Avoiding discarding exception details of MissingMethodException in RuntimeType.CreateInstanceImpl

[Takym]

I found the code that try { ... } catch (MissingMethodException) { invokeMethod = null; } and immediately later, re-throwing MissingMethodException if invokeMethod was null. This code removes stack trace information. So, I think debugging or analyzing gets difficult. I kept the code throwing MissingMethodException because binder.BindToMethod may return null.

[kasperk81]

are there any tests that highlight the differences between the main branch and the pull request?

[Takym]

I have tested by below steps:

1. Build .NET Runtime
   1. Clone with the following command: git clone https://github.com/Takym/runtime.git -b AvoidingDiscardingExceptionDetails/2024_10
   2. Enter to the repository: cd runtime
   3. Run the build command: build
2. Install .NET Runtime
   1. Open the installer directory: explorer .\artifacts\packages\Debug\Shipping
   2. Execute following installers:
      • dotnet-runtime-10.0.0-dev-win-x64.exe
      • dotnet-apphost-pack-10.0.0-dev-win-x64.msi
      • dotnet-targeting-pack-10.0.0-dev-win-x64.msi
3. Create a new project with dotnet new console in a new empty directory.
4. Rewrite Program.cs:

   using System.Globalization;
   using System.Reflection;
   
   try {
   	Activator.CreateInstance(typeof(object), BindingFlags.CreateInstance, new MyBinder(), null, null, null);
   } catch (Exception e) {
   	Console.WriteLine(e.ToString());
   }
   
   class MyBinder : Binder
   {
   	public override MethodBase BindToMethod(BindingFlags bindingAttr, MethodBase[] match, ref object?[] args, ParameterModifier[]? modifiers, CultureInfo? culture, string[]? names, out object? state)
   		=> throw new MissingMethodException("Hello, World!!");
   
   	public override FieldInfo BindToField(BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo? culture)
   		=> throw new NotImplementedException();
   
   	public override object ChangeType(object value, Type type, CultureInfo? culture)
   		=> throw new NotImplementedException();
   
   	public override void ReorderArgumentArray(ref object?[] args, object state)
   		=> throw new NotImplementedException();
   
   	public override MethodBase? SelectMethod(BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[]? modifiers)
   		=> throw new NotImplementedException();
   
   	public override PropertyInfo? SelectProperty(BindingFlags bindingAttr, PropertyInfo[] match, Type? returnType, Type[]? indexes, ParameterModifier[]? modifiers)
   		=> throw new NotImplementedException();
   }

5. Running on .NET 9.0 or .NET 8.0: dotnet run

   System.MissingMethodException: Constructor on type 'System.Object' not found.
      at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
      at Program.<Main>$(String[] args)
   

6. Running on .NET 10.0-dev: dotnet run --roll-forward LatestMajor

   System.MissingMethodException: Constructor on type 'System.Object' not found.
    ---> System.MissingMethodException: Hello, World!!
      at MyBinder.BindToMethod(BindingFlags bindingAttr, MethodBase[] match, Object[]& args, ParameterModifier[] modifiers, CultureInfo culture, String[] names, Object& state)
      at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
      --- End of inner exception stack trace ---
      at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
      at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
      at Program.<Main>$(String[] args)
   

Key Differences

• My PR one contains all stack traces. So, it helps to analyze the error.
• Also, you can check the inner exception message. This means you can know the root cause of the error.
• I fixed this PR from no catching to rethrow for rewriting a message with the type's full name.
  • Initially, I removed the try-catch block to preserve the whole stack traces.
  • I got pointed out to include the original exception as an inner exception into a new exception to include the type full name.

[Takym]

You should uninstall .NET 10.0-dev after behavior testing for your computer safety.

[buyaa-n]

I have tested by below steps:

That looks great, thank you. Also adding a unit test would be great, you can add the test in https://github.com/dotnet/runtime/blob/main/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/ActivatorTests.cs

[kasperk81]

Also adding a unit test would be great

yeah, that's exactly what i was getting at, so we can prevent this behavior from popping up again in the future. adding a unit test would be great.

[Takym]

I added a unit test in the commit e4a8824. I have pushed the commit to test it online with CI. Testing offline (local PC) is not finished yet. I will be trying to run it later.

[steveharter]

Looks good; thanks!