Adding routes using UseEndpoints and WebApplication duplicates route data sources added in UseEndpoints

[davidfowl]

Describe the bug

Adding routes top level and via UseEndpoints duplicated the routes globally. This is because the WebApplicationBuilder internally calls UseEndpoints which results in the datasource being copied twice. This may have performance implications on any code that looks at EndPointDataSource to perform actions (like link generation).

To Reproduce

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.UseRouting();

app.MapGet("/", () => "Hello World!");

app.UseEndpoints(routes =>
{
    routes.MapGet("/hi", () => "Hi World");
    routes.MapGet("/heyo", () => "Heyo World");
});

app.Start();

var ds = app.Services.GetRequiredService<EndpointDataSource>();
foreach (var e in ds.Endpoints)
{
    Console.WriteLine(e.DisplayName);
}

app.WaitForShutdown();

The following prints out:

/hi HTTP: GET
/heyo HTTP: GET
/hi HTTP: GET
/heyo HTTP: GET
/ HTTP: GET

Further technical details

• ASP.NET Core version: Microsoft.AspNetCore.App 6.0.0-rc.1.21406.15

cc @javiercn