AnthonyGiretti

public class AuditMiddleware
{
    private readonly RequestDelegate _next;

    public AuditMiddleware(RequestDelegate next) => _next = next;

    public async Task InvokeAsync(HttpContext context)
    {
        var endpoint = context.GetEndpoint(); // <-- Enables benefit of the middleware improvement
        var requiresAudit = endpoint?.Metadata.GetMetadata<RequiresAuditAttribute>();

AnthonyGiretti

// This attribute encodes the exact position of the call site to intercept:
// file path + line + column, hashed into a compact base64 string
[InterceptsLocationAttribute(1, "qjmcoI/hUdYHdlM5/alrVYsBAABPcmRlclNlcnZpY2UuY3M=")]
internal static void Log_Intercepted_0(string message, LogLevel level)
{
    // Substitute logic — zero-allocation, AOT-friendly, audit trail, etc.
    StructuredLogger.Write(level, message);
}

AnthonyGiretti

// This is what ends up in the compiled IL — invisible to the developer
GeneratedInterceptors.Log_Intercepted_0("Order created", LogLevel.Information);

AnthonyGiretti

// This is what the developer writes
Logger.Log("Order created", LogLevel.Information);

AnthonyGiretti

// <auto-generated/>
#nullable enable
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using MyApi;

namespace System.Runtime.CompilerServices
{
    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]

AnthonyGiretti

private static void Generate(
    SourceProductionContext spc,
    ImmutableArray<InterceptorTarget> targets)
{
    if (targets.IsDefaultOrEmpty) return;

    var sb = new StringBuilder();
    sb.AppendLine("// <auto-generated/>");
    sb.AppendLine("#nullable enable");
    sb.AppendLine("using System.Net.Http;");

AnthonyGiretti

using System.Collections.Immutable;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace CorrelationInterceptors.Generator;

[Generator]
public sealed class HttpClientInterceptorGenerator : IIncrementalGenerator

AnthonyGiretti

namespace MyApi;

public class OrderService(HttpClient httpClient)
{
    public async Task<string> GetOrderAsync(Guid orderId)
    {
        var request = new HttpRequestMessage(
            HttpMethod.Get, $"https://orders-api/orders/{orderId}");

        // No manual header injection — the interceptor handles it at compile time

AnthonyGiretti

namespace MyApi;

public class CorrelationMiddleware(RequestDelegate next)
{
    public async Task InvokeAsync(HttpContext context)
    {
        CorrelationContext.CorrelationId =
            context.Request.Headers["X-Correlation-ID"].FirstOrDefault()
            ?? Guid.NewGuid().ToString();

AnthonyGiretti

namespace MyApi;

public static class CorrelationContext
{
    private static readonly AsyncLocal<string?> _correlationId = new();

    public static string? CorrelationId
    {
        get => _correlationId.Value;
        set => _correlationId.Value = value;