When endpoint return ValidationProblem and has errors the property errors doesn't have values.

[jvsancho80]

Is there an existing issue for this?

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Describe the bug

When endpoint return ValidationProblem and has errors the property errors doesn't have values in .Net 8 the same code works ok. I believe return TypedResults.Problem instead of TypedResults.ValidationProblem. My code return TypedResults.ValidationProblem. I have checked it and my code is correct.

Net 8

Net 9

My code works in Net 8

Expected Behavior

The code return this because my code return TypedResults.ValidationProblems. Net8 the same code works ok.

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

Net 9

Anything else?

No response

[jvsancho80]

When will resolve this issue @martincostello ? I think is an important because is not possible use ValidationProblemDetails.

Thanks

[sguryev]

I have found the source of the issue.
In the NET8 we didn't have IProblemDetailsService usage in the ValidationProblem.ExecuteAsync() method. So it was writing HttpValidationProblemDetails object to the JSON.

In the NET9 we have a new approach with IProblemDetailsService

aspnetcore/src/Http/Http.Results/src/ValidationProblem.cs

Line 63 in 67ae6c8

if (problemDetailsService is null || !await problemDetailsService.TryWriteAsync(new() { HttpContext = httpContext, ProblemDetails = ProblemDetails }))

The AddProblemDetails() extension method adds DefaultProblemDetailsWriter in addition to the DefaultApiProblemDetailsWriter which is added by AddMvcCoreServices()

In case the wrong order DefaultApiProblemDetailsWriter will be called first by ProblemDetailsService it will handle the problem, create basic ProblemDetails and forget about Errors property from the derived HttpValidationProblemDetails or ValidationProblemDetails

As the result: Errors property is missing.

But placing AddProblemDetails() before AddControllers(), AddMvc(), etc will place the DefaultProblemDetailsWriter before DefaultApiProblemDetailsWriter and it will be used by ProblemDetailsService. DefaultProblemDetailsWriter preserves the original problem details object from the ProblemDetailsContext instead of creating a new one.

I have found one mention about the order here: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/error-handling?view=aspnetcore-9.0#custom-iproblemdetailswriter
But it's related to the custom IProblemDetailsWriter not the AddProblemDetails() call in general.

I'm not sure if current DefaultApiProblemDetailsWriter behavior is correct.
Same guide has a sample with incorrect order of calls which makes me think that DefaultApiProblemDetailsWriter has to be fixed.

[jvsancho80]

Now it works. Thanks

[NKnusperer]

If you are using ASP.NET API Versioning AddProblemDetails() has to be called before AddApiVersioning() too:

1. AddProblemDetails()
2. AddApiVersioning()
3. AddControllers()

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