Raise.EventWith default constructor (#788)

src/NSubstitute/Core/Events/RaiseEventWrapper.cs

@@ -12,8 +12,8 @@ protected EventArgs GetDefaultForEventArgType(Type type)
     {
         if (type == typeof(EventArgs)) return EventArgs.Empty;
 
-        var defaultConstructor = GetDefaultConstructor(type);
-        if (defaultConstructor == null)
+        var defaultConstructor = GetPublicDefaultConstructor(type) ?? GetInternalDefaultConstructor(type);
+        if (defaultConstructor is null)
         {
             var message = string.Format(
                 "Cannot create {0} for this event as it has no default constructor. " +
@@ -24,7 +24,22 @@ protected EventArgs GetDefaultForEventArgType(Type type)
         return (EventArgs)defaultConstructor.Invoke([]);
     }
 
-    private static ConstructorInfo? GetDefaultConstructor(Type type) => type.GetConstructor(Type.EmptyTypes);
+    private static ConstructorInfo? GetInternalDefaultConstructor(Type type)
+    {
+        var nonPublicDefaultConstructor = GetNonPublicDefaultConstructor(type);
+        var isInternalDefaultConstructor = nonPublicDefaultConstructor?.IsAssembly == true;
+        return isInternalDefaultConstructor ? nonPublicDefaultConstructor : null;
+    }
+
+    private static ConstructorInfo? GetPublicDefaultConstructor(Type type)
+        => GetDefaultConstructor(type, BindingFlags.Public);
+
+    private static ConstructorInfo? GetNonPublicDefaultConstructor(Type type)
+        => GetDefaultConstructor(type, BindingFlags.NonPublic);
+
+    private static ConstructorInfo? GetDefaultConstructor(Type type, BindingFlags bindingFlags)
+        => type.GetConstructor(
+            BindingFlags.Instance | BindingFlags.ExactBinding | bindingFlags, null, Type.EmptyTypes, null);
 
     protected static void RaiseEvent(RaiseEventWrapper wrapper)
     {

tests/NSubstitute.Acceptance.Specs/EventRaising.cs

@@ -298,6 +298,31 @@
         Assert.That(eventRecorder.Sender, Is.SameAs(sender));
     }
 
+    [Test]
+    public void MyEvent_with_CustomEventArgsWithInternalDefaultConstructor_is_raised()
+    {
+        // Arrange
+        var exampleInternalMock = Substitute.For<IExampleInternal>();
+        var consumerInternal = new ConsumerInternal(exampleInternalMock);
+
+        // Act
+        exampleInternalMock.MyEvent += Raise.EventWith<CustomEventArgsWithInternalDefaultConstructor>(this, null!);
+
+        // Assert
+        Assert.That(consumerInternal.SomethingWasDone);
+    }
+
+    [Test]
+    public void MyEvent_with_CustomEventArgsWithPrivateDefaultConstructor_throws_CannotCreateEventArgsException()
+    {
+        // Arrange
+        var examplePrivateMock = Substitute.For<IExamplePrivate>();
+
+        // Act and Assert
+        Assert.Throws<CannotCreateEventArgsException>(() =>
+            examplePrivateMock.MyEvent += Raise.EventWith<CustomEventArgsWithPrivateDefaultConstructor>(this, null!));
+    }
+
     class RaisedEventRecorder<T>
     {
         public object Sender;
@@ -336,7 +361,41 @@
     public delegate int FuncDelegateWithArgs(int intArg, string stringArg);
     public delegate void CustomEventThatDoesNotInheritFromEventHandler(object sender, CustomEventArgs args);
     public class CustomEventArgs : EventArgs { }
     public class CustomEventArgsWithNoDefaultCtor(string arg) : EventArgs
     {
     }
+
+    public class CustomEventArgsWithInternalDefaultConstructor : EventArgs
+    {
+        internal CustomEventArgsWithInternalDefaultConstructor() { }
+    }
+    public interface IExampleInternal
+    {
+        public event EventHandler<CustomEventArgsWithInternalDefaultConstructor> MyEvent;
+    }
+    public class ConsumerInternal
+    {
+        public ConsumerInternal(IExampleInternal example)
+        {
+            example.MyEvent += OnMyEvent;
+        }
+        public bool SomethingWasDone { get; private set; }
+        private void OnMyEvent(object sender, CustomEventArgsWithInternalDefaultConstructor args)
+        {
+            DoSomething();
+        }
+        private void DoSomething()
+        {
+            SomethingWasDone = true;
+        }
+    }
+
+    public class CustomEventArgsWithPrivateDefaultConstructor : EventArgs
+    {
+        private CustomEventArgsWithPrivateDefaultConstructor() { }
+    }
+    public interface IExamplePrivate
+    {
+        public event EventHandler<CustomEventArgsWithPrivateDefaultConstructor> MyEvent;
+    }
 }