From 903926f8274a57f38f77316ee534febda354b45e Mon Sep 17 00:00:00 2001
From: Keegan Caruso <keegancaruso@microsoft.com>
Date: Wed, 16 Oct 2024 14:59:51 -0700
Subject: [PATCH 1/6] Don't use a GVM in Linq Select with NAOT by default

Adds a feature flag to allow Linq Select to not use
a GVM implementation.
---
 .../System.Linq/src/System.Linq.csproj        |  1 +
 .../src/System/Linq/IteratorOptions.cs        | 16 +++++++++++++
 .../src/System/Linq/OfType.SpeedOpt.cs        |  2 +-
 .../System.Linq/src/System/Linq/Select.cs     | 23 ++++++++++++++++++-
 .../build/Microsoft.NET.ILLink.targets        |  1 +
 5 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs

diff --git a/src/libraries/System.Linq/src/System.Linq.csproj b/src/libraries/System.Linq/src/System.Linq.csproj
index 79c10444f489b..32500dfa5ebd6 100644
--- a/src/libraries/System.Linq/src/System.Linq.csproj
+++ b/src/libraries/System.Linq/src/System.Linq.csproj
@@ -64,6 +64,7 @@
     <Compile Include="System\Linq\Index.cs" />
     <Compile Include="System\Linq\Intersect.cs" />
     <Compile Include="System\Linq\Iterator.cs" />
+    <Compile Include="System\Linq\IteratorOptions.cs" />
     <Compile Include="System\Linq\Join.cs" />
     <Compile Include="System\Linq\Last.cs" />
     <Compile Include="System\Linq\Lookup.cs" />
diff --git a/src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs b/src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs
new file mode 100644
index 0000000000000..226b84338337a
--- /dev/null
+++ b/src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Linq
+{
+    /// <summary>
+    /// Defines options for how iterators behave.
+    /// </summary>
+    internal static class IteratorOptions
+    {
+        [FeatureSwitchDefinition("System.Linq.ValueTypeTrimFriendlySelect")]
+        public static bool ValueTypeTrimFriendlySelect { get; } = AppContext.TryGetSwitch("System.Linq.ValueTypeTrimFriendlySelect", out bool isEnabled) ? isEnabled : true;
+    }
+}
diff --git a/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs b/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
index 73983cf87fbde..bbe3810251830 100644
--- a/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
+++ b/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
@@ -172,7 +172,7 @@ public override IEnumerable<TResult2> Select<TResult2>(Func<TResult, TResult2> s
                         new IEnumerableWhereSelectIterator<object, TResult2>(objectSource, isTResult, localSelector);
                 }
 
-                return base.Select(selector);
+                return SelectImplementation(selector, this);
             }
         }
     }
diff --git a/src/libraries/System.Linq/src/System/Linq/Select.cs b/src/libraries/System.Linq/src/System/Linq/Select.cs
index 37a41c450f873..e0f8f586f6cd8 100644
--- a/src/libraries/System.Linq/src/System/Linq/Select.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Select.cs
@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
 using static System.Linq.Utilities;
 
 namespace System.Linq
@@ -25,7 +26,7 @@ public static IEnumerable<TResult> Select<TSource, TResult>(
 
             if (source is Iterator<TSource> iterator)
             {
-                return iterator.Select(selector);
+                return SelectImplementation(selector, iterator);
             }
 
