From 721cf1fd04f906d3d4c5c2d561c594709c5744a8 Mon Sep 17 00:00:00 2001
From: martincostello <martin@martincostello.com>
Date: Sun, 17 Oct 2021 15:11:34 +0100
Subject: [PATCH 1/2] Fix IHost being disposed of twice

Fix the IHost wrapped by DeferredHost being disposed of twice if the
IHost implementation implements IAsyncDisposable.
---
 src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs b/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs
index ea58bf4faade..14194b0a1070 100644
--- a/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs
+++ b/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs
@@ -141,7 +141,10 @@ public async ValueTask DisposeAsync()
                     await disposable.DisposeAsync().ConfigureAwait(false);
                     return;
                 }
-                Dispose();
+                else
+                {
+                    _host.Dispose();
+                }
             }
 
             public async Task StartAsync(CancellationToken cancellationToken = default)

From 73018234aadcf0a662375f29e6fb6613a511124d Mon Sep 17 00:00:00 2001
From: martincostello <martin@martincostello.com>
Date: Sun, 17 Oct 2021 17:15:15 +0100
Subject: [PATCH 2/2] Do not dispose the host twice

Do not dispose the IHost multiple times if disposed more than once.
---
 src/DefaultBuilder/src/WebApplication.cs      | 20 ++++++++++++++++--
 .../Mvc.Testing/src/DeferredHostBuilder.cs    | 21 +++++++++++--------
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/src/DefaultBuilder/src/WebApplication.cs b/src/DefaultBuilder/src/WebApplication.cs
index 9d0a837c8300..e9dcd85efc20 100644
--- a/src/DefaultBuilder/src/WebApplication.cs
+++ b/src/DefaultBuilder/src/WebApplication.cs
@@ -24,6 +24,8 @@ public sealed class WebApplication : IHost, IApplicationBuilder, IEndpointRouteB
         private readonly IHost _host;
         private readonly List<EndpointDataSource> _dataSources = new();
 
+        private bool _disposed;
+
         internal WebApplication(IHost host)
         {
             _host = host;
@@ -162,12 +164,26 @@ public void Run(string? url = null)
         /// <summary>
         /// Disposes the application.
         /// </summary>
-        void IDisposable.Dispose() => _host.Dispose();
+        void IDisposable.Dispose()
+        {
+            if (!_disposed)
+            {
+                _host.Dispose();
+                _disposed = true;
+            }
+        }
 
         /// <summary>
         /// Disposes the application.
         /// </summary>
-        public ValueTask DisposeAsync() => ((IAsyncDisposable)_host).DisposeAsync();
+        public async ValueTask DisposeAsync()
+        {
+            if (!_disposed)
+            {
+                await ((IAsyncDisposable)_host).DisposeAsync();
+                _disposed = true;
+            }
+        }
 
         internal RequestDelegate BuildRequestDelegate() => ApplicationBuilder.Build();
         RequestDelegate IApplicationBuilder.Build() => BuildRequestDelegate();
diff --git a/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs b/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs
index 14194b0a1070..ddb3da2dd95a 100644
--- a/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs
+++ b/src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs
@@ -1,10 +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;
-using System.Collections.Generic;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -124,6 +120,8 @@ private class DeferredHost : IHost, IAsyncDisposable
             private readonly IHost _host;
             private readonly TaskCompletionSource _hostStartedTcs;
 
+            private bool _disposed;
+
             public DeferredHost(IHost host, TaskCompletionSource hostStartedTcs)
             {
                 _host = host;
@@ -132,19 +130,24 @@ public DeferredHost(IHost host, TaskCompletionSource hostStartedTcs)
 
             public IServiceProvider Services => _host.Services;
 
-            public void Dispose() => _host.Dispose();
+            public void Dispose()
+            {
+                if (!_disposed)
+                {
+                    _host.Dispose();
+                    _disposed = true;
+                }
+            }
 
             public async ValueTask DisposeAsync()
             {
                 if (_host is IAsyncDisposable disposable)
                 {
                     await disposable.DisposeAsync().ConfigureAwait(false);
+                    _disposed = true;
                     return;
                 }
-                else
-                {
-                    _host.Dispose();
-                }
+                Dispose();
             }
 
             public async Task StartAsync(CancellationToken cancellationToken = default)