Set `Type` in the `ErrorModel`

[victoraugustolls]

Right now, I see no way to directly set the Type of the error as the interface StatusError doesn't include a method, and huma.NewError also doesn't accept a type parameter! Maybe there is something obvious that I'm missing, but right now, I'm passing a custom error type to NewError just to set this field!

@danielgtaylor WDYT of maybe creating a NewErrorWithType or adding a method for StatusError to set the type?

[danielgtaylor]

@victoraugustolls I don't understand, maybe a code example of what you are trying to do would help? You should be able to just create a huma.ErrorModel instance with whatever Type field value you want and return it as the error. You can create your own NewErrorWithType to wrap it all up in your own codebase as needed.

huma.NewError is just a convenience function and it deals with a generic "error with HTTP status" concept. Those errors don't have to be RFC9457 and won't necessarily have a Type field.

[victoraugustolls]

I understand that the errors don't need to be RFC9457! But if it is, the NewError does not provide a parameter to inform the type. What I'm doing right now is:

type ErrorModel struct {
	huma.ErrorModel
}

func (e *ErrorModel) ContentType(ct string) string {
	if ct == "application/json" {
		return "application/json"
	}
	return ct
}

type TypeErr string

func (e TypeErr) Error() string {
	return string(e)
}

var NewErrorWithType = func(status int, msg string, errs ...error) huma.StatusError {
	var details []*huma.ErrorDetail

	var (
		tp      string
		typeErr TypeErr
	)
	for i := 0; i < len(errs); i++ {
		if errs[i] == nil {
			continue
		}

		if converted, ok := errs[i].(huma.ErrorDetailer); ok {
			details = append(details, converted.ErrorDetail())
		} else if errors.As(errs[i], &typeErr) {
			tp = typeErr.Error()
		} else {
			details = append(details, &huma.ErrorDetail{Message: errs[i].Error()})
		}
	}
	return &ErrorModel{
		huma.ErrorModel{
			Type:   tp,
			Status: status,
			Title:  http.StatusText(status),
			Detail: msg,
			Errors: details,
		},
	}
}

[victoraugustolls]

If that is the expected behavior, that's ok! But I feel huma should provide a way to set the type because it exists by default.

[danielgtaylor]

@victoraugustolls how do you use your TypeErr struct? It looks like you might not need a huma.NewErrorWithType as it has the same signature as huma.NewError - am I reading this right that you are just seeing if you can extract some type info from the existing error that is passed in?

[victoraugustolls]

@danielgtaylor exactly! And don't pass the error to the details, only to the type. I'm simulating a type parameter in this case. As an example:

huma.Error403Forbidden("invalid action for token", TypeErr("srn:error:unauthorized"), err)

I wrapped the huma.ErrorModel because I wanted to change the default content type for it!

[danielgtaylor]

@victoraugustolls I do wonder if we are overcomplicating this. Compare it to:

err := huma.Error403Forbidden("invalid action for token", err)
err.Type = "srn:error:unauthorized"

This way you can also set the Instance field and others as needed without any "magic" behind the scenes. If it becomes repetitive you wrap it in a simple utility function. What do you think?

[victoraugustolls]

@danielgtaylor, but huma.Error403Forbidden returns an interface, not the type!

type StatusError interface {
	GetStatus() int
	Error() string
}

I do prefer to be able to set it up directly, as you proposed! It's way simpler.

[victoraugustolls]

Also, the only reason that I am wrapping the huma.ErrorModel is to change the default content type. Is there an easier way to do this? I tried some solutions that worked but seemed the best so far.

[danielgtaylor]

@victoraugustolls yeah you would have to cast, which is a bit annoying to be honest, I guess like:

err := huma.Error403Forbidden("invalid action for token", err).(*huma.ErrorModel)
err.Type = "srn:error:unauthorized"

Alternatively you can write your own utility functions for the different error responses.

Also, the only reason that I am wrapping the huma.ErrorModel is to change the default content type. Is there an easier way to do this?

No, this looks like a reasonable way to do it. 👍

[victoraugustolls]

@danielgtaylor do you feel like there should be an easier way to do both of this operations? If so, I can try of think of something non breaking and suggest it here.

[danielgtaylor]

Moving this to a discussion until we can think up some ways to make it work. In the meantime the easiest solution is probably just to create your own utility methods that behave like huma.Error* but set all the fields you want.