Add policy factory overloads for pooled instance registration

.gitignore

@@ -166,3 +166,6 @@ $RECYCLE.BIN/
 
 # JetBrains Rider
 .idea
+
+# Reasonix AI assistant
+.reasonix/

src/Autofac.Pooling/PoolActivator.cs

@@ -15,12 +15,14 @@ namespace Autofac.Pooling;
 internal sealed class PoolActivator<TLimit> : IInstanceActivator
     where TLimit : class
 {
-    private readonly Service _pooledInstanceService;
-    private readonly IPooledRegistrationPolicy<TLimit> _policy;
-    private readonly DefaultObjectPoolProvider _poolProvider;
+    private readonly Service? _pooledInstanceService;
+    private readonly IPooledRegistrationPolicy<TLimit>? _policy;
+    private readonly DefaultObjectPoolProvider? _poolProvider;
+    private readonly Func<IComponentContext, IPooledRegistrationPolicy<TLimit>>? _policyFactory;
 
     /// <summary>
-    /// Initializes a new instance of the <see cref="PoolActivator{TLimit}"/> class.
+    /// Initializes a new instance of the <see cref="PoolActivator{TLimit}"/> class
+    /// using the default <see cref="DefaultObjectPoolProvider"/>.
     /// </summary>
     /// <param name="pooledInstanceService">The service used to resolve new instances of the pooled registration.</param>
     /// <param name="policy">The pool policy.</param>
@@ -34,6 +36,23 @@ public PoolActivator(Service pooledInstanceService, IPooledRegistrationPolicy<TL
         };
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="PoolActivator{TLimit}"/> class
+    /// using a factory function to create the <see cref="IPooledRegistrationPolicy{TLimit}"/> at resolve time.
+    /// The default <see cref="DefaultObjectPoolProvider"/> will create the backing pool.
+    /// </summary>
+    /// <param name="pooledInstanceService">The service used to resolve new instances of the pooled registration.</param>
+    /// <param name="policyFactory">
+    /// A factory that returns the <see cref="IPooledRegistrationPolicy{TLimit}"/> to use.
+    /// Invoked during resolve, so the <see cref="IComponentContext"/> is available
+    /// for resolving dependencies.
+    /// </param>
+    public PoolActivator(Service pooledInstanceService, Func<IComponentContext, IPooledRegistrationPolicy<TLimit>> policyFactory)
+    {
+        _pooledInstanceService = pooledInstanceService;
+        _policyFactory = policyFactory ?? throw new ArgumentNullException(nameof(policyFactory));
+    }
+
     /// <inheritdoc/>
     public Type LimitType { get; } = typeof(TLimit);
 
@@ -42,15 +61,31 @@ public void ConfigurePipeline(IComponentRegistryServices componentRegistryServic
     {
         pipelineBuilder.Use(PipelinePhase.Activation, (context, next) =>
         {
-            // Get a reference to the actual lifetime scope.
-            var scope = context.Resolve<ILifetimeScope>();
+            if (_policyFactory is not null)
+            {
+                // Custom policy factory: resolve the strategy at resolve time, then create DefaultObjectPool.
+                var policy = _policyFactory(context);
+                var poolProvider = new DefaultObjectPoolProvider
+                {
+                    MaximumRetained = policy.MaximumRetained,
+                };
+                var scope = context.Resolve<ILifetimeScope>();
+                var poolPolicy = new AutofacPooledObjectPolicy<TLimit>(_pooledInstanceService!, scope, policy);
+                var pool = poolProvider.Create(poolPolicy);
+                context.Instance = new PooledInstanceContext<TLimit>(pool, policy);
+            }
+            else
+            {
+                // Default path: use DefaultObjectPoolProvider + AutofacPooledObjectPolicy.
+                var scope = context.Resolve<ILifetimeScope>();
 
-            var poolPolicy = new AutofacPooledObjectPolicy<TLimit>(_pooledInstanceService, scope, _policy);
+                var poolPolicy = new AutofacPooledObjectPolicy<TLimit>(_pooledInstanceService!, scope, _policy!);
 
