From 3e752b226bc9bc3832a09f5b03adba9c1fd05750 Mon Sep 17 00:00:00 2001
From: dotnetjunkie <steven@cuttingedge.it>
Date: Thu, 7 Jan 2021 16:43:40 +0100
Subject: [PATCH] Improved exception messages thrown in case of type
 initialization errors. Fixes #812

---
 .../InstanceProducerTests.cs                  | 100 ++++++++++++++++++
 src/SimpleInjector/InstanceProducer.cs        |  37 ++++++-
 2 files changed, 134 insertions(+), 3 deletions(-)

diff --git a/src/SimpleInjector.Tests.Unit/InstanceProducerTests.cs b/src/SimpleInjector.Tests.Unit/InstanceProducerTests.cs
index 5804e5d5b..f03041df9 100644
--- a/src/SimpleInjector.Tests.Unit/InstanceProducerTests.cs
+++ b/src/SimpleInjector.Tests.Unit/InstanceProducerTests.cs
@@ -356,6 +356,98 @@ public void GetInstance_ForSingletonValueType_CanBeResolved()
             Assert.AreEqual(expectedValue, actualValue);
         }
 
+        // #812
+        [TestMethod]
+        public void GetInstance_ResolvingATypeWithTypeInitializationException_ThrowsExpressiveException()
+        {
+            // Act
+            var container = new Container();
+
+            container.Register<TopLevelClassWithFailingTypeInitializer>();
+
+            // Act
+            Action action = () => container.GetInstance<TopLevelClassWithFailingTypeInitializer>();
+
+            // Assert
+            AssertThat.ThrowsWithExceptionMessageContains<ActivationException>(
+                "The type initializer for TopLevelClassWithFailingTypeInitializer threw an " +
+                "exception. <Inner exception>.",
+                action);
+        }
+
+        // #812
+        [TestMethod]
+        public void GetInstance_ResolvingANestedTypeWithTypeInitializationException_ThrowsExpressiveException()
+        {
+            // Act
+            var container = new Container();
+
+            container.Register<NestedClassWithFailingTypeInitializer>();
+
+            // Act
+            Action action = () => container.GetInstance<NestedClassWithFailingTypeInitializer>();
+
+            // Assert
+            AssertThat.ThrowsWithExceptionMessageContains<ActivationException>(
+                "The type initializer for InstanceProducerTests.NestedClassWithFailingTypeInitializer " +
+                "threw an exception. <Inner exception>.",
+                action);
+        }
+
+        // #812
+        [TestMethod]
+        public void GetInstance_ResolvingAGenericNestedTypeWithTypeInitializationException_ThrowsExpressiveException()
+        {
+            // Act
+            var container = new Container();
+
+            container.Register(typeof(NestedClassWithFailingTypeInitializer<>));
+
+            // Act
+            Action action = () => container.GetInstance<NestedClassWithFailingTypeInitializer<object>>();
+
+            // Assert
+            AssertThat.ThrowsWithExceptionMessageContains<ActivationException>(
+                "The type initializer for InstanceProducerTests" +
+                ".NestedClassWithFailingTypeInitializer<object> threw an exception. <Inner exception>.",
+                action);
+        }
+
+        // #812
+        [TestMethod]
+        public void GetInstance_ResolvingASingletonWithTypeInitializationException_ThrowsExpressiveException()
+        {
+            // Act
+            var container = new Container();
+
+            container.RegisterSingleton<NestedClassWithFailingTypeInitializer>();
+
+            // Act
+            Action action = () => container.GetInstance<NestedClassWithFailingTypeInitializer>();
+
+            // Assert
+            AssertThat.ThrowsWithExceptionMessageContains<ActivationException>(
+                "The type initializer for InstanceProducerTests.NestedClassWithFailingTypeInitializer " +
+                "threw an exception. <Inner exception>.",
+                action);
+        }
+
+        public class NestedClassWithFailingTypeInitializer
+        {
+            static NestedClassWithFailingTypeInitializer()
+            {
+                throw new Exception("<Inner exception>.");
+            }
+        }
+
+        public class NestedClassWithFailingTypeInitializer<T>
+        {
+            static NestedClassWithFailingTypeInitializer()
+            {
+                throw new Exception("<Inner exception>.");
+            }
+        }
+
         public class OneAndTwo : IOne, ITwo
         {
         }
@@ -381,4 +473,12 @@ public NodeFactory(IEnumerable<INode> nodes)
             }
         }
     }
+
+    public class TopLevelClassWithFailingTypeInitializer
+    {
+        static TopLevelClassWithFailingTypeInitializer()
+        {
+            throw new Exception("<Inner exception>.");
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/SimpleInjector/InstanceProducer.cs b/src/SimpleInjector/InstanceProducer.cs
index 1a669a3ec..d413183f3 100644
--- a/src/SimpleInjector/InstanceProducer.cs
+++ b/src/SimpleInjector/InstanceProducer.cs
@@ -329,6 +329,10 @@ public Expression BuildExpression()
 
                 throw;
             }
+            catch (TypeInitializationException ex)
+            {
+                throw this.MakeMoreExpressiveTypeInitializationException(ex);
+            }
             catch (Exception ex)
             {
                 if (this.MustWrapThrownException(ex))
@@ -610,9 +614,17 @@ private string BuildActivationExceptionMessage(Exception innerException)
         private object BuildAndReplaceInstanceCreatorAndCreateFirstInstance()
         {
             this.instanceCreator = this.BuildInstanceCreator();
-            var instance = this.instanceCreator();
-            this.InstanceSuccessfullyCreated = true;
-            return instance;
+
+            try
+            {
+                var instance = this.instanceCreator();
+                this.InstanceSuccessfullyCreated = true;
+                return instance;
+            }
+            catch (TypeInitializationException ex)
+            {
+                throw this.MakeMoreExpressiveTypeInitializationException(ex);
+            }
         }
 
         // Prevents any recursive calls from taking place.
@@ -674,6 +686,25 @@ private static bool ShouldBeRegisteredAsAnExternalProducer(Registration registra
             return !(registration is ExpressionRegistration);
         }
 
+        private Exception MakeMoreExpressiveTypeInitializationException(
+            TypeInitializationException ex)
+        {
+            Type implementationType = this.Registration.ImplementationType;
+
+            // #812 The exceptions thrown by the runtime in case of a type initialization error are
+            // unproductive. Here we throw a more expressive exception. This is done by appending the
+            // inner exception's message to the exception message and replacing the type name with a
+            // 'friendly type name', which is especially useful in the case of generic types.
+            return new ActivationException(
+                ex.Message
+                    // When the type in question is nested, the exception will contain just the simple
+                    // type name, while for non-nested types, the full name is used (don't ask why).
+                    .Replace($"'{implementationType.FullName}'", implementationType.ToFriendlyName())
+                    .Replace($"'{implementationType.Name}'", implementationType.ToFriendlyName()) +
+                    " " + ex.InnerException?.Message,
+                ex);
+        }
+
         [ExcludeFromCodeCoverage]
         internal sealed class InstanceProducerDebugView
         {