Parameter filters not invoked in Minimal API when using WithOpenApi extension method

[marcominerva]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I'm using .NET 7.0. Following the workaround suggested here: #39886 (comment), I have created the following ParameterFilter to correcly handle Guid constraint:

builder.Services.AddSwaggerGen(options =>
{
    options.ParameterFilter<GuidParameterFilter>();
});

// ...

app.MapGet("api/minimalsample", (Guid id) => TypedResults.NoContent());

// ...

public class GuidParameterFilter : IParameterFilter
{
    public void Apply(OpenApiParameter parameter, ParameterFilterContext context)
    {
        if (context.PropertyInfo is null && parameter.Schema.Type == "string"
            && (context.ApiParameterDescription.Type == typeof(Guid) || context.ApiParameterDescription.Type == typeof(Guid?)))
        {
            parameter.Schema.Format = "uuid";
        }
    }
}

This solves the issue and produce the correct schema for Guid parameter. If, however, I add a call to WithOpenApi extension method after the MapGet, the ParameterFilter is no longer invoked:

app.MapGet("api/minimalsample", (Guid id) => TypedResults.NoContent())
.WithOpenApi();    // This prevent the ParameterFilter to be invoked.

Expected Behavior

Parameter filters should be invoked even when using the WithOpenApi extension method.

Steps To Reproduce

Minimal repro here: https://github.com/marcominerva/ParameterFilterIssue

Exceptions (if any)

No response

.NET Version

7.0.100

Anything else?

Visual Studio 2022 17.4.1

.NET SDK:
Version: 7.0.100
Commit: e12b7af219

Ambiente di runtime:
OS Name: Windows
OS Version: 10.0.22621
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\7.0.100\

Host:
Version: 7.0.0
Architecture: x64
Commit: d099f075e4

.NET SDKs installed:
7.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.31 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.31 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.31 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

[captainsafia]

So, the WithOpenApi extension method works by generating an OpenAPI operation and storing it in metadata. Swashbuckle will favor that OpenApiOperation over the one it generates by default (see here) but do some merging to generate the schemas itself. The ParameterFilters do not get invoked at this level. @marcominerva You might be able to leverage an OperationFilter for this and add another layer of nesting to your invocations.

Resolving domaindrivendev/Swashbuckle.AspNetCore#2521 should help with this in the future.

[marcominerva]

Thank you @captainsafia, using an OperationFilter is a good workaround.

[captainsafia]

@marcominerva Great! I'll file an issue on Swashbuckle to see what it would take to make sure that parameter filters are applied for these types of operations as well. I believe that RequestBodyFilters might also suffer from this issue given my understanding of Swashbuckle's filtering implementation.

See domaindrivendev/Swashbuckle.AspNetCore#2561.