Add support for Func<TArgs, Task> handlers for Core Autofac Events

src/Autofac/Autofac.csproj

@@ -44,10 +44,10 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.0.0">
+    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.0-beta1.final">
       <PrivateAssets>All</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="3.0.0">
+    <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="3.3.0-beta2.final">
       <PrivateAssets>All</PrivateAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" Condition="Exists('$(MSBuildThisFileDirectory)../../.git')">

src/Autofac/Builder/IRegistrationBuilder.cs

@@ -26,6 +26,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Threading.Tasks;
 using Autofac.Core;
 using Autofac.Core.Resolving.Pipeline;
 
@@ -257,20 +258,42 @@ IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> Keyed<TService>
         /// <returns>A registration builder allowing further configuration of the component.</returns>
         IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnPreparing(Action<PreparingEventArgs> handler);
 
+        /// <summary>
+        /// Add an async handler for the Preparing event. This event allows manipulating of the parameters
+        /// that will be provided to the component.
+        /// </summary>
+        /// <param name="handler">An event handler; the resolve process will not continue until the returned task completes.</param>
+        /// <returns>A registration builder allowing further configuration of the component.</returns>
+        IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnPreparing(Func<PreparingEventArgs, ValueTask> handler);
+
         /// <summary>
         /// Add a handler for the Activating event.
         /// </summary>
         /// <param name="handler">The event handler.</param>
         /// <returns>A registration builder allowing further configuration of the component.</returns>
         IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActivating(Action<IActivatingEventArgs<TLimit>> handler);
 
+        /// <summary>
+        /// Add an async handler for the Activating event.
+        /// </summary>
+        /// <param name="handler">An event handler; the resolve process will not continue until the returned task completes.</param>
+        /// <returns>A registration builder allowing further configuration of the component.</returns>
+        IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActivating(Func<IActivatingEventArgs<TLimit>, ValueTask> handler);
+
         /// <summary>
         /// Add a handler for the Activated event.
         /// </summary>
         /// <param name="handler">The event handler.</param>
         /// <returns>A registration builder allowing further configuration of the component.</returns>
         IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActivated(Action<IActivatedEventArgs<TLimit>> handler);
 
+        /// <summary>
+        /// Add a handler for the Activated event.
+        /// </summary>
+        /// <param name="handler">An event handler; the resolve process will not continue until the returned task completes.</param>
+        /// <returns>A registration builder allowing further configuration of the component.</returns>
+        IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActivated(Func<IActivatedEventArgs<TLimit>, ValueTask> handler);
+
         /// <summary>
         /// Configure the component so that any properties whose types are registered in the
         /// container and follow specific criteria will be wired to instances of the appropriate service.

src/Autofac/Builder/RegistrationBuilder{TLimit,TActivatorData,TRegistrationStyle}.cs

@@ -27,6 +27,7 @@
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
+using System.Threading.Tasks;
 using Autofac.Core;
 using Autofac.Core.Activators.Reflection;
 using Autofac.Core.Lifetime;
@@ -418,6 +419,25 @@ public IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnPrepar
             return this;
         }
 
+        /// <inheritdoc/>
+        public IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnPreparing(Func<PreparingEventArgs, ValueTask> handler)
+        {
+            if (handler == null)
+            {
+                throw new ArgumentNullException(nameof(handler));
+            }
+
+            return OnPreparing(args =>
+            {
+                var vt = handler(args);
+
+                if (!vt.IsCompletedSuccessfully)
+                {
+                    vt.ConfigureAwait(false).GetAwaiter().GetResult();
+                }
+            });
+        }
+
         /// <summary>
         /// Add a handler for the Activating event.
         /// </summary>
@@ -444,6 +464,25 @@ public IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActiva
             return this;
         }
 
+        /// <inheritdoc/>
+        public IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActivating(Func<IActivatingEventArgs<TLimit>, ValueTask> handler)
+        {
+            if (handler == null)
+            {
+                throw new ArgumentNullException(nameof(handler));
+            }
+
+            return OnActivating(args =>
+            {
+                var vt = handler(args);
+
+                if (!vt.IsCompletedSuccessfully)
+                {
+                    vt.ConfigureAwait(false).GetAwaiter().GetResult();
+                }
+            });
+        }
+
         /// <summary>
         /// Add a handler for the Activated event.
         /// </summary>
@@ -484,6 +523,25 @@ public IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActiva
             return this;
         }
 
