From 1a012c5d493dd31aceea8fe29f23a2d58d252a11 Mon Sep 17 00:00:00 2001
From: Alexandru Macocian <almacoci@microsoft.com>
Date: Thu, 3 Jun 2021 13:03:29 +0200
Subject: [PATCH] Scoped ServiceManager calls original ServiceManager when
 resolving singletons

---
 LICENSE                           |  2 +-
 Slim.Tests/MemoryLeakTests.cs     | 45 +++++++++++++++++++++++++++++++
 Slim.Tests/ServiceManagerTests.cs |  2 +-
 Slim/ServiceManager.cs            | 22 ++++++++++++---
 Slim/Slim.csproj                  |  6 ++---
 5 files changed, 68 insertions(+), 9 deletions(-)
 create mode 100644 Slim.Tests/MemoryLeakTests.cs

diff --git a/LICENSE b/LICENSE
index 5844c61..7b4b612 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2020 Macocian Alexandru Victor
+Copyright (c) 2021 Macocian Alexandru Victor
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/Slim.Tests/MemoryLeakTests.cs b/Slim.Tests/MemoryLeakTests.cs
new file mode 100644
index 0000000..8a5b7ab
--- /dev/null
+++ b/Slim.Tests/MemoryLeakTests.cs
@@ -0,0 +1,45 @@
+using FluentAssertions;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Slim.Tests.Models;
+using System;
+using System.Threading.Tasks;
+
+namespace Slim.Tests
+{
+    [TestClass]
+    public sealed class MemoryLeakTests
+    {
+        private const int ScopesCount = 10000;
+
+        [TestMethod]
+        public async Task CreateAndReleaseScopesDisposeManagerGCCollects()
+        {
+            var di = new ServiceManager();
+            di.RegisterSingleton<IIndependentService, IndependentService>();
+            di.RegisterScoped<IDependentService, DependentService>();
+            var independentService = di.GetService<IIndependentService>();
+            var dependentService = di.GetService<IDependentService>();
+
+            var weakRefs = new WeakReference[ScopesCount];
+            for (int i = 0; i < ScopesCount; i++)
+            {
+                var scopedDi = di.CreateScope();
+                weakRefs[i] = new WeakReference(scopedDi);
+                var scopedDependentService = scopedDi.GetService<IDependentService>();
+                scopedDependentService.Should().NotBeNull();
+                scopedDependentService.Should().NotBe(dependentService);
+                scopedDependentService.IndependentService.Should().NotBeNull();
+                scopedDependentService.IndependentService.Should().Be(independentService);
+            }
+
+            await Task.Delay(1500);
+            GC.Collect();
+            GC.WaitForPendingFinalizers();
+            GC.Collect();
+            foreach(var weakRef in weakRefs)
+            {
+                weakRef.IsAlive.Should().BeFalse();
+            }
+        }
+    }
+}
diff --git a/Slim.Tests/ServiceManagerTests.cs b/Slim.Tests/ServiceManagerTests.cs
index c349022..3dad0f0 100644
--- a/Slim.Tests/ServiceManagerTests.cs
+++ b/Slim.Tests/ServiceManagerTests.cs
@@ -429,9 +429,9 @@ namespace Slim.Tests
         {
             var di = new ServiceManager();
             di.RegisterSingleton<IIndependentService, IndependentService>();
+            var scopedDi = di.CreateScope();
 
             var service = di.GetService<IIndependentService>();
-            var scopedDi = di.CreateScope();
             var scopedService = scopedDi.GetService<IIndependentService>();
 
             service.Should().Be(scopedService);
diff --git a/Slim/ServiceManager.cs b/Slim/ServiceManager.cs
index 99eacb2..9fb0009 100644
--- a/Slim/ServiceManager.cs
+++ b/Slim/ServiceManager.cs
@@ -673,7 +673,7 @@ namespace Slim
             var dictionary = new Dictionary<Type, object>();
             foreach (var kvp in this.Instances)
             {
-                if (this.InterfaceMapping.First(s => s.Value.Item1 == kvp.Key).Value.Item2 is not Lifetime.Scoped)
+                if (this.InterfaceMapping.First(s => s.Value.Item1 == kvp.Key).Value.Item2 is Lifetime.Singleton)
                 {
                     dictionary.Add(kvp.Key, kvp.Value);
                 }
@@ -687,8 +687,22 @@ namespace Slim
             var factories = new Dictionary<Type, Delegate>(this.Factories);
             var exceptionHandlers = new Dictionary<Type, Delegate>(this.ExceptionHandlers);
             var resolvers = new List<IDependencyResolver>(this.Resolvers);
-            var singletons = this.GetSingletons();
-            return new ServiceManager(interfaceMapping, singletons, factories, exceptionHandlers, resolvers);
+            /*
+             * For singletons, create a factory in scoped service manager that should call this manager
+             * to retrieve the singleton.
+             * This means that if the singleton has not yet been created in this service manager,
+             * the scoped service manager will not create a new one but instead ask the original service manager to
+             * create the singleton instead.
+             */
+            foreach (var kvp in this.InterfaceMapping)
+            {
+                if (kvp.Value.Item2 is Lifetime.Singleton)
+                {
+                    factories[kvp.Key] = new Func<IServiceProvider, object>((_) => this.PrepareAndGetService(kvp.Key));
+                }
+            }
+
+            return new ServiceManager(interfaceMapping, new Dictionary<Type, object>(), factories, exceptionHandlers, resolvers);
         }
     }
-}
+}
\ No newline at end of file
diff --git a/Slim/Slim.csproj b/Slim/Slim.csproj
index 35271e7..52da80a 100644
--- a/Slim/Slim.csproj
+++ b/Slim/Slim.csproj
@@ -8,10 +8,10 @@
     <Company />
     <Product></Product>
     <Description>Service lifetime management and dependency injection framework.</Description>
-    <AssemblyVersion>1.4.2.0</AssemblyVersion>
-    <FileVersion>1.4.2.0</FileVersion>
+    <AssemblyVersion>1.4.3.0</AssemblyVersion>
+    <FileVersion>1.4.3.0</FileVersion>
     <PackageProjectUrl>https://github.com/AlexMacocian/Slim</PackageProjectUrl>
-    <Version>1.4.2</Version>
+    <Version>1.4.3</Version>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>