             if (source is IList<TSource> ilist)
@@ -51,6 +52,26 @@ public static IEnumerable<TResult> Select<TSource, TResult>(
             return new IEnumerableSelectIterator<TSource, TResult>(source, selector);
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static IEnumerable<TResult> SelectImplementation<TSource, TResult>(Func<TSource, TResult> selector, Iterator<TSource> iterator)
+        {
+            // In Native AOT, GVMs with Value types are not trim friendly.
+            // If the option is enabled, we don't call the GVM for value types. We don't do the
+            // same for reference types because reference types are trim friendly with GVMs
+            // and it is preferable to call the GVM as it allows the select implementation to be
+            // specialized.
+            if (IteratorOptions.ValueTypeTrimFriendlySelect && typeof(TResult).IsValueType)
+            {
+#if OPTIMIZE_FOR_SIZE
+                return new IEnumerableSelectIterator<TSource, TResult>(iterator, selector);
+#else
+                return new IteratorSelectIterator<TSource, TResult>(iterator, selector);
+#endif
+            }
+
+            return iterator.Select(selector);
+        }
+
         public static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, int, TResult> selector)
         {
             if (source is null)
diff --git a/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets b/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets
index 3fdf083a3beda..eff4d7bef6f30 100644
--- a/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets
+++ b/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets
@@ -38,6 +38,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     <EnableUnsafeBinaryFormatterSerialization Condition="'$(EnableUnsafeBinaryFormatterSerialization)' == ''">false</EnableUnsafeBinaryFormatterSerialization>
     <EnableUnsafeUTF7Encoding Condition="'$(EnableUnsafeUTF7Encoding)' == ''">false</EnableUnsafeUTF7Encoding>
     <BuiltInComInteropSupport Condition="'$(BuiltInComInteropSupport)' == ''">false</BuiltInComInteropSupport>
+    <ValueTypeTrimFriendlySelect Condition="'$(ValueTypeTrimFriendlySelect)' == ''">true</ValueTypeTrimFriendlySelect>
     <!-- GeneratedComInterface/ComImport interop requires built-in COM -->
     <EnableGeneratedComInterfaceComImportInterop Condition="'$(BuiltInComInteropSupport)' == 'false'">false</EnableGeneratedComInterfaceComImportInterop>
     <EnableGeneratedComInterfaceComImportInterop Condition="'$(EnableGeneratedComInterfaceComImportInterop)' == ''">false</EnableGeneratedComInterfaceComImportInterop>

From 0827a708b2da60ee7cb2244e2afa9490780abf58 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Strehovsk=C3=BD?=
 <MichalStrehovsky@users.noreply.github.com>
Date: Tue, 19 Nov 2024 23:07:03 -0800
Subject: [PATCH 2/6] Temporary change so we can run testing on this

---
 src/libraries/System.Linq/src/System/Linq/Select.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/System.Linq/src/System/Linq/Select.cs b/src/libraries/System.Linq/src/System/Linq/Select.cs
index e0f8f586f6cd8..07cd6736645da 100644
--- a/src/libraries/System.Linq/src/System/Linq/Select.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Select.cs
@@ -60,7 +60,7 @@ private static IEnumerable<TResult> SelectImplementation<TSource, TResult>(Func<
             // same for reference types because reference types are trim friendly with GVMs
             // and it is preferable to call the GVM as it allows the select implementation to be
             // specialized.
-            if (IteratorOptions.ValueTypeTrimFriendlySelect && typeof(TResult).IsValueType)
+            if (/*IteratorOptions.ValueTypeTrimFriendlySelect && */typeof(TResult).IsValueType)
             {
 #if OPTIMIZE_FOR_SIZE
                 return new IEnumerableSelectIterator<TSource, TResult>(iterator, selector);

From 616d23c85c408eb953524df99f41842ab3df47cc Mon Sep 17 00:00:00 2001
From: Keegan <keegancaruso@gmail.com>
Date: Tue, 26 Nov 2024 15:47:30 -0800
Subject: [PATCH 3/6] Update
 src/libraries/System.Linq/src/System/Linq/Select.cs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Michal Strehovský <MichalStrehovsky@users.noreply.github.com>
---
 src/libraries/System.Linq/src/System/Linq/Select.cs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/libraries/System.Linq/src/System/Linq/Select.cs b/src/libraries/System.Linq/src/System/Linq/Select.cs
index 07cd6736645da..fac0978314cb6 100644
--- a/src/libraries/System.Linq/src/System/Linq/Select.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Select.cs
@@ -55,11 +55,11 @@ public static IEnumerable<TResult> Select<TSource, TResult>(
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static IEnumerable<TResult> SelectImplementation<TSource, TResult>(Func<TSource, TResult> selector, Iterator<TSource> iterator)
         {
-            // In Native AOT, GVMs with Value types are not trim friendly.
-            // If the option is enabled, we don't call the GVM for value types. We don't do the
-            // same for reference types because reference types are trim friendly with GVMs
-            // and it is preferable to call the GVM as it allows the select implementation to be
-            // specialized.
+            // With native AOT, calling into the `Select` generic virtual method results in NxM
+            // expansion of native code. If the option is enabled, we don't call the generic virtual
+            // for value types. We don't do the same for reference types because reference type
+            // expansion can happen lazily at runtime and the AOT compiler does postpone it (we
+            // don't need more code, just more data structures describing the new types).
             if (/*IteratorOptions.ValueTypeTrimFriendlySelect && */typeof(TResult).IsValueType)
             {
 #if OPTIMIZE_FOR_SIZE

