Limited exception information ... stuck ...

[TehWardy]

Hey guys,

I got everything running under .Net 4.x and then it turned out for M$ reasons the only way everything was going to work the way I wanted was to upgrade to .Net Core 2.2 so here I am.

This code works perfectly under .Net 4.x but for some reason under .Net Core I can't seem to get it to behave and the exception is giving me literally nothing.

So here's the code ....

var script = "((Core.Objects.Workflow.Activities.DebugActivity)activity).Message = ((Core.Objects.Workflow.Activities.Start<System.Object>)activity.Previous[0]).Data.Message;";
var result = assignContext.Compile<Action<Activity>>(script, "activity");

At runtime I have a collection of Activities that derive from this base type ...

   public abstract class Activity
    {
        public string Ref { get; set; }
        public Activity[] Previous { get; set; }
        public Activity[] Next { get; set; }
        public Action<Activity> AssignValues { get; set; } 
        ....
    }

... I have a "Flow" object that contains a collection of activities and a collection of "Links" which contain the expressions that I need to compile.

After constructing each activity as it's concrete type and assigning each of the previous and next arrays shown in the base type above I run the code that's failing in an attempt to build the AssignValues Action for each activity that has link information.

The exception information I'm getting looks like this ...

Message

Value cannot be null.

Stack trace

   at System.RuntimeType.MakeGenericType(Type[] instantiation)
   at .(ExpressionScope , SyntaxNode , StringBuilder , Int32& , Boolean )
   at .(ExpressionScope , SyntaxNode , StringBuilder , Int32& , Boolean )
   at .(ExpressionScope , SyntaxNode , Boolean )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at .(ExpressionScope , SyntaxNode )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at .(ExpressionScope , SyntaxNode , Expression , Boolean )
   at Z.Expressions.CodeCompiler.CSharp.ExpressionParser.ParseSyntax(ExpressionScope scope, SyntaxNode node, Type resultType)
   at .[](EvalContext , String , IDictionary`2 , Type , EvalCompilerParameterKind , Boolean , Boolean )
   at Z.Expressions.EvalContext.Compile[TDelegate](String code, String[] parameterNames)
   at Workflow.FlowInstance.BuildAssign[T](T activity, Flow flow) in D:\Core Prototype\Everything\Workflow\FlowInstance.cs:line 247

Is there any obvious reason that this would fail as this seems pretty straightforward for the code I have?

[TehWardy]

Oh one other thing ... this is how I setup the "assignContext" which is a ZZZ EvalContext that i'm using for this call ...

// some of the stack might not have been loaded, lets make sure we load everything so we can give a complete response
// first grab what's loaded
var loadedAlready = AppDomain.CurrentDomain
        .GetAssemblies()
        .Where(a => a.FullName.StartsWith("Core"))
        .ToList();

// then grab the bin directory
var binDir = Assembly.GetExecutingAssembly().CodeBase
    .Replace(Assembly.GetExecutingAssembly().CodeBase.Split('/').Last(), "")
    .Replace("file:///", "")
    .Replace("/", "\\");

// from the bin, grab our core dll files
var stackDlls = Directory.GetFiles(binDir)
    .Select(i => i.ToLowerInvariant())
    .Where(f => f.EndsWith("dll") && f.Split('\\').Last().StartsWith("core"))
    .ToList();

// load the missing ones
foreach (var assemblyPath in stackDlls)
    if (loadedAlready.All(a => a.CodeBase.ToLowerInvariant() != assemblyPath))
        loadedAlready.Add(Assembly.LoadFile(assemblyPath));

// now everything is loaded, lets not do this again
stackAssemblies = loadedAlready.Distinct(new AssemblyComparer()).ToArray();

assignContext = new EvalContext { IncludeMemberFromAllParameters = false };
assignContext.RegisterAssembly(stackAssemblies);

... all the types I care about are in assemblies named "Core.*.dll" so this is a targeted fetch that pulls all the things it could possibly need.

[JonathanMagnan]

Thank you @TehWardy for reporting,

We have not been able to reproduce it but we might have missed something.

Do you think you could provide a standalone version with only this code that fails?

