Added better exceptions to the service factory. (#1040)

src/Core/Utilities.Tests/ServiceFactoryTests.cs

@@ -1,4 +1,5 @@
 using System;
+using Snapshooter.Xunit;
 using Xunit;
 
 namespace HotChocolate.Utilities
@@ -57,6 +58,52 @@ public void CreateInstanceWithServiceProvider()
             Assert.NotNull(classWithDependencies.Dependency);
         }
 
+        [Fact]
+        public void Catch_Exception_On_Create()
+        {
+            // arrange
+            var factory = new ServiceFactory();
+            var type = typeof(ClassWithNoException);
+
+            // act
+            Action action = () => factory.CreateInstance(type);
+
+            // assert
+            Assert.Throws<CreateServiceException>(action)
+                .Message.MatchSnapshot();
+        }
+
+        [Fact]
+        public void Cannot_Resolve_Dependencies()
+        {
+            // arrange
+            var factory = new ServiceFactory();
+            factory.Services = new EmptyServiceProvider();
+            var type = typeof(ClassWithDependencies);
+
+            // act
+            Action action = () => factory.CreateInstance(type);
+
+            // assert
+            Assert.Throws<CreateServiceException>(action)
+                .Message.MatchSnapshot();
+        }
+
+        [Fact]
+        public void No_Services_Available()
+        {
+            // arrange
+            var factory = new ServiceFactory();
+            var type = typeof(ClassWithDependencies);
+
+            // act
+            Action action = () => factory.CreateInstance(type);
+
+            // assert
+            Assert.Throws<CreateServiceException>(action)
+                .Message.MatchSnapshot();
+        }
+
         private class ClassWithNoDependencies
         {
         }
@@ -70,5 +117,13 @@ public ClassWithDependencies(ClassWithNoDependencies dependency)
 
             public ClassWithNoDependencies Dependency { get; }
         }
+
+        private class ClassWithNoException
+        {
+            public ClassWithNoException()
+            {
+                throw new NullReferenceException();
+            }
+        }
     }
 }

src/Core/Utilities.Tests/__snapshots__/ServiceFactoryTests.Cannot_Resolve_Dependencies.snap

@@ -0,0 +1 @@
+Unable to find a constructor on type `HotChocolate.Utilities.ServiceFactoryTests+ClassWithDependencies` that can be fulfilled with the currently available set of services. Check if all dependent services for this type are registered.

src/Core/Utilities.Tests/__snapshots__/ServiceFactoryTests.Catch_Exception_On_Create.snap

@@ -0,0 +1 @@
+Unable to create service `HotChocolate.Utilities.ServiceFactoryTests+ClassWithNoException` see inner exception for more details.

src/Core/Utilities.Tests/__snapshots__/ServiceFactoryTests.No_Services_Available.snap

@@ -0,0 +1 @@
+The instance type `HotChocolate.Utilities.ServiceFactoryTests+ClassWithDependencies` must have a parameterless constructor .

src/Core/Utilities/CreateServiceException.cs

@@ -0,0 +1,25 @@
+using System;
+
+namespace HotChocolate.Utilities
+{
+#if !NETSTANDARD1_4
+    [Serializable]
+#endif
+    public class CreateServiceException
+        : Exception
+    {
+        public CreateServiceException()
+        {
+        }
+
+        public CreateServiceException(string message)
+            : base(message)
+        {
+        }
+
+        public CreateServiceException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+    }
+}

src/Core/Utilities/ServiceFactory.cs

@@ -12,19 +12,22 @@ public class ServiceFactory
 
         public object CreateInstance(Type type)
         {
-            if (type == null)
+            if (type is null)
             {
                 throw new ArgumentNullException(nameof(type));
             }
 
             object service = Services?.GetService(type);
+
             if (service != null)
             {
                 return service;
             }
 
+
 #if NETSTANDARD1_4
-            if (type.GetTypeInfo().IsInterface || type.GetTypeInfo().IsAbstract)
+            TypeInfo typeInfo = type.GetTypeInfo();
+            if (typeInfo.IsInterface || typeInfo.IsAbstract)
 #else
             if (type.IsInterface || type.IsAbstract)
 #endif
@@ -33,17 +36,26 @@ public object CreateInstance(Type type)
             }
 
             FactoryInfo factoryInfo = CreateFactoryInfo(Services, type);
-            ParameterInfo[] parameters =
-                factoryInfo.Constructor.GetParameters();
+            ParameterInfo[] parameters = factoryInfo.Constructor.GetParameters();
             object[] arguments = new object[parameters.Length];
 
             for (int i = 0; i < parameters.Length; i++)
             {
-                arguments[i] =
-                    factoryInfo.Arguments[parameters[i].ParameterType];
+                arguments[i] = factoryInfo.Arguments[parameters[i].ParameterType];
             }
 
-            return factoryInfo.Constructor.Invoke(arguments);
+            try
+            {
+                return factoryInfo.Constructor.Invoke(arguments);
+            }
+            catch (Exception ex)
+            {
+                // TODO : Resource
+                throw new CreateServiceException(
+                    $"Unable to create service `{type.FullName}`" +
+                    " see inner exception for more details.",
+                    ex);
+            }
         }
 
         object IServiceProvider.GetService(Type serviceType) =>
@@ -65,26 +77,40 @@ private static FactoryInfo CreateFactoryInfo(
 
             if (constructors.Length == 0)
             {
-                throw new InvalidOperationException(
+                // TODO : Resource
+                throw new CreateServiceException(
                     $"The instance type `{type.FullName}` " +
                     "must have at least on public constructor.");
             }
 
-            if (services == null)
+            if (services is null)
             {
                 ConstructorInfo constructor = constructors
                     .FirstOrDefault(t => !t.GetParameters().Any());
-                if (constructor == null)
+                if (constructor is null)
                 {
-                    throw new InvalidOperationException(
+                    // TODO : Resource
+                    throw new CreateServiceException(
                         $"The instance type `{type.FullName}` " +
                         "must have a parameterless constructor .");
                 }
                 return new FactoryInfo(type, constructor);
             }
 
-            return GetBestMatchingConstructor(
+            FactoryInfo factoryInfo = GetBestMatchingConstructor(
                 services, type, constructors);
+
+            if (factoryInfo is null)
+            {
+                // TODO : Resource
+                throw new CreateServiceException(
+                    $"Unable to find a constructor on type `{type.FullName}` " +
+                    "that can be fulfilled with the currently " +
+                    "available set of services. Check if " +
+                    "all dependent services for this type are registered.");
+            }
+
+            return factoryInfo;
         }
 
         private static FactoryInfo GetBestMatchingConstructor(