Extract AuthenticationHelper class to a separate file for tvOS;

src/libraries/System.Net.Http/src/System.Net.Http.csproj

@@ -142,7 +142,7 @@
     <Compile Include="System\Net\Http\Headers\KnownHeader.Http2And3.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\AuthenticationHelper.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\AuthenticationHelper.Digest.cs" />
-    <Compile Include="System\Net\Http\SocketsHttpHandler\AuthenticationHelper.NtAuth.cs" />
+    <Compile Condition="'$(TargetstvOS)' != 'true'" Include="System\Net\Http\SocketsHttpHandler\AuthenticationHelper.NtAuth.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\ChunkedEncodingReadStream.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\ChunkedEncodingWriteStream.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\ConnectHelper.cs" />
@@ -348,6 +348,7 @@
              Link="Common\System\Net\Security\NegotiateStreamPal.Unix.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetstvOS)' == 'true'">
+    <Compile Include="System\Net\Http\SocketsHttpHandler\AuthenticationHelper.NtAuth.tvOS.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\GssSafeHandles.PlatformNotSupported.cs"
              Link="Common\Microsoft\Win32\SafeHandles\GssSafeHandles.PlatformNotSupported.cs" />
     <Compile Include="$(CommonPath)System\Net\Security\NegotiateStreamPal.PlatformNotSupported.cs"

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/AuthenticationHelper.NtAuth.cs

@@ -5,14 +5,12 @@
 using System.Diagnostics;
 using System.Net;
 using System.Net.Http.Headers;
-using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Security.Authentication.ExtendedProtection;
 
 namespace System.Net.Http
 {
-    [UnsupportedOSPlatform("tvos")]
     internal static partial class AuthenticationHelper
     {
         private static Task<HttpResponseMessage> InnerSendAsync(HttpRequestMessage request, bool async, bool isProxyAuth, HttpConnectionPool pool, HttpConnection connection, CancellationToken cancellationToken)

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/AuthenticationHelper.NtAuth.tvOS.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.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Net.Http
+{
+    internal static partial class AuthenticationHelper
+    {
+        private static Task<HttpResponseMessage> InnerSendAsync(HttpRequestMessage request, Uri authUri, bool async, ICredentials credentials, bool isProxyAuth, HttpConnection connection, HttpConnectionPool connectionPool, CancellationToken cancellationToken)
+        {
+            return isProxyAuth ?
+                SendWithProxyAuthAsync(request, authUri, async, credentials, true, connectionPool, cancellationToken).AsTask() :
+                SendWithRequestAuthAsync(request, async, credentials, true, connectionPool, cancellationToken).AsTask();
+        }
+
+        public static Task<HttpResponseMessage> SendWithNtProxyAuthAsync(HttpRequestMessage request, Uri proxyUri, bool async, ICredentials proxyCredentials, HttpConnection connection, HttpConnectionPool connectionPool, CancellationToken cancellationToken)
+        {
+            return InnerSendAsync(request, proxyUri, async, proxyCredentials, isProxyAuth: true, connection, connectionPool, cancellationToken);
+        }
+
+        public static Task<HttpResponseMessage> SendWithNtConnectionAuthAsync(HttpRequestMessage request, bool async, ICredentials credentials, HttpConnection connection, HttpConnectionPool connectionPool, CancellationToken cancellationToken)
+        {
+            Debug.Assert(request.RequestUri != null);
+            return InnerSendAsync(request, request.RequestUri, async, credentials, isProxyAuth: false, connection, connectionPool, cancellationToken);
+        }
+    }
+}

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpAuthenticatedConnectionHandler.cs

@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -16,7 +15,6 @@ public HttpAuthenticatedConnectionHandler(HttpConnectionPoolManager poolManager)
             _poolManager = poolManager;
         }
 
-        [UnsupportedOSPlatform("tvos")]
         internal override ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             return _poolManager.SendAsync(request, async, doRequestAuth: true, cancellationToken);

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnection.cs

@@ -11,7 +11,6 @@
 using System.Net.Security;
 using System.Net.Sockets;
 using System.Runtime.CompilerServices;
-using System.Runtime.Versioning;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -377,7 +376,6 @@ private Task WriteHexInt32Async(int value, bool async)
             return WriteAsciiStringAsync(value.ToString("X", CultureInfo.InvariantCulture), async);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public async Task<HttpResponseMessage> SendAsyncCore(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             TaskCompletionSource<bool>? allowExpect100ToContinue = null;
@@ -804,7 +802,6 @@ public async Task<HttpResponseMessage> SendAsyncCore(HttpRequestMessage request,
             }
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public sealed override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken) =>
             SendAsyncCore(request, async, cancellationToken);
 

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionHandler.cs

@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -16,7 +15,6 @@ public HttpConnectionHandler(HttpConnectionPoolManager poolManager)
             _poolManager = poolManager;
         }
 
-        [UnsupportedOSPlatform("tvos")]
         internal override ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             return _poolManager.SendAsync(request, async, doRequestAuth: false, cancellationToken);

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs

@@ -471,7 +471,6 @@ private static HttpRequestException GetVersionException(HttpRequestMessage reque
         }
 
         // Returns null if HTTP2 cannot be used
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<Http2Connection?> GetHttp2ConnectionAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             Debug.Assert(_kind == HttpConnectionKind.Https || _kind == HttpConnectionKind.SslProxyTunnel || _kind == HttpConnectionKind.Http || _kind == HttpConnectionKind.SocksTunnel || _kind == HttpConnectionKind.SslSocksTunnel);
@@ -813,7 +812,6 @@ private async ValueTask<Http3Connection> GetHttp3ConnectionAsync(HttpRequestMess
         }
 
