Fixing IServiceProvider.GetService implementation (fixes #376) (#377)

* Fixing IServiceProvider.GetService implementation (fixes #376)

* Added a configuration option to restore the old behavior if necessary

src/Ninject.Test/Integration/StandardKernelTests.cs

@@ -567,7 +567,40 @@ public void ItCanBeResolved()
             }
         }
     }
-
+
+    public class WhenServiceIsResolvedThroughServiceProviderInterface : StandardKernelContext
+    {
+        [Fact]
+        public void ItResolvesBoundService()
+        {
+            this.kernel.Bind<IWeapon>().To<Sword>();
+
+            var provider = this.kernel as IServiceProvider;
+            provider.GetService(typeof(IWeapon)).Should().NotBeNull();
+        }
+
+        [Fact]
+        public void ItReturnsNullWhenServiceIsNotConfigured()
+        {
+            var provider = this.kernel as IServiceProvider;
+            provider.GetService(typeof(Samurai)).Should().BeNull();
+        }
+
+        [Fact]
+        public void ItThrowsWhenServiceIsNotConfiguredAndSettingThrowOnGetServiceNotFound()
+        {
+            using (var kernel = new StandardKernel(new NinjectSettings
+            {
+                ThrowOnGetServiceNotFound = true
+            }))
+            {
+                var provider = kernel as IServiceProvider;
+                Action resolveAction = () => provider.GetService(typeof(Samurai));
+                resolveAction.ShouldThrow<ActivationException>();
+            }
+        }
+    }
+
     public class InitializableA : IInitializable
     {
         public static int Count = 0;

src/Ninject/INinjectSettings.cs

@@ -96,6 +96,14 @@ public interface INinjectSettings
         /// <value><c>true</c> if null is allowed as injected value otherwise false.</value>
         bool AllowNullInjection { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether the old (&lt;= 3.3.4) behavior of <see cref="IServiceProvider.GetService(Type)"/>
+        /// should be used which throws an exception if the requested service cannot be found. Note that the documentation
+        /// of that method https://docs.microsoft.com/en-us/dotnet/api/system.iserviceprovider.getservice?view=netframework-4.6.2
+        /// states that the method should return <see langword="null"/> if there is no such service.
+        /// </summary>
+        bool ThrowOnGetServiceNotFound { get; set; }
+
         /// <summary>
         /// Gets the value for the specified key.
         /// </summary>

src/Ninject/KernelBase.cs

@@ -411,7 +411,9 @@ public virtual IEnumerable<IBinding> GetBindings(Type service)
         /// <returns>The service object</returns>
         object IServiceProvider.GetService(Type service)
         {
-            return this.Get(service);
+            return this.Settings.ThrowOnGetServiceNotFound
+               ? this.Get(service)
+               : this.TryGet(service);
         }
 
         /// <summary>

src/Ninject/NinjectSettings.cs

@@ -142,6 +142,14 @@ public bool AllowNullInjection
             set { this.Set("AllowNullInjection", value); }
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether the old (&lt;= 3.3.4) behavior of <see cref="IServiceProvider.GetService(Type)"/>
+        /// should be used which thorows an exception if the requested service cannot be found. Note that the documentation
+        /// of that method https://docs.microsoft.com/en-us/dotnet/api/system.iserviceprovider.getservice?view=netframework-4.6.2
+        /// states that the method should return <see langword="null"/> if there is no such service.
+        /// </summary>
+        public bool ThrowOnGetServiceNotFound { get; set; }
+
         /// <summary>
         /// Gets the value for the specified key.
         /// </summary>