WASM-compilation breaks Microsoft.CodeAnalysis

[VYDocuWare]

Description

Hello. I've created a project, which makes use of Microsoft.CodeAnalysis, and I compile it to WASM using

<RuntimeIdentifier>browser-wasm</RuntimeIdentifier>

However, when I start RoslynWebAssembly/bin/Release/net9.0/browser-wasm/AppBundle/main.js in a browser environment, I get the following error:

Uncaught ManagedError: Argument_EmptyString Arg_ParamName_Name, path at sn (marshal-to-js.ts:420:18) at gn (managed-exports.ts:316:15) at Object.<anonymous> (invoke-cs.ts:321:17) at main.js:12:50

Any help?

Reproduction Steps

Here's a reproduction of the non-working project: https://github.com/VYDocuWare/RoslynWebAssembly

Expected behavior

The wasm-compiled method returns "IsSpeculativeSemanticModel", which is my test of whether the SemanticModel has been generated.

Actual behavior

I get the following error:

Uncaught ManagedError: Argument_EmptyString Arg_ParamName_Name, path at sn (marshal-to-js.ts:420:18) at gn (managed-exports.ts:316:15) at Object.<anonymous> (invoke-cs.ts:321:17) at main.js:12:50

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[maraf]

@VYDocuWare It is an exception raised inside Roslyn codebase. You can wrap your JSExport method with try-catch to get more details

[JSExport]
static bool GetCompiledResult()
{
    try
    {
        var expressionOutcome = ExpressionProcessor.ProcessExpression();
        return expressionOutcome.IsSpeculativeSemanticModel;
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error: {ex}");
        return false;
    }
}

[VYDocuWare]

Thanks. I pushed the try/catch and a simplifying change to the reproduction-repository.

Here's the error I now get:

dotnet.native.js:8 Error: System.ArgumentException: Argument_EmptyString Arg_ParamName_Name, path
dotnet.native.js:8    at System.ArgumentException.ThrowNullOrEmptyException(String , String )
dotnet.native.js:8    at System.ArgumentException.ThrowIfNullOrEmpty(String , String )
dotnet.native.js:8    at System.IO.Strategies.FileStreamHelpers.ValidateArguments(String , FileMode , FileAccess , FileShare , Int32 , FileOptions , Int64 )
dotnet.native.js:8    at System.IO.FileStream..ctor(String , FileMode , FileAccess , FileShare , Int32 , FileOptions , Int64 )
dotnet.native.js:8    at System.IO.FileStream..ctor(String , FileMode , FileAccess , FileShare , Int32 , FileOptions )
dotnet.native.js:8    at System.IO.FileStream..ctor(String , FileMode , FileAccess , FileShare , Int32 , Boolean )
dotnet.native.js:8    at System.IO.FileStream..ctor(String , FileMode , FileAccess , FileShare )
dotnet.native.js:8    at Roslyn.Utilities.StandardFileSystem.OpenFile(String , FileMode , FileAccess , FileShare )
dotnet.native.js:8    at Roslyn.Utilities.CommonCompilerFileSystemExtensions.OpenFileWithNormalizedException(ICommonCompilerFileSystem , String , FileMode , FileAccess , FileShare )
dotnet.native.js:8    at Microsoft.CodeAnalysis.MetadataReference.CreateFromFile(String , MetadataReferenceProperties , DocumentationProvider )
dotnet.native.js:8    at DocuWare.WorkflowDesigner.ExpressionProcessing.ExpressionProcessor.GetProcessingResult()
dotnet.native.js:8    at DocuWare.WorkflowDesigner.ExpressionProcessing.ExpressionProcessor.ProcessExpression()
dotnet.native.js:8    at RoslynWebAssembly.Program.GetCompiledResult()

I see it's due to the below code in ExpressionProcessor.cs:

var compilation = VisualBasicCompilation.Create("TemporaryCompilation",
    syntaxTrees: new[] { tree },
    references: new[]
    {
        MetadataReference.CreateFromFile(typeof(Microsoft.VisualBasic.Constants).Assembly.Location),
        MetadataReference.CreateFromFile(typeof(System.Diagnostics.Debug).Assembly.Location),
        MetadataReference.CreateFromFile(Assembly.Load("System.Runtime, Version=6.0.0.0").Location),
    });

I actually need these references, as I can't validate my code without them. Any help?

[JakeYallop]

.Assembly.Location is empty when running in WASM. To create metadata references, you currently have to redownload the dlls and use CreateFromStream:

https://github.com/JakeYallop/WasmSharp/blob/main/packages/core/src/Services/WasmMetadataReferenceResolver.cs#L24-L31

With #111642, there is probably going to be an easier way to do this in .NET 10.

[VYDocuWare]

Thanks. I now load the .dlls separately, and it seems to work. I pushed the code to the repository. However, from my understanding, this will cause the browser to fetch the .dlls every time there's a validation request.

Is there a way to load the .dlls once, and then reuse them across all the validation requests? That is, can I "store" the .dlls someplace accessible to the validator, and have it check for them?

[VYDocuWare]

Also, I've noticed that the WASM Expression Validator works in the main browser thread, causing it to block when running. Is there a way to make it run in a separate thread, without using web workers myself?

[JakeYallop]

Is there a way to load the .dlls once, and then reuse them across all the validation requests? That is, can I "store" the .dlls someplace accessible to the validator, and have it check for them?

WasmSharp has a global metadata reference cache that it stores all the metadata references in.

Is there a way to make it run in a separate thread, without using web workers myself?

Not that I know of - however it's been a while since I last looked into any of this (including e.g multi-threaded WASM).

[maraf]

Also, I've noticed that the WASM Expression Validator works in the main browser thread, causing it to block when running. Is there a way to make it run in a separate thread, without using web workers myself?

If you set WasmEnableThreads=true in your csproj, you'll get a multi threaded .NET runtime. It's still experimental, but the progress from last year is amazing.

[VYDocuWare]

WasmSharp has a global metadata reference cache that it stores all the metadata references in.

How can I make use of this in my own project?

[JakeYallop]

It's more complicated that it sounds - its just a

static readonly List<MetadataReference> References

With a wrapper class around it.