+        /// <inheritdoc/>
+        public IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> OnActivated(Func<IActivatedEventArgs<TLimit>, ValueTask> handler)
+        {
+            if (handler == null)
+            {
+                throw new ArgumentNullException(nameof(handler));
+            }
+
+            return OnActivated(args =>
+            {
+                var vt = handler(args);
+
+                if (!vt.IsCompletedSuccessfully)
+                {
+                    vt.ConfigureAwait(false).GetAwaiter().GetResult();
+                }
+            });
+        }
+
         /// <summary>
         /// Configure the component so that any properties whose types are registered in the
         /// container and follow specific criteria will be wired to instances of the appropriate service.

src/Autofac/Core/Registration/ServiceRegistrationInfo.cs

@@ -45,7 +45,7 @@ internal class ServiceRegistrationInfo : IResolvePipelineBuilder
         [SuppressMessage("Microsoft.Performance", "CA1823:AvoidUnusedPrivateFields", Justification = "The _service field is useful in debugging and diagnostics.")]
         private readonly Service _service;
 
-        private IComponentRegistration? _fixedRegistration = null;
+        private IComponentRegistration? _fixedRegistration;
 
         /// <summary>
         ///  List of implicit default service implementations. Overriding default implementations are appended to the end,

src/Autofac/Core/Resolving/ResolveEventType.cs

@@ -8,7 +8,7 @@ namespace Autofac.Core.Resolving.Middleware
     public enum ResolveEventType
     {
         /// <summary>
-        /// Event type for the OnPreparing event registered by <see cref="IRegistrationBuilder{TLimit, TActivatorData, TRegistrationStyle}.OnPreparing"/>.
+        /// Event type for the OnPreparing event registered by <see cref="IRegistrationBuilder{TLimit, TActivatorData, TRegistrationStyle}.OnPreparing(System.Action{PreparingEventArgs})"/>.
         /// </summary>
         OnPreparing,
 
@@ -23,7 +23,7 @@ public enum ResolveEventType
         OnActivated,
 
         /// <summary>
-        /// Event type for the OnRelease event registered by <see cref="RegistrationExtensions.OnRelease"/>
+        /// Event type for the OnRelease event registered by <see cref="RegistrationExtensions.OnRelease{TLimit, TActivatorData, TRegistrationStyle}(IRegistrationBuilder{TLimit, TActivatorData, TRegistrationStyle}, System.Action{TLimit})"/>
         /// </summary>
         OnRelease
     }

src/Autofac/Core/Resolving/ResolveOperationBase.cs

@@ -41,8 +41,8 @@ public abstract class ResolveOperationBase : IResolveOperation
         private const int SuccessListInitialCapacity = 32;
 
         private bool _ended;
-        private List<ResolveRequestContext> _successfulRequests = new List<ResolveRequestContext>(SuccessListInitialCapacity);
-        private int _nextCompleteSuccessfulRequestStartPos = 0;
+        private readonly List<ResolveRequestContext> _successfulRequests = new List<ResolveRequestContext>(SuccessListInitialCapacity);
+        private int _nextCompleteSuccessfulRequestStartPos;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ResolveOperationBase"/> class.
@@ -179,6 +179,11 @@ protected object ExecuteOperation(ResolveRequest request)
         /// <inheritdoc />
         public object GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, ResolveRequest request)
         {
+            if (request is null)
+            {
+                throw new ArgumentNullException(nameof(request));
+            }
+
             if (_ended) throw new ObjectDisposedException(ResolveOperationResources.TemporaryContextDisposed, innerException: null);
 
             // Create a new request context.

src/Autofac/RegistrationExtensions.EventHandler.cs

@@ -25,6 +25,7 @@
 
 using System;
 using System.Diagnostics.CodeAnalysis;
+using System.Threading.Tasks;
 using Autofac.Builder;
 using Autofac.Core;
 using Autofac.Core.Resolving.Middleware;
@@ -94,7 +95,6 @@ public static IRegistrationBuilder<TLimit, ScanningActivatorData, TRegistrationS
         /// <param name="registration">Registration to set release action for.</param>
         /// <param name="releaseAction">An action to perform instead of disposing the instance.</param>
         /// <returns>Registration builder allowing the registration to be configured.</returns>
-        /// <remarks>Only one release action can be configured per registration.</remarks>
         public static IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle>
             OnRelease<TLimit, TActivatorData, TRegistrationStyle>(
                 this IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> registration,
@@ -124,5 +124,43 @@ public static IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle>
 
