ProblemDetails: make httpstatuses problem types optional about middleware

[sliekens]

Here's how I use it:

options.MapStatusCode = statusCode => new StatusCodeProblemDetails(statusCode)
{
    Type = "about:blank"
};

or

options.MapStatusCode = statusCode => new StatusCodeProblemDetails(statusCode)
{
    Type = null // not recommended if JsonSerializerSettings.NullValueHandling is "Include"
};

[khellang]

So my recommendation is to just leave off the problem type and let it default to about:blank for generic errors. At least make it configurable using ProblemDetailsOptions.

I just included the httpstatuses.com links because I saw that https://github.com/zendframework/zend-problem-details uses them. The upcoming MVC feature uses RFC7231 links as the type. I'm not sure if there's any right or wrong answer here. IMO it's better to go for something that you can dereference to find out more, rather than just about:blank, but we could definitely make this configurable.

[sliekens]

Okay then I think it's fine to leave httpstatuses.com as the default problem type, but make it configurable so I can override it.

Here's what I imagine that would look like:

app.UseProblemDetails(x =>
{
    // This is the default behavior; only include exception details in a development environment.
    x.IncludeExceptionDetails = ctx => Environment.IsDevelopment();

    // This will map NotImplementedException to the 501 Not Implemented status code.
    x.Map<NotImplementedException>(ex => new ExceptionProblemDetails(ex, StatusCodes.Status501NotImplemented));

    // NEW: This will map status code results to problem details
    // **unless** the status code is the product of Map<T, ExceptionProblemDetails>
    x.MapStatusCode(statusCode => new ProblemDetails
    {
        Type = "about:blank",
        Status = statusCode,
        Title = ReasonPhrases.GetReasonPhrase(statusCode)
    });
});

[khellang]

Alright, I pushed v1.2.0 which adds a new property MapStatusCode to ProblemDetailsOptions. It's basically just a Func<int, ProblemDetails> that allows you to map a status code to a problem response.

[sliekens]

Perfect, thanks.