Minimal apis don't show up if GetSwaggerAsyc is called too early

[hahn-kev]

Swashbuckle version 6.4 and 6.5 (didn't test others).

1. Generate a new minimal api project
2. add await app.Services.GetRequiredService<IAsyncSwaggerProvider>().GetSwaggerAsync("v1"); just before app.Run() in program.cs
3. Weather api does not show up in swagger

now the default weather api doesn't show up in swagger. Here's a full copy of the source:

using Swashbuckle.AspNetCore.Swagger;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

var summaries = new[]
{
    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
};
app.UseRouting();
app.MapGet("/weatherforecast",
        () =>
        {
            var forecast = Enumerable.Range(1, 5).Select(index =>
                    new WeatherForecast(
                        DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
                        Random.Shared.Next(-20, 55),
                        summaries[Random.Shared.Next(summaries.Length)]
                    ))
                .ToArray();
            return forecast;
        })
    .WithName("GetWeatherForecast")
    .WithOpenApi();
await app.Services.GetRequiredService<IAsyncSwaggerProvider>().GetSwaggerAsync("v1");
app.Run();

public record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
{
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}

it seems like there's a race condition with calling GetSwaggerAsync too early where the minimal apis don't show up. MVC Controllers will show up correctly. The reason I'm doing this is to validate that we can generate a swagger doc on startup when devs are working. In my case I put it in a service and called generate after a 5 second delay to work around the issue.

[martincostello]

The reason I'm doing this is to validate that we can generate a swagger doc

If it were me, I'd use an integration test to validate this.

I wonder if the endpoints are lazily initialized on first use (or after Run()), so we can't "see" them yet.