             return registration;
         }
+
+        /// <summary>
+        /// Run a supplied async action instead of disposing instances when they're no
+        /// longer required.
+        /// </summary>
+        /// <typeparam name="TLimit">Registration limit type.</typeparam>
+        /// <typeparam name="TActivatorData">Activator data type.</typeparam>
+        /// <typeparam name="TRegistrationStyle">Registration style.</typeparam>
+        /// <param name="registration">Registration to set release action for.</param>
+        /// <param name="releaseAction">
+        /// An action to perform instead of disposing the instance.
+        /// The release/disposal process will not continue until the returned task completes.
+        /// </param>
+        /// <returns>Registration builder allowing the registration to be configured.</returns>
+        public static IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle>
+            OnRelease<TLimit, TActivatorData, TRegistrationStyle>(
+                this IRegistrationBuilder<TLimit, TActivatorData, TRegistrationStyle> registration,
+                Func<TLimit, ValueTask> releaseAction)
+        {
+            if (registration == null) throw new ArgumentNullException(nameof(registration));
+            if (releaseAction == null) throw new ArgumentNullException(nameof(releaseAction));
+
+            registration.ExternallyOwned();
+
+            var middleware = new CoreEventMiddleware(ResolveEventType.OnRelease, PipelinePhase.Activation, (ctxt, next) =>
+            {
+                // Continue down the pipeline.
+                next(ctxt);
+
+                // Use an async release action that invokes the release callback in a proper async/await flow if someone
+                // is using actual async disposal.
+                ctxt.ActivationScope.Disposer.AddInstanceForAsyncDisposal(new AsyncReleaseAction<TLimit>(releaseAction, () => (TLimit)ctxt.Instance!));
+            });
+
+            registration.ResolvePipeline.Use(middleware, MiddlewareInsertionMode.StartOfPhase);
+
+            return registration;
+        }
     }
 }

src/Autofac/Util/AsyncReleaseAction.cs

@@ -0,0 +1,69 @@
+// Copyright (c) Autofac Project. All rights reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+using System;
+using System.Threading.Tasks;
+
+namespace Autofac.Util
+{
+    /// <summary>
+    /// Adapts an async action to the <see cref="IAsyncDisposable"/> interface.
+    /// </summary>
+    internal class AsyncReleaseAction<TLimit> : Disposable
+    {
+        private readonly Func<TLimit, ValueTask> _action;
+        private readonly Func<TLimit> _factory;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AsyncReleaseAction{TLimit}"/> class.
+        /// </summary>
+        /// <param name="action">
+        /// The async action to execute on disposal.
+        /// </param>
+        /// <param name="factory">
+        /// A factory that retrieves the value on which the <paramref name="action" />
+        /// should be executed.
+        /// </param>
+        public AsyncReleaseAction(Func<TLimit, ValueTask> action, Func<TLimit> factory)
+        {
+            if (action == null) throw new ArgumentNullException(nameof(action));
+            if (factory == null) throw new ArgumentNullException(nameof(factory));
+
+            _action = action;
+            _factory = factory;
+        }
+
+        /// <inheritdoc/>
+        protected override async ValueTask DisposeAsync(bool disposing)
+        {
+            // Value retrieval for the disposal is deferred until
+            // disposal runs to ensure any calls to, say, .ReplaceInstance()
+            // during .OnActivating() will be accounted for.
+            if (disposing)
+            {
+              await _action(_factory()).ConfigureAwait(false);
+            }
+
+            base.Dispose(disposing);
+        }
+
+        /// <inheritdoc/>
+        protected override void Dispose(bool disposing)
+        {
+            // Value retrieval for the disposal is deferred until
+            // disposal runs to ensure any calls to, say, .ReplaceInstance()
+            // during .OnActivating() will be accounted for.
+            if (disposing)
+            {
+                var vt = _action(_factory());
+
+                if (!vt.IsCompletedSuccessfully)
+                {
+                    vt.ConfigureAwait(false).GetAwaiter().GetResult();
+                }
+            }
+
+            base.Dispose(disposing);
+        }
+    }
+}