Can't use System.Text.Json or resolve types from Microsoft.Bcl.AsyncInterfaces

[jeremiethibeault]

I'm trying to use System.Text.Json in a WASM project, but I have the following error at runtime.

Could not load signature of System.Text.Json.Serialization.JsonConverter`1[T]:Write due to: Could not load file or assembly 'Microsoft.Bcl.AsyncInterfaces, Version=1.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies.

It appears that System.Text.Json has a dependency to Microsoft.Bcl.AsyncInterfaces.

If I add an explicit reference to Microsoft.Bcl.AsyncInterfaces and try to resolve any of its types (e.g. IAsyncDisposable) , the WASM app stops working the moment I resolve the type.

Steps to reproduce the issue:

1. Add a reference to Microsoft.Bcl.AsyncInterfaces.

<PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="1.0.0" />

2. In the Main method of Program.cs of Uno.Wasm.Sample, have the following code.

static void Main(string[] args)  
{
    Console.WriteLine($"Mono Runtime Mode: " + Environment.GetEnvironmentVariable("UNO_BOOTSTRAP_MONO_RUNTIME_MODE"));

    var i = 42; 
    var now = DateTime.Now.ToString();
    Console.WriteLine($"Main! {i} {now}");

    try
    {
        Console.WriteLine("Getting type from Microsoft.Bcl.AsyncInterfaces");
        var t = typeof(IAsyncDisposable);
        Console.WriteLine("Success!");
    }
    catch (Exception e)
    {
        Console.WriteLine("Something went wrong!" + e.Message);
    }
}

3. Run the app and observe that in the console you get "Getting type from Microsoft.Bcl.AsyncInterfaces" but not "Success!" nor the "Something went wrong" message. There is no error in the output, it simply breaks.