Whitelist(/Add an alternative) System.Linq.Expressions request

[Manonox]

Issue posted half a year ago - #131
Closed, but I guess everyone forgot about it
Some people need System.Linq.Expressions for stuff
For me it is MoonSharp, it uses it in descriptors
Any alternative can work fine too probably

[Rohansi]

Unfortunately System.Linq.Expressions is a huge namespace which we can't possibly just whitelist because it's full of possible holes to escape sandboxing. There's a ton of possible use cases for it so it'd be worth bringing up specific things that need alternatives to.

Could you summarize what MoonSharp uses it for?

[Manonox]

Could you summarize what MoonSharp uses it for?

The type or namespace name 'Expressions' does not exist in the namespace 'System.Linq' (are you missing an assembly reference?)
moonsharp\Interop\StandardDescriptors\ReflectionMemberDescriptors\FieldMemberDescriptor.cs(2,19): error CS0234: ...
moonsharp\Interop\StandardDescriptors\ReflectionMemberDescriptors\MethodMemberDescriptor.cs(4,19): error CS0234: ...
moonsharp\Interop\StandardDescriptors\ReflectionMemberDescriptors\PropertyMemberDescriptor.cs(2,19): error CS0234: ...

FieldMemberDescriptor.cs
MethodMemberDescriptor.cs
PropertyMemberDescriptor.cs

Actual Expression stuff used in code:
Expression.Parameter
Expression.Field
Expression.Convert
Expression.Lambda
Expression.ArrayIndex
Expression.Constant
Expression.Call

I am not that knowledgeable in C#'s various namespaces(libraries) and Interop structures, so that's all I have

There are other things that break moonsharp, but they are fixable (for example platform specific things, like os.execute, it tries to launch cmd.exe lol)

[Rohansi]

These are not strictly necessary. MoonSharp is only doing this to try and speed things up a bit by dynamically generating code to access class members instead of using reflection all the time.

I'd try and do without it for now and measure how well plain reflection works. If the performance is very limiting we can look into adding some reflection helpers to generate these kinds of delegates.

[Manonox]

So I guess I should probably just remove the optimization stuff for now

if (m_OptimizedGetter != null)
	result = m_OptimizedGetter(obj);
else
	result = FieldInfo.GetValue(obj); // leave only this

If I find anything that actually requires Expressions, I'll make sure to post it here, thanks