404 for 'swagger.json' when running in IIS

[rverberne]

In IIS there is a site: localhost:4444
This site has multiple applications, one ASP.Net core, with Kestrel, not in process. Application has name webapp.

Swagger UI is visible at localhost:4444/webapp/swagger/index.html.
Now from browser request is made to localhost:4444/swagger/v1/swagger.json and gives 404.
Other files (CSS, javascript, favicon) all work.

Is this a bug? I am trying to fix it with TransformToExternalPath lambda.

[rverberne]

Fix:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
	app.UseSwaggerUi3(config =>
	{
		config.TransformToExternalPath = (s, r) =>
		{
			string path = s.EndsWith("swagger.json") && !string.IsNullOrEmpty(r.PathBase)
				? $"{r.PathBase}{s}"
				: s;
			return path;
		};
		config.TagsSorter = "alpha";
		config.OperationsSorter = "alpha";
		config.EnableTryItOut = false;
	});
}

But should this be necessary?