From 67674d5a4015b5b5ef0224d1b7dbe7fa7ace6daa Mon Sep 17 00:00:00 2001
From: Keegan Caruso <keegancaruso@microsoft.com>
Date: Tue, 26 Nov 2024 18:42:23 -0800
Subject: [PATCH 4/6] PR Feedback

- Don't set feature flag by default for trimming
- Move option to Enumerable
- Fix error in OfType.SpeedOpt
---
 src/libraries/System.Linq/src/System.Linq.csproj |  1 -
 .../System.Linq/src/System/Linq/Enumerable.cs    |  4 ++++
 .../src/System/Linq/IteratorOptions.cs           | 16 ----------------
 .../src/System/Linq/OfType.SpeedOpt.cs           |  2 +-
 .../System.Linq/src/System/Linq/Select.cs        |  2 +-
 .../build/Microsoft.NET.ILLink.targets           |  1 -
 6 files changed, 6 insertions(+), 20 deletions(-)
 delete mode 100644 src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs

diff --git a/src/libraries/System.Linq/src/System.Linq.csproj b/src/libraries/System.Linq/src/System.Linq.csproj
index 32500dfa5ebd6..79c10444f489b 100644
--- a/src/libraries/System.Linq/src/System.Linq.csproj
+++ b/src/libraries/System.Linq/src/System.Linq.csproj
@@ -64,7 +64,6 @@
     <Compile Include="System\Linq\Index.cs" />
     <Compile Include="System\Linq\Intersect.cs" />
     <Compile Include="System\Linq\Iterator.cs" />
-    <Compile Include="System\Linq\IteratorOptions.cs" />
     <Compile Include="System\Linq\Join.cs" />
     <Compile Include="System\Linq\Last.cs" />
     <Compile Include="System\Linq\Lookup.cs" />
diff --git a/src/libraries/System.Linq/src/System/Linq/Enumerable.cs b/src/libraries/System.Linq/src/System/Linq/Enumerable.cs
index fbdf9a12a28b6..cc508f8446017 100644
--- a/src/libraries/System.Linq/src/System/Linq/Enumerable.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Enumerable.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
@@ -63,5 +64,8 @@ internal static bool TryGetSpan<TSource>(this IEnumerable<TSource> source, out R
 
             return result;
         }
+
+        [FeatureSwitchDefinition("System.Linq.Enumerable.ValueTypeTrimFriendlySelect")]
+        internal static bool ValueTypeTrimFriendlySelect { get; } = AppContext.TryGetSwitch("System.Linq.Enumerable.ValueTypeTrimFriendlySelect", out bool isEnabled) ? isEnabled : false;
     }
 }
diff --git a/src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs b/src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs
deleted file mode 100644
index 226b84338337a..0000000000000
--- a/src/libraries/System.Linq/src/System/Linq/IteratorOptions.cs
+++ /dev/null
@@ -1,16 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-using System.Diagnostics.CodeAnalysis;
-
-namespace System.Linq
-{
-    /// <summary>
-    /// Defines options for how iterators behave.
-    /// </summary>
-    internal static class IteratorOptions
-    {
-        [FeatureSwitchDefinition("System.Linq.ValueTypeTrimFriendlySelect")]
-        public static bool ValueTypeTrimFriendlySelect { get; } = AppContext.TryGetSwitch("System.Linq.ValueTypeTrimFriendlySelect", out bool isEnabled) ? isEnabled : true;
-    }
-}
diff --git a/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs b/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
index bbe3810251830..f059542b72bd2 100644
--- a/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
+++ b/src/libraries/System.Linq/src/System/Linq/OfType.SpeedOpt.cs
@@ -172,7 +172,7 @@ public override IEnumerable<TResult2> Select<TResult2>(Func<TResult, TResult2> s
                         new IEnumerableWhereSelectIterator<object, TResult2>(objectSource, isTResult, localSelector);
                 }
 
