Analyzer: Warn that IResult should not be returned from Controller Actions

[brunolins16]

Today, with the new Microsoft.AspNetCore.Http.Results class is very easy to get confused and implement a Controller Action similar with that, or any other variation of the methods exposed by this class:

[HttpGet]
public IResult Get()
{
    return Results.Ok();
}

Also, is very easy to use an Microsoft.AspNetCore.Http.IResult custom implementation as a return of a controller action, like this:

public class MyCustomResult : IResult
{
    public Task ExecuteAsync(HttpContext httpContext) => Task.CompletedTask;
}

[HttpGet]
public IResult Get()
{
    return new MyCustomResult();
}

Both examples will not throw exception but will serialize the class. For the first example the action will return the following payload:

{
  "value": null,
  "statusCode": 200,
  "contentType": null
}

In rare situations it will be the expected behavior. With that, we should add an analyzer that detects if the action return an Microsoft.AspNetCore.Http.IResult and fail/warn. It might be also possible provide a code fix suggestion in cases where the ControllerBase has a similar method, eg:

From:

[HttpGet]
public IResult Get()
{
    return Results.Ok();
}

To:

[HttpGet]
public IResult Get()
{
    return Ok();
}

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[davidfowl]

Or maybe we should support them?

[brunolins16]

@davidfowl In my opinion, it is very confusing already and will become even more when we start look into #37502. However, this is just my initial thoughts related to #33403 and maybe we support them might be a better option.

[davidfowl]

Yea I see how that can be very problematic from a developer POV. Also unfortunately the controller base class has all of those methods that make it hard to move away from action result and prefer Results.XX. Maybe throwing is a fine way to start.

[brunolins16]

We decided to add the support for IResult types in MVC Action controllers. #40639