         // Returns null if HTTP2 cannot be used.
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<HttpResponseMessage?> TrySendUsingHttp2Async(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             // Send using HTTP/2 if we can.
@@ -834,7 +832,6 @@ private async ValueTask<Http3Connection> GetHttp3ConnectionAsync(HttpRequestMess
             return null;
         }
 
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<HttpResponseMessage> SendUsingHttp11Async(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             HttpConnection? connection = await GetOrReserveHttp11ConnectionAsync(async, cancellationToken).ConfigureAwait(false);
@@ -865,7 +862,6 @@ private async ValueTask<HttpResponseMessage> SendUsingHttp11Async(HttpRequestMes
             }
         }
 
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<HttpResponseMessage> DetermineVersionAndSendAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             HttpResponseMessage? response;
@@ -900,7 +896,6 @@ private async ValueTask<HttpResponseMessage> DetermineVersionAndSendAsync(HttpRe
             return await SendUsingHttp11Async(request, async, doRequestAuth, cancellationToken).ConfigureAwait(false);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<HttpResponseMessage> SendAndProcessAltSvcAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             HttpResponseMessage response = await DetermineVersionAndSendAsync(request, async, doRequestAuth, cancellationToken).ConfigureAwait(false);
@@ -914,7 +909,6 @@ private async ValueTask<HttpResponseMessage> SendAndProcessAltSvcAsync(HttpReque
             return response;
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public async ValueTask<HttpResponseMessage> SendWithRetryAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             int retryCount = 0;
@@ -1202,7 +1196,6 @@ public void OnNetworkChanged()
             }
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public Task<HttpResponseMessage> SendWithNtConnectionAuthAsync(HttpConnection connection, HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             if (doRequestAuth && Settings._credentials != null)
@@ -1215,7 +1208,6 @@ public Task<HttpResponseMessage> SendWithNtConnectionAuthAsync(HttpConnection co
 
         private bool DoProxyAuth => (_kind == HttpConnectionKind.Proxy || _kind == HttpConnectionKind.ProxyConnect);
 
-        [UnsupportedOSPlatform("tvos")]
         public Task<HttpResponseMessage> SendWithNtProxyAuthAsync(HttpConnection connection, HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             if (DoProxyAuth && ProxyCredentials is not null)
@@ -1226,7 +1218,6 @@ public Task<HttpResponseMessage> SendWithNtProxyAuthAsync(HttpConnection connect
             return connection.SendAsync(request, async, cancellationToken);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public ValueTask<HttpResponseMessage> SendWithProxyAuthAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             if (DoProxyAuth && ProxyCredentials is not null)
@@ -1237,7 +1228,6 @@ public ValueTask<HttpResponseMessage> SendWithProxyAuthAsync(HttpRequestMessage
             return SendWithRetryAsync(request, async, doRequestAuth, cancellationToken);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             if (doRequestAuth && Settings._credentials != null)
@@ -1248,7 +1238,6 @@ public ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool
             return SendWithProxyAuthAsync(request, async, doRequestAuth, cancellationToken);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<(Socket?, Stream, TransportContext?)> ConnectAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             // If a non-infinite connect timeout has been set, create and use a new CancellationToken that will be canceled
@@ -1369,7 +1358,6 @@ public ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool
             }
         }
 
-        [UnsupportedOSPlatform("tvos")]
         internal async ValueTask<HttpConnection> CreateHttp11ConnectionAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)
         {
             (Socket? socket, Stream? stream, TransportContext? transportContext) =
@@ -1464,7 +1452,6 @@ private async ValueTask<Http2Connection> ConstructHttp2ConnectionAsync(Stream st
             return http2Connection;
         }
 
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<Stream> EstablishProxyTunnelAsync(bool async, HttpRequestHeaders? headers, CancellationToken cancellationToken)
         {
             Debug.Assert(_originAuthority != null);

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPoolManager.cs

@@ -6,7 +6,6 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.ExceptionServices;
-using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Net.NetworkInformation;
@@ -327,7 +326,6 @@ private HttpConnectionKey GetConnectionKey(HttpRequestMessage request, Uri? prox
             }
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public ValueTask<HttpResponseMessage> SendAsyncCore(HttpRequestMessage request, Uri? proxyUri, bool async, bool doRequestAuth, bool isProxyConnect, CancellationToken cancellationToken)
         {
             HttpConnectionKey key = GetConnectionKey(request, proxyUri, isProxyConnect);
@@ -367,13 +365,11 @@ public ValueTask<HttpResponseMessage> SendAsyncCore(HttpRequestMessage request,
             return pool.SendAsync(request, async, doRequestAuth, cancellationToken);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public ValueTask<HttpResponseMessage> SendProxyConnectAsync(HttpRequestMessage request, Uri proxyUri, bool async, CancellationToken cancellationToken)
         {
             return SendAsyncCore(request, proxyUri, async, doRequestAuth: false, isProxyConnect: true, cancellationToken);
         }
 
-        [UnsupportedOSPlatform("tvos")]
         public ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, bool doRequestAuth, CancellationToken cancellationToken)
         {
             if (_proxy == null)
@@ -427,7 +423,6 @@ public ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool
         /// <param name="multiProxy">The set of proxies to use.</param>
         /// <param name="firstProxy">The first proxy try.</param>
         /// <param name="cancellationToken">The cancellation token to use for the operation.</param>
-        [UnsupportedOSPlatform("tvos")]
         private async ValueTask<HttpResponseMessage> SendAsyncMultiProxy(HttpRequestMessage request, bool async, bool doRequestAuth, MultiProxy multiProxy, Uri? firstProxy, CancellationToken cancellationToken)
         {
             HttpRequestException rethrowException;