-                return SelectImplementation(selector, this);
+                return new IteratorSelectIterator<TResult, TResult2>(this, selector);
             }
         }
     }
diff --git a/src/libraries/System.Linq/src/System/Linq/Select.cs b/src/libraries/System.Linq/src/System/Linq/Select.cs
index fac0978314cb6..79700032a69d7 100644
--- a/src/libraries/System.Linq/src/System/Linq/Select.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Select.cs
@@ -60,7 +60,7 @@ private static IEnumerable<TResult> SelectImplementation<TSource, TResult>(Func<
             // for value types. We don't do the same for reference types because reference type
             // expansion can happen lazily at runtime and the AOT compiler does postpone it (we
             // don't need more code, just more data structures describing the new types).
-            if (/*IteratorOptions.ValueTypeTrimFriendlySelect && */typeof(TResult).IsValueType)
+            if (/*ValueTypeTrimFriendlySelect &&*/ typeof(TResult).IsValueType)
             {
 #if OPTIMIZE_FOR_SIZE
                 return new IEnumerableSelectIterator<TSource, TResult>(iterator, selector);
diff --git a/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets b/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets
index eff4d7bef6f30..3fdf083a3beda 100644
--- a/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets
+++ b/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets
@@ -38,7 +38,6 @@ Copyright (c) .NET Foundation. All rights reserved.
     <EnableUnsafeBinaryFormatterSerialization Condition="'$(EnableUnsafeBinaryFormatterSerialization)' == ''">false</EnableUnsafeBinaryFormatterSerialization>
     <EnableUnsafeUTF7Encoding Condition="'$(EnableUnsafeUTF7Encoding)' == ''">false</EnableUnsafeUTF7Encoding>
     <BuiltInComInteropSupport Condition="'$(BuiltInComInteropSupport)' == ''">false</BuiltInComInteropSupport>
-    <ValueTypeTrimFriendlySelect Condition="'$(ValueTypeTrimFriendlySelect)' == ''">true</ValueTypeTrimFriendlySelect>
     <!-- GeneratedComInterface/ComImport interop requires built-in COM -->
     <EnableGeneratedComInterfaceComImportInterop Condition="'$(BuiltInComInteropSupport)' == 'false'">false</EnableGeneratedComInterfaceComImportInterop>
     <EnableGeneratedComInterfaceComImportInterop Condition="'$(EnableGeneratedComInterfaceComImportInterop)' == ''">false</EnableGeneratedComInterfaceComImportInterop>

From d96f35a29985925af0ee78914d9aa7d89085612b Mon Sep 17 00:00:00 2001
From: Keegan Caruso <keegancaruso@microsoft.com>
Date: Tue, 26 Nov 2024 18:43:09 -0800
Subject: [PATCH 5/6] temporary: enable option by default for testing

---
 src/libraries/System.Linq/src/System/Linq/Enumerable.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/System.Linq/src/System/Linq/Enumerable.cs b/src/libraries/System.Linq/src/System/Linq/Enumerable.cs
index cc508f8446017..6b591259337a5 100644
--- a/src/libraries/System.Linq/src/System/Linq/Enumerable.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Enumerable.cs
@@ -66,6 +66,6 @@ internal static bool TryGetSpan<TSource>(this IEnumerable<TSource> source, out R
         }
 
         [FeatureSwitchDefinition("System.Linq.Enumerable.ValueTypeTrimFriendlySelect")]
-        internal static bool ValueTypeTrimFriendlySelect { get; } = AppContext.TryGetSwitch("System.Linq.Enumerable.ValueTypeTrimFriendlySelect", out bool isEnabled) ? isEnabled : false;
+        internal static bool ValueTypeTrimFriendlySelect { get; } = AppContext.TryGetSwitch("System.Linq.Enumerable.ValueTypeTrimFriendlySelect", out bool isEnabled) ? isEnabled : true;
     }
 }

From 41d7467ed7d8418f6498323fd69d42ffa88eb76c Mon Sep 17 00:00:00 2001
From: Keegan Caruso <keegancaruso@microsoft.com>
Date: Wed, 27 Nov 2024 11:06:06 -0800
Subject: [PATCH 6/6] Use remote executor for tests using appcontext