-            // The pool provider will create a disposable pool if the TLimit implements IDisposable.
-            var pool = _poolProvider.Create(poolPolicy);
+                // The pool provider will create a disposable pool if the TLimit implements IDisposable.
+                var pool = _poolProvider!.Create(poolPolicy);
 
-            context.Instance = pool;
+                context.Instance = pool;
+            }
         });
     }
 

src/Autofac.Pooling/PoolGetActivator.cs

@@ -17,7 +17,7 @@ internal sealed class PoolGetActivator<TLimit> : IInstanceActivator
     where TLimit : class
 {
     private readonly PoolService _poolService;
-    private readonly IPooledRegistrationPolicy<TLimit> _registrationPolicy;
+    private readonly IPooledRegistrationPolicy<TLimit>? _registrationPolicy;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="PoolGetActivator{TLimit}"/> class.
@@ -30,6 +30,16 @@ public PoolGetActivator(PoolService poolService, IPooledRegistrationPolicy<TLimi
         _registrationPolicy = registrationPolicy;
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="PoolGetActivator{TLimit}"/> class.
+    /// The policy will be retrieved from the <see cref="PooledInstanceContext{TLimit}"/> at resolve time.
+    /// </summary>
+    /// <param name="poolService">The service used to access the pool.</param>
+    public PoolGetActivator(PoolService poolService)
+    {
+        _poolService = poolService;
+    }
+
     /// <inheritdoc/>
     public Type LimitType { get; } = typeof(TLimit);
 
@@ -38,7 +48,10 @@ public void ConfigurePipeline(IComponentRegistryServices componentRegistryServic
     {
         pipelineBuilder.Use(PipelinePhase.Activation, (ctxt, next) =>
         {
-            var pool = (ObjectPool<TLimit>)ctxt.ResolveService(_poolService);
+            var resolved = ctxt.ResolveService(_poolService);
+            var ctx = resolved as PooledInstanceContext<TLimit>;
+            var pool = ctx is not null ? ctx.Pool : (ObjectPool<TLimit>)resolved;
+            var policy = ctx is not null ? ctx.Policy : _registrationPolicy!;
             var didGetFromPool = false;
 
             TLimit PoolGet()
@@ -47,11 +60,11 @@ TLimit PoolGet()
                 return pool.Get();
             }
 
-            var poolItem = _registrationPolicy.Get(ctxt, ctxt.Parameters, PoolGet) ?? throw new InvalidOperationException(
+            var poolItem = policy.Get(ctxt, ctxt.Parameters, PoolGet) ?? throw new InvalidOperationException(
                     string.Format(
                         CultureInfo.CurrentCulture,
                         PoolGetActivatorResources.PolicyMustReturnInstance,
-                        _registrationPolicy.GetType().FullName,
+                        policy.GetType().FullName,
                         typeof(TLimit).FullName));
 
             if (didGetFromPool)

src/Autofac.Pooling/PooledInstanceContext.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Autofac Project. All rights reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+using Microsoft.Extensions.ObjectPool;
+
+namespace Autofac.Pooling;
+
+/// <summary>
+/// Holds a resolved pool and its associated policy instance,
+/// so the policy created during pool construction is shared with the get-side activator.
+/// </summary>
+/// <typeparam name="TLimit">The limit type of the objects in the pool.</typeparam>
+internal sealed class PooledInstanceContext<TLimit>
+    where TLimit : class
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="PooledInstanceContext{TLimit}"/> class.
+    /// </summary>
+    /// <param name="pool">The object pool.</param>
+    /// <param name="policy">The resolved registration policy.</param>
+    public PooledInstanceContext(ObjectPool<TLimit> pool, IPooledRegistrationPolicy<TLimit> policy)
+    {
+        Pool = pool;
+        Policy = policy;
+    }
+
+    /// <summary>
+    /// Gets the object pool.
+    /// </summary>
+    public ObjectPool<TLimit> Pool
+    {
+        get;
+    }
+
+    /// <summary>
+    /// Gets the resolved registration policy, shared between pool creation and retrieval.
+    /// </summary>
+    public IPooledRegistrationPolicy<TLimit> Policy
+    {
+        get;
+    }
+}