trying to generate a type with a delegate crashes dotnet

[hahn-kev]

I came across this when trying to generate a bunch of types
exception

Fatal error. Internal CLR error. (0x80131506)
   at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(System.Object, System.Span`1<System.Object>, System.Reflection.BindingFlags)
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)
   at System.Reflection.RuntimeConstructorInfo.Invoke(System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)
   at System.Reflection.ConstructorInfo.Invoke(System.Object[])
   at Soenneker.Reflection.Cache.Constructors.CachedConstructor.Invoke(System.Object[])
   at Soenneker.Utils.AutoBogus.AutoFakerBinder.CreateInstance[[System.__Canon, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]](Soenneker.Utils.AutoBogus.Context.AutoFakerContext, Soenneker.Reflection.Cache.Types.CachedType)
   at Soenneker.Utils.AutoBogus.AutoFakerBinder.CreateInstanceWithRecursionGuard[[System.__Canon, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]](Soenneker.Utils.AutoBogus.Context.AutoFakerContext, Soenneker.Reflection.Cache.Types.CachedType)
   at Soenneker.Utils.AutoBogus.Generators.Types.TypeGenerator`1[[System.__Canon, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].Soenneker.Utils.AutoBogus.Generators.Abstract.IAutoFakerGenerator.Generate(Soenneker.Utils.AutoBogus.Context.AutoFakerContext)
   at Soenneker.Utils.AutoBogus.Extensions.AutoGenerateContextExtension.Generate[[System.__Canon, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]](Soenneker.Utils.AutoBogus.Context.AutoFakerContext)
   at Soenneker.Utils.AutoBogus.AutoFaker.Generate[[System.__Canon, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]()
   at LcmCrdt.Tests.Changes.ChangeSerializationTests.FindBadType()

something as simple as this will reproduce the crash:

new AutoFaker().Generate<Action<string>>();

I don't think generating Actions is even possible or should be supported, but I do think a good error should be thrown, In my case I was trying to generate a bunch of types and it was quite difficult to track down the offender because I didn't know what was going on. A simple test like type.IsAssignableTo(typeof(Delegate) should work in my testing.

[soenneker]

I fixed some types like this recently, I'm surprised this got through. Thanks for the replication, I'll check it out.

[soenneker]

@hahn-kev are you using the latest version? I've tested this and it doesn't exception.

[hahn-kev]

I'm so sorry, I did not try the latest version, we updated last month so I didn't think to check for a newer version. It does not crash anymore, however it just returns null which I didn't expect as it's not annotated to return null. I would prefer to configure it to throw an exception if it can't generate a type for some reason, would that be possible? This is especially important when generating an object graph and some dependency deep down can't be generated.

[soenneker]

@hahn-kev perhaps that's an option that could be added (e.g. ThrowIfCannotGenerate) ... I'm leery of making the return types all nullable. Thoughts?

[hahn-kev]

I kinda feel like if it can return null then the API should communicate that to the developer. If I don't know then my code will throw at some point when it tries to use it. Your code can throw early or my code can throw later.

[soenneker]

@hahn-kev I wanted to make sure you're clear that even if we mark the generate() method as possibly returning null, it might generate a top level object with an instance but downstream objects could still be null. Does the nullable return value still help you considering this?

[hahn-kev]

Not really, which is why I would still want an option to throw, otherwise a test might fail or code throw when something is null that shouldn't be null.