data contract serializer option for
 iOS/tvOS/MacCatalyst

---
 .../Serialization/DataContractSerializer.cs   | 12 +++++++-
 .../XmlFormatWriterGeneratorAOT/Program.cs    | 30 +++++++++++++++++++
 ...or.XmlFormatWriterGeneratorAot.Test.csproj | 19 ++++++++++++
 3 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/Program.cs
 create mode 100644 src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/iOS.Simulator.XmlFormatWriterGeneratorAot.Test.csproj

diff --git a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
index 71f4530f4f3d1..7ec3793d7bd18 100644
--- a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
+++ b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
@@ -34,7 +34,17 @@ public sealed class DataContractSerializer : XmlObjectSerializer
         private ISerializationSurrogateProvider? _serializationSurrogateProvider;
         private bool _serializeReadOnlyTypes;
 
-        private static SerializationOption _option = IsReflectionBackupAllowed() ? SerializationOption.ReflectionAsBackup : SerializationOption.CodeGenOnly;
+        private static SerializationOption _option = SetSerializationOption();
+
+        private static SerializationOption SetSerializationOption()
+        {
+            if (OperatingSystem.IsIOS() || OperatingSystem.IsTvOS() || OperatingSystem.IsMacCatalyst())
+            {
+                return SerializationOption.ReflectionOnly;
+            }
+
+            return IsReflectionBackupAllowed() ? SerializationOption.ReflectionAsBackup : SerializationOption.CodeGenOnly;
+        }
         private static bool _optionAlreadySet;
         internal static SerializationOption Option
         {
diff --git a/src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/Program.cs b/src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/Program.cs
new file mode 100644
index 0000000000000..884dfa7ae893b
--- /dev/null
+++ b/src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/Program.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml;
+
+public static class Program
+{
+    [DllImport("__Internal")]
+    public static extern void mono_ios_set_summary (string value);
+
+    public static async Task<int> Main(string[] args)
+    {
+        mono_ios_set_summary($"Starting functional test");
+
+        var ds = new DataContractSerializer (typeof (IEnumerable<int>));
+        using (var xw = XmlWriter.Create (System.IO.Stream.Null))
+	        ds.WriteObject (xw, new int [] { 1, 2, 3 });
+
+        Console.WriteLine("Done!");
+        await Task.Delay(5000);
+
+        return 42;
+    }
+}
diff --git a/src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/iOS.Simulator.XmlFormatWriterGeneratorAot.Test.csproj b/src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/iOS.Simulator.XmlFormatWriterGeneratorAot.Test.csproj
new file mode 100644
index 0000000000000..f0a56aa7fdf05
--- /dev/null
+++ b/src/tests/FunctionalTests/iOS/Simulator/XmlFormatWriterGeneratorAOT/iOS.Simulator.XmlFormatWriterGeneratorAot.Test.csproj
@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk" TreatAsLocalProperty="MonoForceInterpreter">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <MonoForceInterpreter>false</MonoForceInterpreter>
+    <RunAOTCompilation>true</RunAOTCompilation>
+    <TestRuntime>true</TestRuntime>
+    <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetOS Condition="'$(TargetOS)' == ''">iOSSimulator</TargetOS>
+    <MainLibraryFileName>iOS.Simulator.XmlFormatWriterGeneratorAot.Test.dll</MainLibraryFileName>
+    <IncludesTestRunner>false</IncludesTestRunner>
+    <ExpectedExitCode>42</ExpectedExitCode>
+    <EnableAggressiveTrimming>true</EnableAggressiveTrimming>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+  </ItemGroup>
+</Project>

From d34d451434964b1be0a239d6fa726ea81ba65cca Mon Sep 17 00:00:00 2001
From: Maxim Lipnin <v-maxlip@microsoft.com>
Date: Mon, 12 Jul 2021 15:43:57 +0300
Subject: [PATCH 2/4] Use more appropriate method name

---
 .../System/Runtime/Serialization/DataContractSerializer.cs   | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
index 7ec3793d7bd18..3c7a76d8ce18f 100644
--- a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
+++ b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
@@ -34,9 +34,8 @@ public sealed class DataContractSerializer : XmlObjectSerializer
         private ISerializationSurrogateProvider? _serializationSurrogateProvider;
         private bool _serializeReadOnlyTypes;
 
-        private static SerializationOption _option = SetSerializationOption();
-
-        private static SerializationOption SetSerializationOption()
+        private static SerializationOption _option = GetDefaultSerializationOption();
+        private static SerializationOption GetDefaultSerializationOption()
         {
             if (OperatingSystem.IsIOS() || OperatingSystem.IsTvOS() || OperatingSystem.IsMacCatalyst())
             {

From 3756ea55216a0635bce915661760de5e3cd866bd Mon Sep 17 00:00:00 2001
From: Maxim Lipnin <v-maxlip@microsoft.com>
Date: Mon, 12 Jul 2021 22:52:47 +0300
Subject: [PATCH 3/4] Directly overwrite Option property to make it
 linker-friendly