[TehWardy]

New project > net core console app, then drop this in ...

using System;
using Z.Expressions;

namespace ExpressionThing
{
    class Program
    {
        static void Main(string[] args)
        {
            var script = "((ExpressionThing.DebugActivity)activity).Message = ((ExpressionThing.Start<System.Object>)activity.Previous[0]).Data.Message;";
            var ctx = new EvalContext { IncludeMemberFromAllParameters = false };

            var victim = new DebugActivity {
                // Assigned by unrelated code to a collection of stuff that inherits Activity.
                Previous = null, 
                Next = null,

                // The problem code
                AssignValues = ctx.Compile<Action<Activity>>(script, "activity")
            };

            Console.ReadKey();
        }
    }

    public class DebugActivity : Activity
    {
        public string Message { get; set; }
    }

    public class Start<T> : Activity
    {
        public T Data { get; set; }
    }

    public abstract class Activity
    {
        public string Ref { get; set; }
        public Activity[] Previous { get; set; }
        public Activity[] Next { get; set; }
        public Action<Activity> AssignValues { get; set; }

    }
}
}

My understanding is that this should work as i'm only trying to compile the function at this time and not actually run it.

[TehWardy]

@JonathanMagnan random question ...
Do you have a discord server?

I use discord a lot and we have a discord server for the company, it's real easy to share code samples and discuss problems on.

[JonathanMagnan]

Thank you,

We are currently looking at it.

[JonathanMagnan]

Hello @TehWardy ,

You do not register class in your project which causes the issue.

Here is a way to do it by registering a namespace:

ctx.RegisterNamespace(typeof(Program).Assembly, "ExpressionThing");

[TehWardy]

Oh ... that's new ... I didn't have to do that before under .Net 4 ... is this a .Net Core thing?

[TehWardy]

Given my original example source the last line of code had ...

assignContext.RegisterAssembly(stackAssemblies);

.... Is it possible to have an override of this that auto registers all namespaces in the given assmeblies?

[JonathanMagnan]

Hello @TehWardy ,

No, that's not new to .NET Core. You had to do it also before.

Is it possible to have an override of this that auto registers all namespaces in the given assmeblies?

I'm not sure to understand what exactly you want. You just need to call the RegisterAssembly. If you have a class that inherit from our context, you can add this code in your constructor.

[TehWardy]

My understanding is that if I do this ...

var ctx = new EvalContext { IncludeMemberFromAllParameters = false };
ctx.RegisterAssembly(stackAssemblies);

I'm constructing the context then telling it what types I want it to know about as a collection of assemblies that contain them.

What I think you're saying is that In addition to providing the assemblies I also need to tell it what namespaces from those assemblies I want to use.
What I guess i'm asking is "Given either a collection of assemblies or defaulting to the current AppDomain can the context simply know about all types in all namespaces".

What's the purpose of the RegisterNamespace call beyond what I would hope is default behaviour based on what I have described?

[JonathanMagnan]

What I think you're saying is that In addition to providing the assemblies I also need to tell it what namespaces from those assemblies I want to use.

Not at all,

The RegisterAssembly(stackAssemblies); works great. Our library will register all types in all namespaces which is exactly what you want.

You do not have to use the RegisterNamespace, it is just another way to register type in our library.

[TehWardy]

Oh i see what you're saying ... yeh my bad ...
That means the sample I gave you is broken in a different way to the code in my main code base but exhibits the same exception behaviour so the exception could be related / similar to the actual problem I have.

Having checked in my code and the expression used when I put a breakpoint on the last line in the original question example I find that the assembly collection passed in contains the assembly with both types I'm using in the expression ... do I also need to provide thing's like System or is the framework automatically included?

I'm thinking the smart way to go about this is to simply load all assemblies I care about in to the app domain then just give that last line the full set like this ...

var ctx = new EvalContext { IncludeMemberFromAllParameters = false };
ctx.RegisterAssembly(AppDomain.CurrentDomain.GetAssemblies());

... Would you expect that to behave as expected?
The trouble is that exhibits the same behaviour.

Is there some way to query the context to ask it for a list of types it knows about so I can watch window it and double check that I have everything setup as expected?

[JonathanMagnan]

Hello @TehWardy ,

Just to let you know, my developer started to work on something that will tell you which types are missing.

He almost completed the code so we should be able to provide you something probably on Monday.

[TehWardy]

Awesome :) you guys are on overtime bashing this out on a bank holiday weekend I love the dedication :)