[Minimal API] IFormFile does not bind 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 7.0.4. I have defined the following endpoints:

app.MapPost("/api/upload", (IFormFile file) =>
{
    return TypedResults.Ok(file.FileName);
});

app.MapPost("/api/upload_with_openapi", (IFormFile file) =>
{
    return TypedResults.Ok(file.FileName);
})
.WithOpenApi();

When I invoke the first one, everything works as expected. However, when I call the endpoint that uses WithOpenApi, I get an exception:

Microsoft.AspNetCore.Http.BadHttpRequestException: Required parameter "IFormFile file" was not provided from form file.
   at lambda_method3(Closure, Object, HttpContext, Object)
   at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass92_2.<<HandleRequestBodyAndCompileRequestDelegateForForm>b__2>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
   at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

I have also tried adding the [FromForm] attribute to the IFormFile parameter, but with no luck.

Expected Behavior

IFormFile should work even when using the WithOpenApi extension method.

Steps To Reproduce

Minimal repro: https://github.com/marcominerva/FileUploadIssue

Exceptions (if any)

No response

.NET Version

7.0.202

Anything else?

No response

[mitchdenny]

This does look like a bug. Thanks for reporting it!

[captainsafia]

Without the WithOpenApi call, the schema that is produced looks as follows:

schema": {
  "required": [
    "file"
  ],
  "type": "object",
  "properties": {
    "file": {
      "type": "string",
      "format": "binary"
    }
  }
},

With the call invoked, the schema looks as follows:

"schema": {
  "type": "string",
  "format": "binary"
},

Since we still rely on the schema generation logic in Swashbuckle (ref), I suspect the bug is in the fact that we don't invoke the GenerateSchemaFromFormParameters method in the schema override logic.

We'll have to fix this bug over on the Swashbuckle side for now.

@marcominerva Do you mind filing this issue in the Swashbuckle.AspNetCore repo?

[marcominerva]

Sure @captainsafia, done :) Thank you for your support!

[mitchdenny]

Closing this bug here now that there is one tracking it on the Swashbuckle side.