---
 .../src/ILLink/ILLink.Substitutions.xml               |  5 +++++
 .../System.Private.DataContractSerialization.csproj   |  3 +++
 .../Runtime/Serialization/DataContractSerializer.cs   | 11 +----------
 3 files changed, 9 insertions(+), 10 deletions(-)
 create mode 100644 src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml

diff --git a/src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml b/src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml
new file mode 100644
index 0000000000000..6205f1177bed6
--- /dev/null
+++ b/src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml
@@ -0,0 +1,5 @@
+<linker>
+  <type fullname="System.Runtime.Serialization.DataContractSerializer" featurevalue="true" feature="System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported">
+    <method signature="System.Runtime.Serialization.DataContractSerializer.SerializationOption get_Option()" body="stub" value="1" />
+  </type>
+</linker>
\ No newline at end of file
diff --git a/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj b/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj
index 57474c6e2464b..28c4fa06c95c5 100644
--- a/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj
+++ b/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj
@@ -7,6 +7,9 @@
     <ILLinkTrimAssembly>false</ILLinkTrimAssembly>
     <Nullable>enable</Nullable>
   </PropertyGroup>
+  <ItemGroup>
+    <ILLinkSubstitutionsXmls Include="ILLink\ILLink.Substitutions.xml" />
+  </ItemGroup>
   <PropertyGroup>
     <RuntimeSerializationSources>System\Runtime\Serialization</RuntimeSerializationSources>
     <JsonSources>System\Runtime\Serialization\Json</JsonSources>
diff --git a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
index 3c7a76d8ce18f..71f4530f4f3d1 100644
--- a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
+++ b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
@@ -34,16 +34,7 @@ public sealed class DataContractSerializer : XmlObjectSerializer
         private ISerializationSurrogateProvider? _serializationSurrogateProvider;
         private bool _serializeReadOnlyTypes;
 
-        private static SerializationOption _option = GetDefaultSerializationOption();
-        private static SerializationOption GetDefaultSerializationOption()
-        {
-            if (OperatingSystem.IsIOS() || OperatingSystem.IsTvOS() || OperatingSystem.IsMacCatalyst())
-            {
-                return SerializationOption.ReflectionOnly;
-            }
-
-            return IsReflectionBackupAllowed() ? SerializationOption.ReflectionAsBackup : SerializationOption.CodeGenOnly;
-        }
+        private static SerializationOption _option = IsReflectionBackupAllowed() ? SerializationOption.ReflectionAsBackup : SerializationOption.CodeGenOnly;
         private static bool _optionAlreadySet;
         internal static SerializationOption Option
         {

From e9e0959b6e104f5bb202165b4e5ab2fcb64a50dd Mon Sep 17 00:00:00 2001
From: Maxim Lipnin <v-maxlip@microsoft.com>
Date: Tue, 13 Jul 2021 11:04:52 +0300
Subject: [PATCH 4/4] Change the Option property

---
 .../src/ILLink/ILLink.Substitutions.xml                      | 5 -----
 .../src/System.Private.DataContractSerialization.csproj      | 3 ---
 .../System/Runtime/Serialization/DataContractSerializer.cs   | 2 +-
 3 files changed, 1 insertion(+), 9 deletions(-)
 delete mode 100644 src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml

diff --git a/src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml b/src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml
deleted file mode 100644
index 6205f1177bed6..0000000000000
--- a/src/libraries/System.Private.DataContractSerialization/src/ILLink/ILLink.Substitutions.xml
+++ /dev/null
@@ -1,5 +0,0 @@
-<linker>
-  <type fullname="System.Runtime.Serialization.DataContractSerializer" featurevalue="true" feature="System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported">
-    <method signature="System.Runtime.Serialization.DataContractSerializer.SerializationOption get_Option()" body="stub" value="1" />
-  </type>
-</linker>
\ No newline at end of file
diff --git a/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj b/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj
index 28c4fa06c95c5..57474c6e2464b 100644
--- a/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj
+++ b/src/libraries/System.Private.DataContractSerialization/src/System.Private.DataContractSerialization.csproj
@@ -7,9 +7,6 @@
     <ILLinkTrimAssembly>false</ILLinkTrimAssembly>
     <Nullable>enable</Nullable>
   </PropertyGroup>
-  <ItemGroup>
-    <ILLinkSubstitutionsXmls Include="ILLink\ILLink.Substitutions.xml" />
-  </ItemGroup>
   <PropertyGroup>
     <RuntimeSerializationSources>System\Runtime\Serialization</RuntimeSerializationSources>
     <JsonSources>System\Runtime\Serialization\Json</JsonSources>
diff --git a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
index 71f4530f4f3d1..72229faaf8d3c 100644
--- a/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
+++ b/src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/DataContractSerializer.cs
@@ -38,7 +38,7 @@ public sealed class DataContractSerializer : XmlObjectSerializer
         private static bool _optionAlreadySet;
         internal static SerializationOption Option
         {
-            get { return _option; }
+            get { return RuntimeFeature.IsDynamicCodeSupported ? _option : SerializationOption.ReflectionOnly; }
             set
             {
                 if (_optionAlreadySet)