Address request context review feedback

Author: dustinbyrne

src/PostHog.AspNetCore/Tracing/PostHogRequestContextMiddlewareExtensions.cs

@@ -1,4 +1,6 @@
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Features;
 
 namespace PostHog;
 
@@ -19,11 +21,34 @@ public static IApplicationBuilder UsePostHogRequestContext(
     {
         if (app is null)
         {
-            return app!;
+            return new NoOpApplicationBuilder();
         }
 
         var options = new PostHogRequestContextOptions();
         configure?.Invoke(options);
         return app.UseMiddleware<PostHogRequestContextMiddleware>(options);
     }
+
+    sealed class NoOpApplicationBuilder : IApplicationBuilder
+    {
+        readonly IFeatureCollection _serverFeatures = new FeatureCollection();
+        readonly IDictionary<string, object?> _properties = new Dictionary<string, object?>();
+
+        public IServiceProvider ApplicationServices { get; set; } = new NoOpServiceProvider();
+
+        public IFeatureCollection ServerFeatures => _serverFeatures;
+
+        public IDictionary<string, object?> Properties => _properties;
+
+        public IApplicationBuilder Use(Func<RequestDelegate, RequestDelegate> middleware) => this;
+
+        public IApplicationBuilder New() => new NoOpApplicationBuilder();
+
+        public RequestDelegate Build() => _ => Task.CompletedTask;
+    }
+
+    sealed class NoOpServiceProvider : IServiceProvider
+    {
+        public object? GetService(Type serviceType) => null;
+    }
 }

src/PostHog.AspNetCore/Tracing/PostHogTracingHeaders.cs

@@ -74,8 +74,7 @@ public static PostHogRequestContextData Extract(HttpContext? httpContext, PostHo
             return null;
         }
 
-        var value = values.Count > 0 ? values[0] : values.ToString();
-        return SanitizeValue(value);
+        return SanitizeValue(values[0]);
     }
 
     internal static string? SanitizeValue(string? value)
@@ -117,7 +116,8 @@ static void AddIfPresent(Dictionary<string, object> properties, string key, stri
             "://",
             request.Host.ToUriComponent(),
             request.PathBase.ToUriComponent(),
-            request.Path.ToUriComponent());
+            request.Path.ToUriComponent(),
+            request.QueryString.ToUriComponent());
     }
 
     static string? GetRequestPath(HttpRequest request)

tests/UnitTests.AspNetCore/PostHogRequestContextMiddlewareTests.cs

@@ -20,6 +20,15 @@ public async Task NullHttpContextDoesNotThrow()
         await middleware.InvokeAsync(null);
     }
 
+    [Fact]
+    public async Task NullApplicationBuilderReturnsNoOpBuilder()
+    {
+        var app = PostHogRequestContextMiddlewareExtensions.UsePostHogRequestContext(null!);
+
+        Assert.NotNull(app);
+        await app.Build()(new DefaultHttpContext());
+    }
+
     [Fact]
     public void NullTracingExtractionInputsReturnEmptyContext()
     {
@@ -60,7 +69,7 @@ public async Task AppliesRequestContextHeadersAndRequestMetadataToDownstreamCapt
         Assert.Equal("frontend-user", batchItem.GetProperty("distinct_id").GetString());
         var properties = batchItem.GetProperty("properties");
         Assert.Equal("frontend-session", properties.GetProperty("$session_id").GetString());
-        Assert.Equal("https://example.com/api/test", properties.GetProperty("$current_url").GetString());
+        Assert.Equal("https://example.com/api/test?filter=1", properties.GetProperty("$current_url").GetString());
         Assert.Equal("POST", properties.GetProperty("$request_method").GetString());
         Assert.Equal("/api/test", properties.GetProperty("$request_path").GetString());
         Assert.Equal("TestAgent/1.0", properties.GetProperty("$user_agent").GetString());
@@ -255,7 +264,7 @@ public async Task CapturesUnhandledExceptionsWithRequestContextAndRethrows()
         Assert.Equal("exception-user", batchItem.GetProperty("distinct_id").GetString());
         var properties = batchItem.GetProperty("properties");
         Assert.Equal("exception-session", properties.GetProperty("$session_id").GetString());
-        Assert.Equal("https://example.com/api/test", properties.GetProperty("$current_url").GetString());
+        Assert.Equal("https://example.com/api/test?filter=1", properties.GetProperty("$current_url").GetString());
         Assert.Equal("ExceptionAgent/1.0", properties.GetProperty("$user_agent").GetString());
         Assert.Equal("10.0.0.2", properties.GetProperty("$ip").GetString());
         Assert.Equal(StatusCodes.Status503ServiceUnavailable, properties.GetProperty("$response_status_code").GetInt32());

tests/UnitTests/PostHogContextTests.cs

@@ -100,26 +100,21 @@ public async Task ExplicitCaptureValuesOverrideContext()
         Assert.Equal("context-only-value", properties.GetProperty("context-only").GetString());
     }
 
-    [Fact]
-    public void MissingDistinctIdCreatesPersonlessContext()
+    [Theory]
+    [InlineData(null, false)]
+    [InlineData(true, true)]
+    public void PersonlessContextSetsProcessPersonProfile(bool? explicitOverride, bool expectedValue)
     {
-        var context = PostHogContextHelper.ResolveCaptureContext(distinctId: null, properties: null);
+        var properties = explicitOverride.HasValue
+            ? new Dictionary<string, object> { ["$process_person_profile"] = explicitOverride.Value }
+            : null;
+
+        var context = PostHogContextHelper.ResolveCaptureContext(distinctId: null, properties: properties);
 
         Assert.True(Guid.TryParse(context.DistinctId, out _));
         Assert.True(context.IsPersonless);
         Assert.NotNull(context.Properties);
-        Assert.False((bool)context.Properties["$process_person_profile"]);
-    }
-
-    [Fact]
-    public void ExplicitProcessPersonProfileOverridesPersonlessDefault()
-    {
-        var context = PostHogContextHelper.ResolveCaptureContext(
-            distinctId: null,
-            properties: new Dictionary<string, object> { ["$process_person_profile"] = true });
-
-        Assert.NotNull(context.Properties);
-        Assert.True((bool)context.Properties["$process_person_profile"]);
+        Assert.Equal(expectedValue, (bool)context.Properties["$process_person_profile"]);
     }
 
     [Fact]