Minimal API with RequestDelegateGenerator: Nullable warnings generated when [AsParameters] + [FromBody] are used

[mm-yjn]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Compiler warnings are generated if I use a record as the parameter of the route handler. The record has [AsParameters] annotated in the route parameter, and it contains a constructor parameter with [FromBody].

The warnings are generated from GeneratedRouteBuilderExtensions.g.cs.

Expected Behavior

No warnings should be generated since the framework does not allow null as the request body anyway.

Steps To Reproduce

Create a project with dotnet new webapiaot. Replace the Program.cs with the following code:

using Microsoft.AspNetCore.Mvc;
using System.Text.Json.Serialization;

var builder = WebApplication.CreateSlimBuilder(args);

builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default);
});

var app = builder.Build();

app.MapPost("/test", ([AsParameters] TestClass test) => Results.Ok(test.TestBody));

app.Run();

[JsonSerializable(typeof(string))]
internal partial class AppJsonSerializerContext : JsonSerializerContext;

record TestClass([FromBody] string TestBody);

Exceptions (if any)

1>C:\Users\yjn\source\repos\WebApplication3\WebApplication3\obj\Debug\net10.0\Microsoft.AspNetCore.Http.RequestDelegateGenerator\Microsoft.AspNetCore.Http.RequestDelegateGenerator.RequestDelegateGenerator\GeneratedRouteBuilderExtensions.g.cs(119,60,119,74): warning CS8604: Possible null reference argument for parameter 'TestBody' in 'TestClass.TestClass(string TestBody)'.
1>C:\Users\yjn\source\repos\WebApplication3\WebApplication3\obj\Debug\net10.0\Microsoft.AspNetCore.Http.RequestDelegateGenerator\Microsoft.AspNetCore.Http.RequestDelegateGenerator.RequestDelegateGenerator\GeneratedRouteBuilderExtensions.g.cs(146,60,146,74): warning CS8604: Possible null reference argument for parameter 'TestBody' in 'TestClass.TestClass(string TestBody)'.

.NET Version

10.0.100-rc.1.25451.107

Anything else?

There is a workaround to disable the nullable warnings for this parameter but it looks really ugly.

record TestClass(
#nullable disable
    [FromBody] string TestBody
#nullable restore
    );