Broken code snippet in documentation (Assertions > Extensibility > Chaining and Converting)

[maximerety]

Description

In https://tunit.dev/docs/assertions/extensibility/extensibility-chaining-and-converting/#1-create-the-assertion-class, the proposed code snippet does not compile:

public class IsProblemDetailsAssertion : Assertion<ProblemDetails>
{
    public IsProblemDetailsAssertion(AssertionContext<HttpResponseMessage> context)
        : base(context.Map<ProblemDetails>(async response =>
        {
            var content = await response.Content.ReadFromJsonAsync<ProblemDetails>();

            if (content is null)
            {
                throw new InvalidOperationException("Response body is not Problem Details");
            }

            return content;
        }))
    {
    }

    // [skipped]
}

This snippet would require an overload of the AssertionContext's Map method with the following signature, which does not exist:

public AssertionContext<TNew?> Map<TNew>(Func<TValue?, Task<TNew?>> mapper)

Discussion

We do have the following MapAsync method which is pretty close, but it changes the source value type to Task<TNew?> which is not desired:

public AssertionContext<Task<TNew?>> MapAsync<TNew>(Func<TValue?, Task<TNew?>> mapper)

A possible (although ugly) workaround is to force running async code synchronously:

public class IsProblemDetailsAssertion : Assertion<ProblemDetails>
{
    public IsProblemDetailsAssertion(AssertionContext<HttpResponseMessage> context)
        : base(context.Map(response =>
        {
            var content = Task.Run(() => response?.Content.ReadFromJsonAsync<ProblemDetails>()).GetAwaiter().GetResult();

            if (content is null)
            {
                throw new InvalidOperationException("Response body is not Problem Details");
            }

            return content;
        }))
    {
    }
}

Would there be any cleaner way to perform async conversions?