Fix leak caused by not disposing the scoped parent service provider (#74261)

Author: tarekgh

src/libraries/Microsoft.Extensions.DependencyInjection/src/ServiceLookup/ServiceProviderEngineScope.cs

@@ -187,12 +187,20 @@ static async ValueTask Await(int i, ValueTask vt, List<object> toDispose)
                 // No further changes to _state.Disposables, are allowed.
                 _disposed = true;
 
-                // ResolvedServices is never cleared for singletons because there might be a compilation running in background
-                // trying to get a cached singleton service. If it doesn't find it
-                // it will try to create a new one which will result in an ObjectDisposedException.
+            }
 
-                return _disposables;
+            if (IsRootScope && !RootProvider.IsDisposed())
+            {
+                // If this ServiceProviderEngineScope instance is a root scope, disposing this instance will need to dispose the RootProvider too.
+                // Otherwise the RootProvider will never get disposed and will leak.
+                // Note, if the RootProvider get disposed first, it will automatically dispose all attached ServiceProviderEngineScope objects.
+                RootProvider.Dispose();
             }
+
+            // ResolvedServices is never cleared for singletons because there might be a compilation running in background
+            // trying to get a cached singleton service. If it doesn't find it
+            // it will try to create a new one which will result in an ObjectDisposedException.
+            return _disposables;
         }
     }
 }

src/libraries/Microsoft.Extensions.DependencyInjection/src/ServiceProvider.cs

@@ -89,6 +89,8 @@ internal ServiceProvider(ICollection<ServiceDescriptor> serviceDescriptors, Serv
         /// <returns>The service that was produced.</returns>
         public object? GetService(Type serviceType) => GetService(serviceType, Root);
 
+        internal bool IsDisposed() => _disposed;
+
         /// <inheritdoc />
         public void Dispose()
         {

src/libraries/Microsoft.Extensions.DependencyInjection/tests/DI.Tests/ServiceProviderEngineScopeTests.cs

@@ -1,6 +1,7 @@
 // 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 Microsoft.Extensions.DependencyInjection.Specification.Fakes;
 using Xunit;
 
@@ -17,5 +18,16 @@ public void DoubleDisposeWorks()
             serviceProviderEngineScope.Dispose();
             serviceProviderEngineScope.Dispose();
         }
+
+        [Fact]
+        public void RootEngineScopeDisposeTest()
+        {
+            var services = new ServiceCollection();
+            ServiceProvider sp = services.BuildServiceProvider();
+            var s = sp.GetRequiredService<IServiceProvider>();
+            ((IDisposable)s).Dispose();
+
+            Assert.Throws<ObjectDisposedException>(() => sp.GetRequiredService<IServiceProvider>());
+        }
     }
 }