Running into a ParseException in a WebGL build

[ReginaldBull]

1. Description

I'm using the library in a Untiy3D project. The project is build for WebGL. Running the application encounters an error as soon the execution comes to parse an expression. Inside the Unity-Editor the execution is running smoothly without any problems.

The expression itself is executing on a list of objects and returns an element where a predicate is met.

2. Exception

ParseException: No applicable aggregate method 'FirstOrDefault(Boolean)' exists
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseEnumerable (System.Linq.Expressions.Expression instance, System.Type elementType, System.String methodName, System.Int32 errorPos, System.Type type) [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseMemberAccess (System.Type type, System.Linq.Expressions.Expression expression) [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParsePrimary () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseUnary () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseArithmetic () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseAdditive () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseShiftOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseComparisonOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseLogicalAndOrOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseIn () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseAndOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseOrOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseLambdaOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseNullCoalescingOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseConditionalOperator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Dynamic.Core.Parser.ExpressionParser.Parse (System.Type resultType, System.Boolean createParameterCtor) [0x00000] in <00000000000000000000000000000000>:0 

I'm passing my classes as custom types to the parser.

Type[] customType=....;
ParameterExpression[] parameterExpressions=....;

_parser.Parse<T>(rule.Expression, parameterExpressions, customTypes)

I will be happy giving more information if needed.

[StefH]

@ReginaldBull Please provide a full working example dotnetfiddle

[ReginaldBull]

I don't know how to provide a fiddle example for a problem that exists within a WebGL (wasm) compiled project.

[StefH]

Can you provide the part from your own code (including the entities / dtos) and the Dynamic LINQ Expression you are trying to parse?

[ReginaldBull]

Basically it all boils down to this:

public class CustomTypeProvider : DefaultDynamicLinqCustomTypeProvider
{
    private readonly HashSet<Type> _types;

    public CustomTypeProvider(Type[] types)
    {
        _types = new HashSet<Type>(types ?? new Type[]
        {
        })
        {
            typeof(Choice),
            typeof(ProductConfiguration),
            typeof(IEnumerable<>)
        };
    }

    public override HashSet<Type> GetCustomTypes() => _types;
}

public class ProductConfiguration{
    public string Code {get; private set;}
    public IEnumerable<IChoice> Choices {get; private set;}=new List<IChoice>();
}

public interface IChoice {
    string Reference{get}
}

public class Choice : IChoice{
    public string Reference {get; private set;}
}

string expression = "input.Choices.FirstOrDefault(p => p.Reference == \"MyReference\")";

Type[] customTypes = new []{
    typeof(Choice),
    typeof(ProductConfiguration),
    typeof(IEnumerable<>)
};

ParameterExpression[] parameterExpressions = new []{
    Expression.Parameter(typeof(ProductConfiguration), "input")
};

ParsingConfig config = new ParsingConfig
{
    CustomTypeProvider = new CustomTypeProvider(customTypes),
    IsCaseSensitive = false
};

EpxressionParser parser = new ExpressionParser(parameterExpressions, expression, new object[]{}, config);

Expression exp = parser.Parse<Choice>(expression, parameterExpression, customTypes);

ProductConfiguration productConfiguration = CreateValidProductConfiguration();

object[] input = new object[]{
    productConfiguration
};

var result = exp(input);

As mentioned, running it locally it works. The problem shows up when using that approach inside a Unity3D WebGL build.

[StefH]

Can you make a simple and small Unity3D WebGL example project ?

[ReginaldBull]

I created a minimal project for reproduction:

https://github.com/ReginaldBull/LinqDynamicCoreUnity3D

[StefH]

@ReginaldBull Thanks for the project, however this is still a very big project. Can you please make a very easy and simple test project please?

[ReginaldBull]

Hello, I removed some unnecessary folders. But this is quite a small project. The source in question can be found under the folder Assets/Scripts.

[StefH]

@ReginaldBull Sorry, I cannot open this project, I do not have all dependencies installed on my system.

Can you maybe use the extension method instead of directly using new ExpressionParser?

And try to write the query you want to execute first as normal LINQ query, and from that, create a the dynamic.

Example:

using System.Linq.Dynamic.Core;
using ConsoleApp1;

string expression = "Choices.FirstOrDefault(p => p.Reference == \"MyReference\")";

Type[] customTypes = new[]
{
    typeof(Choice),
    typeof(ProductConfiguration),
    typeof(IEnumerable<>)
};

var config = new ParsingConfig
{
    CustomTypeProvider = new CustomTypeProvider(customTypes),
    IsCaseSensitive = false
};

var productConfiguration = new ProductConfiguration("code");
var input = new[]
{
    productConfiguration
};

var result = input.Select(i => i.Choices.FirstOrDefault(c => c.Reference == "MyReference")).ToArray();

var resultQ = input.AsQueryable().Select(config, expression).ToDynamicArray();

[ReginaldBull]

Thank you.

Today I tried with the extension method. Running it in Unity Editor mode is working fine but as soon as the web assembly is generated it produces the same error described at the start of this issue.

[ReginaldBull]

One additional finding. I tried again and debugged a bit in deep and found this exception occuring: System.IO.FileNotFoundException: Could not load the file 'System.Private.Corelib'.

System.IO.FileNotFoundException: Could not load the file 'System.Private.Corelib'. File name: 'System.Private.Corelib' at System.AppDomain.Load (System.Reflection.AssemblyName assemblyRef, System.Security.Policy.Evidence assemblySecurity) [0x0007a] in <35594092a38441a79b40e2237d5e8762>:0 at (wrapper remoting-invoke-with-check) System.AppDomain.Load(System.Reflection.AssemblyName,System.Security.Policy.Evidence) at System.AppDomain.Load (System.Reflection.AssemblyName assemblyRef) [0x00000] in <35594092a38441a79b40e2237d5e8762>:0 at (wrapper remoting-invoke-with-check) System.AppDomain.Load(System.Reflection.AssemblyName) at System.Reflection.Assembly.Load (System.Reflection.AssemblyName assemblyRef) [0x00005] in <35594092a38441a79b40e2237d5e8762>:0 at System.Linq.Dynamic.Core.Parser.EnumerationsFromMscorlib.AddEnumsFromAssembly (System.String assemblyName) [0x00006] in <4cc38c5670114affad31d8b74c3f62b1>:0

[StefH]

@ReginaldBull Maybe related to?

• https://github.com/zzzprojects/System.Linq.Dynamic.Core/issues/678
• https://dynamic-linq.net/advanced-blazor-webassembly