---
 .../System.Linq/src/System/Linq/Select.cs     |  2 +-
 .../System.Linq/tests/SkipWhileTests.cs       | 32 +++++++++++++++----
 .../tests/System.Linq.Tests.csproj            |  1 +
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/libraries/System.Linq/src/System/Linq/Select.cs b/src/libraries/System.Linq/src/System/Linq/Select.cs
index 79700032a69d7..db9adc9874030 100644
--- a/src/libraries/System.Linq/src/System/Linq/Select.cs
+++ b/src/libraries/System.Linq/src/System/Linq/Select.cs
@@ -60,7 +60,7 @@ private static IEnumerable<TResult> SelectImplementation<TSource, TResult>(Func<
             // for value types. We don't do the same for reference types because reference type
             // expansion can happen lazily at runtime and the AOT compiler does postpone it (we
             // don't need more code, just more data structures describing the new types).
-            if (/*ValueTypeTrimFriendlySelect &&*/ typeof(TResult).IsValueType)
+            if (ValueTypeTrimFriendlySelect && typeof(TResult).IsValueType)
             {
 #if OPTIMIZE_FOR_SIZE
                 return new IEnumerableSelectIterator<TSource, TResult>(iterator, selector);
diff --git a/src/libraries/System.Linq/tests/SkipWhileTests.cs b/src/libraries/System.Linq/tests/SkipWhileTests.cs
index a13a686cef3f3..5884d9c7ce3c1 100644
--- a/src/libraries/System.Linq/tests/SkipWhileTests.cs
+++ b/src/libraries/System.Linq/tests/SkipWhileTests.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
+using Microsoft.DotNet.RemoteExecutor;
 using Xunit;
 
 namespace System.Linq.Tests
@@ -62,14 +63,33 @@ public void RunOnce()
             Assert.Equal(Enumerable.Range(10, 10), Enumerable.Range(0, 20).RunOnce().SkipWhile((i, idx) => idx < 10));
         }
 
-        [Fact]
-        public void SkipErrorWhenSourceErrors()
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public static void SkipErrorWhenSourceErrors_TrimFriendlySelectTrue()
         {
-            var source = NumberRangeGuaranteedNotCollectionType(-2, 5).Select(i => (decimal)i).Select(m => 1 / m).Skip(4);
-            using(var en = source.GetEnumerator())
+            RemoteExecutor.Invoke(() =>
             {
-                Assert.Throws<DivideByZeroException>(() => en.MoveNext());
-            }
+                AppContext.SetSwitch("System.Linq.Enumerable.ValueTypeTrimFriendlySelect", true);
+
+                var source = NumberRangeGuaranteedNotCollectionType(-2, 5).Select(i => (decimal)i).Select(m => 1 / m).Skip(4);
+                var valuesFromEnumerable = source.ToList();
+                List<decimal> expectedValues = [(decimal)1/2];
+                Assert.Equal(expectedValues, valuesFromEnumerable);
+            }).Dispose();
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void SkipErrorWhenSourceErrors_TrimFriendlySelectFalse()
+        {
+            RemoteExecutor.Invoke(() =>
+            {
+                AppContext.SetSwitch("System.Linq.Enumerable.ValueTypeTrimFriendlySelect", false);
+
+                var source = NumberRangeGuaranteedNotCollectionType(-2, 5).Select(i => (decimal)i).Select(m => 1 / m).Skip(4);
+                using (var en = source.GetEnumerator())
+                {
+                    Assert.Throws<DivideByZeroException>(() => en.MoveNext());
+                }
+            }).Dispose();
         }
 
         [Fact]
diff --git a/src/libraries/System.Linq/tests/System.Linq.Tests.csproj b/src/libraries/System.Linq/tests/System.Linq.Tests.csproj
index 1e4692999a174..ac0ef5e696463 100644
--- a/src/libraries/System.Linq/tests/System.Linq.Tests.csproj
+++ b/src/libraries/System.Linq/tests/System.Linq.Tests.csproj
@@ -1,5 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
+    <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
     <DebuggerSupport Condition="'$(DebuggerSupport)' == '' and '$(TargetOS)' == 'browser'">true</DebuggerSupport>
   </PropertyGroup>