From b08577342dc39bc8e6051a66311bfc40f623fccc Mon Sep 17 00:00:00 2001
From: Mikael Mengistu <mikaelm12@users.noreply.github.com>
Date: Thu, 6 Jun 2019 08:33:32 -0700
Subject: [PATCH] Lazy-init formatter resolvers in
 MessagePackHubProtocolOptions (#10929)

---
 ...lR.Protocols.MessagePack.netstandard2.0.cs |  2 +-
 .../src/MessagePackHubProtocolOptions.cs      | 21 ++++++++++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/SignalR/common/Protocols.MessagePack/ref/Microsoft.AspNetCore.SignalR.Protocols.MessagePack.netstandard2.0.cs b/src/SignalR/common/Protocols.MessagePack/ref/Microsoft.AspNetCore.SignalR.Protocols.MessagePack.netstandard2.0.cs
index ec222f2318..70f7ce9d02 100644
--- a/src/SignalR/common/Protocols.MessagePack/ref/Microsoft.AspNetCore.SignalR.Protocols.MessagePack.netstandard2.0.cs
+++ b/src/SignalR/common/Protocols.MessagePack/ref/Microsoft.AspNetCore.SignalR.Protocols.MessagePack.netstandard2.0.cs
@@ -6,7 +6,7 @@ namespace Microsoft.AspNetCore.SignalR
     public partial class MessagePackHubProtocolOptions
     {
         public MessagePackHubProtocolOptions() { }
-        public System.Collections.Generic.IList<MessagePack.IFormatterResolver> FormatterResolvers { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute]set { } }
+        public System.Collections.Generic.IList<MessagePack.IFormatterResolver> FormatterResolvers { get { throw null; } set { } }
     }
 }
 namespace Microsoft.AspNetCore.SignalR.Protocol
diff --git a/src/SignalR/common/Protocols.MessagePack/src/MessagePackHubProtocolOptions.cs b/src/SignalR/common/Protocols.MessagePack/src/MessagePackHubProtocolOptions.cs
index 95ddfe6a9b..85025b6444 100644
--- a/src/SignalR/common/Protocols.MessagePack/src/MessagePackHubProtocolOptions.cs
+++ b/src/SignalR/common/Protocols.MessagePack/src/MessagePackHubProtocolOptions.cs
@@ -9,6 +9,25 @@ namespace Microsoft.AspNetCore.SignalR
 {
     public class MessagePackHubProtocolOptions
     {
-        public IList<IFormatterResolver> FormatterResolvers { get; set; } = MessagePackHubProtocol.CreateDefaultFormatterResolvers();
+        private IList<IFormatterResolver> _formatterResolvers;
+
+        public IList<IFormatterResolver> FormatterResolvers
+        {
+            get
+            {
+                if (_formatterResolvers == null)
+                {
+                    // The default set of resolvers trigger a static constructor that throws on AOT environments.
+                    // This gives users the chance to use an AOT friendly formatter.
+                    _formatterResolvers = MessagePackHubProtocol.CreateDefaultFormatterResolvers();
+                }
+
+                return _formatterResolvers;
+            }
+            set
+            {
+                _formatterResolvers = value;
+            }
+        }
     }
 }