Razor Component IResult

[SteveSandersonMS]

Implements #46990

There's a lot of new public API here but it's almost all boilerplate stuff following the exact patterns of PageResult, PageResultExecutor, etc.

I'm looking for feedback from MVC/Razor Pages/MinimalAPI folks on whether this is the right approach. In particular, I made RazorComponentResult be a plain IResult, not an IActionResult or even a ViewResult because we want this to work in minimal APIs, and have no requirement for MVC-like action/view concepts. If there's some reason why it should be a ViewResult, say, please let me know. @halter73 - do you have a recommendation?

[javiercn]

Don't we expect to have methods con Controller and Page to render a component?

[javiercn]

Is this meant to be an anonymously initialized object? (new { A = 1, B = 'c' })

[SteveSandersonMS]

It's like what we support with Html.RenderComponentAsync - it can be an anonymously-typed object, or an IDictionary<string, object>. We could add explicit support for it being a ParameterView but I don't think many people would want to be constructing one of those.

[javiercn]

How do you unit test this action result? Not the output, but the result of a controller action that returns this result.

[SteveSandersonMS]

I'm probably not following the question, but I expected it to be the same as with any other controller action. You would have to declare the action return type as RazorComponentResult and then your unit test could inspect its properties. Or you could downcast to RazorComponentResult in the unit test. If you mean something else please clarify 😄

[javiercn]

Ok, I guess that I am trying to get at is that we should probably make this a ParameterView instance and do the conversion/cast from object to it on the constructor. Otherwise, it's really hard to do anything with the parameters other than treat them as an opaque blob

[SteveSandersonMS]

OK, I see. TBH a ParameterView isn't much easier to write assertions about - it doesn't give you random access unless you convert it to a Dictionary<string, object>

We could expose the result of PropertyHelper.ObjectToDictionary(yourValue) since we're going to perform that conversion later in order to build a ParameterView.

[javiercn]

We can make it a Dictionary<string, object>, that will work, even if we then convert it to a ParameterView later on

[SteveSandersonMS]

Yep, that's what I mean with "expose the result of PropertyHelper.ObjectToDictionary(yourValue)".

Following this suggestion I've changed it and added unit tests showing how you can read the parameter values from the dictionary.

[SteveSandersonMS]

Don't we expect to have methods con Controller and Page to render a component?

I'm totally fine with adding that but was hoping for feedback from some of the MVC-type people. At least in the MVC controller sense it makes sense to me, maybe a bit less so for a Razor page.

As it stands, it's already easy to use from an MVC controller because you just do:

public class HomeController : Controller
{
    public IResult MyAction()
        => new RazorComponentResult<MyPageComponent>();
}

Whether there's any clear merit to also adding a helper method on Controller I don't know. The usage experience would be very similar:

public class HomeController : Controller
{
    public IResult MyAction()
        => RazorComponent<MyPageComponent>();
}

[javiercn]

@SteveSandersonMS I think we should have at least a method on Controller to do render it, I do not believe we have any action result that we tell users to instantiate manually.

[SteveSandersonMS]

What about for Minimal APIs? Are minimal people OK with instantiating their own result objects? If not I think I need to put this in the Microsoft.AspNetCore.Http.Results project, which is awkward because then I have to make that reference Mvc.ViewFeatures, or we have to do some bigger refactoring. I don't think we should hang it off Results.Extensions - that would be super weird for a built-in feature. cc @captainsafia

[SteveSandersonMS]

@javiercn Adding the helpers for constructing a RazorComponentResult is the sort of detail we talked about that can be filled in later. Since we don't yet have any feedback from Minimal/MVC people here, I've filed #47094 and suggest we proceed with the more basic low-level APIs in this PR for now.

[javiercn]

Since we have changed this to only implement IResult and not IActionResult, does it run through the MVC result filters?

[SteveSandersonMS]

Yes, MVC runs result filters around IResult results.

[javiercn]

Looks great, I am not 100% sure how I feel about automatically rendering the Layout for a component, or if there should be a way to override that choice.

I believe MVC has functionality to change the layout or signal that you don't want the layout, maybe we should consider having similar functionality.

[SteveSandersonMS]

Adding the ability to override the layout would be fine and easy for us to add later. Strictly speaking there are other ways to do this anyway, but if enough people want it then we could make it more convenient.