[Instrumentation.AspNetCore] Fix http.route for HTTP server spans

src/OpenTelemetry.Instrumentation.AspNetCore/Implementation/HttpInListener.cs

@@ -244,12 +244,12 @@ public void OnStopActivity(Activity activity, object? payload)
             var response = context.Response;
 
 #if !NETSTANDARD
-            var routePattern = (context.Features.Get<IExceptionHandlerPathFeature>()?.Endpoint as RouteEndpoint ??
-                    context.GetEndpoint() as RouteEndpoint)?.RoutePattern.RawText;
-            if (!string.IsNullOrEmpty(routePattern))
+            var endpoint = context.Features.Get<IExceptionHandlerPathFeature>()?.Endpoint as RouteEndpoint
+                ?? context.GetEndpoint() as RouteEndpoint;
+
+            if (endpoint != null)
             {
-                TelemetryHelper.RequestDataHelper.SetActivityDisplayName(activity, context.Request.Method, routePattern);
-                activity.SetTag(SemanticConventions.AttributeHttpRoute, routePattern);
+                activity.SetRouteAttributeTag(endpoint, context.Request);
             }
 #endif
 

src/OpenTelemetry.Instrumentation.AspNetCore/Implementation/HttpInMetricsListener.cs

@@ -94,11 +94,12 @@ public static void OnStopEventWritten(string name, object? payload)
 
 #if NET
         // Check the exception handler feature first in case the endpoint was overwritten
-        var route = (context.Features.Get<IExceptionHandlerPathFeature>()?.Endpoint as RouteEndpoint ??
-                     context.GetEndpoint() as RouteEndpoint)?.RoutePattern.RawText;
-        if (!string.IsNullOrEmpty(route))
+        var endpoint = context.Features.Get<IExceptionHandlerPathFeature>()?.Endpoint as RouteEndpoint
+            ?? context.GetEndpoint() as RouteEndpoint;
+
+        if (endpoint != null)
         {
-            tags.Add(new KeyValuePair<string, object?>(SemanticConventions.AttributeHttpRoute, route));
+            tags.AddRouteAttribute(endpoint, context.Request);
         }
 #endif
         if (context.Items.TryGetValue(ErrorTypeHttpContextItemsKey, out var errorType))

src/OpenTelemetry.Instrumentation.AspNetCore/Implementation/RouteAttributeHelper.cs

@@ -0,0 +1,100 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#if !NETSTANDARD
+
+using System.Diagnostics;
+using System.Text;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.AspNetCore.Routing.Patterns;
+using OpenTelemetry.Trace;
+
+namespace OpenTelemetry.Instrumentation.AspNetCore.Implementation;
+
+internal static class RouteAttributeHelper
+{
+    public static void AddRouteAttribute(this TagList tags, RouteEndpoint endpoint, HttpRequest request)
+    {
+        var routePattern = GetRoutePattern(endpoint.RoutePattern, request.RouteValues);
+
+        if (!string.IsNullOrEmpty(routePattern))
+        {
+            tags.Add(new KeyValuePair<string, object?>(SemanticConventions.AttributeHttpRoute, routePattern));
+        }
+    }
+
+    public static void SetRouteAttributeTag(this Activity activity, RouteEndpoint endpoint, HttpRequest request)
+    {
+        var routePattern = GetRoutePattern(endpoint.RoutePattern, request.RouteValues);
+
+        if (!string.IsNullOrEmpty(routePattern))
+        {
+            TelemetryHelper.RequestDataHelper.SetActivityDisplayName(activity, request.Method, routePattern);
+            activity.SetTag(SemanticConventions.AttributeHttpRoute, routePattern);
+        }
+    }
+
+    private static string GetRoutePattern(RoutePattern routePattern, RouteValueDictionary routeValues)
+    {
+        if (routePattern.PathSegments.Count == 0)
+        {
+            // RazorPage default route
+            if (routePattern.Defaults.TryGetValue("page", out var pageValue))
+            {
+                return pageValue?.ToString()?.Trim('/')
+                    ?? string.Empty;
+            }
+
+            return string.Empty;
+        }
+
+        var sb = new StringBuilder();
+
+        foreach (var segment in routePattern.PathSegments)
+        {
+            foreach (var part in segment.Parts)
+            {
+                if (part is RoutePatternLiteralPart literalPart)
+                {
+                    sb.Append(literalPart.Content);
+                    sb.Append('/');
+                }
+                else if (part is RoutePatternParameterPart parameterPart)
+                {
+                    switch (parameterPart.Name)
+                    {
+                        case "area":
+                        case "controller":
+                        case "action":
+                            routePattern.RequiredValues.TryGetValue(parameterPart.Name, out var parameterValue);
+                            if (parameterValue != null)
+                            {
+                                sb.Append(parameterValue);
+                                sb.Append('/');
+                                break;
+                            }
+
+                            goto default;
+                        default:
+                            if (!parameterPart.IsOptional ||
+                                (parameterPart.IsOptional && routeValues.ContainsKey(parameterPart.Name)))
+                            {
+                                sb.Append('{');
+                                sb.Append(parameterPart.Name);
+                                sb.Append('}');
+                                sb.Append('/');
+                            }
+
+                            break;
+                    }
+                }
+            }
+        }
+
+        // Remove the trailing '/'
+        return sb.ToString(0, sb.Length - 1);
+    }
+}
+
+#endif