SentryTracingBuilder.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;

namespace Sentry.AspNetCore;

/// <summary>
/// Delegates/wraps the inner builder, so that we can intercept calls to <see cref="Use"/> and add our middleware
/// </summary>
internal class SentryTracingBuilder : IApplicationBuilder
{
    private const string EndpointRouteBuilder = "__EndpointRouteBuilder";
    public SentryTracingBuilder(IApplicationBuilder inner)
    {
        InnerBuilder = inner;
    }

    private IApplicationBuilder InnerBuilder { get; }

    /// <inheritdoc />
    public IServiceProvider ApplicationServices
    {
        get => InnerBuilder.ApplicationServices;
        set => InnerBuilder.ApplicationServices = value;
    }

    /// <inheritdoc />
    public IDictionary<string, object?> Properties => InnerBuilder.Properties;

    /// <inheritdoc />
    public IFeatureCollection ServerFeatures => InnerBuilder.ServerFeatures;

    /// <inheritdoc />
    public RequestDelegate Build() => InnerBuilder.Build();

    /// <inheritdoc />
    public IApplicationBuilder New() => new SentryTracingBuilder(InnerBuilder.New());

    /// <inheritdoc />
    public IApplicationBuilder Use(Func<RequestDelegate, RequestDelegate> middleware)
    {
        // UseRouting sets a property on the builder that we use to detect when UseRouting has been added and we
        // register SentryTracing immediately afterwards
        // https://github.com/dotnet/aspnetcore/blob/8eaf4b51f73ae2b0ed079e4f8253afb53e96b703/src/Http/Routing/src/Builder/EndpointRoutingApplicationBuilderExtensions.cs#L58-L62
        if (Properties.ContainsKey(EndpointRouteBuilder) && this.ShouldRegisterSentryTracing())
        {
            var options = InnerBuilder.ApplicationServices.GetService<IOptions<SentryAspNetCoreOptions>>();
            var instrumenter = options?.Value.Instrumenter ?? Instrumenter.Sentry;
            var autoRegisterTracing = options?.Value.AutoRegisterTracing ?? true;
            if (instrumenter == Instrumenter.Sentry && autoRegisterTracing)
            {
                InnerBuilder.Use(middleware).UseSentryTracingInternal();
                return this; // Make sure we return the same builder (not the inner builder), for chaining
            }
            this.StoreRegistrationDecision(false); // Saves us from having to resolve the options to make this check again
        }

        InnerBuilder.Use(middleware);
        return this; // Make sure we return the same builder (not the inner builder), for chaining
    }
}