Replace static parameters in route pattern for telemetry

src/Http/Routing/src/Patterns/RoutePattern.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
-using System.Linq;
 using Microsoft.AspNetCore.Routing.Template;
 
 namespace Microsoft.AspNetCore.Routing.Patterns;
@@ -35,8 +34,6 @@ internal static bool IsRequiredValueAny(object? value)
         return object.ReferenceEquals(RequiredValueAny, value);
     }
 
-    private const string SeparatorString = "/";
-
     internal RoutePattern(
         string? rawText,
         IReadOnlyDictionary<string, object?> defaults,
@@ -158,10 +155,7 @@ internal RoutePattern(
     // 1. RoutePattern debug string.
     // 2. Default IRouteDiagnosticsMetadata value.
     // 3. RouteEndpoint display name.
-    internal string DebuggerToString()
-    {
-        return RawText ?? string.Join(SeparatorString, PathSegments.Select(s => s.DebuggerToString()));
-    }
+    internal string DebuggerToString() => RoutePatternDebugStringFormatter.Format(this);
 
     [DebuggerDisplay("{DebuggerToString(),nq}")]
     private sealed class RequiredValueAnySentinal

src/Http/Routing/src/Patterns/RoutePatternDebugStringFormatter.cs

@@ -0,0 +1,103 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.AspNetCore.Routing.Patterns;
+
+internal static class RoutePatternDebugStringFormatter
+{
+    private const char Separator = '/';
+    private const string SeparatorString = "/";
+
+    public static string Format(RoutePattern pattern)
+    {
+        // If there are no required values that match parameters, use the simple approach
+        if (pattern.RawText is { Length: > 0 } rawText && !HasMatchingRequiredValues(pattern))
+        {
+            return rawText;
+        }
+
+        // Build the string replacing parameters with their required values when available
+        var segments = new string[pattern.PathSegments.Count];
+        for (var i = 0; i < pattern.PathSegments.Count; i++)
+        {
+            var segment = pattern.PathSegments[i];
+            var segmentString = GetSegmentDebuggerToString(pattern, segment);
+            segments[i] = segmentString;
+        }
+
+        var result = string.Join(SeparatorString, segments);
+
+        // Preserve leading slash from raw text
+        if (pattern.RawText is { Length: > 0 } rt && rt[0] == Separator)
+        {
+            result = Separator + result;
+        }
+
+        // Return "/" for empty results
+        if (result.Length == 0)
+        {
+            return SeparatorString;
+        }
+
+        return result;
+    }
+
+    private static bool HasMatchingRequiredValues(RoutePattern pattern)
+    {
+        if (pattern.RequiredValues.Count == 0)
+        {
+            return false;
+        }
+
+        for (var i = 0; i < pattern.Parameters.Count; i++)
+        {
+            if (TryGetRequiredValue(pattern, pattern.Parameters[i].Name, out _))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private static string GetSegmentDebuggerToString(RoutePattern pattern, RoutePatternPathSegment segment)
+    {
+        // Simple segment with single parameter that has a required value - just return the required value
+        if (segment.IsSimple && segment.Parts[0] is RoutePatternParameterPart parameter)
+        {
+            if (TryGetRequiredValue(pattern, parameter.Name, out var requiredValue))
+            {
+                return requiredValue;
+            }
+            return parameter.DebuggerToString();
+        }
+
+        // For complex segments, build the string part by part
+        var parts = new string[segment.Parts.Count];
+        for (var i = 0; i < segment.Parts.Count; i++)
+        {
+            var part = segment.Parts[i];
+            parts[i] = part is RoutePatternParameterPart paramPart && TryGetRequiredValue(pattern, paramPart.Name, out var value)
+                ? value
+                : part.DebuggerToString();
+        }
+
+        return string.Join(string.Empty, parts);
+    }
+
+    private static bool TryGetRequiredValue(RoutePattern pattern, string parameterName, [NotNullWhen(true)] out string? value)
+    {
+        if (pattern.RequiredValues.TryGetValue(parameterName, out var requiredValue) &&
+            !RoutePattern.IsRequiredValueAny(requiredValue) &&
+            requiredValue?.ToString() is { Length: > 0 } v)
+        {
+            value = v;
+            return true;
+        }
+
+        value = null;
+        return false;
+    }
+}

src/Http/Routing/src/Patterns/RoutePatternParameterPart.cs

@@ -99,10 +99,23 @@ internal override string DebuggerToString()
         foreach (var constraint in ParameterPolicies)
         {
             builder.Append(':');
-            builder.Append(constraint.ParameterPolicy);
+            if (constraint.Content is not null)
+            {
+                builder.Append(constraint.Content);
+            }
+            else if (constraint.ParameterPolicy is Constraints.RegexRouteConstraint regexConstraint)
+            {
+                builder.Append("regex(");
+                builder.Append(regexConstraint.Constraint.ToString());
+                builder.Append(')');
+            }
+            else if (constraint.ParameterPolicy is not null)
+            {
+                builder.Append(constraint.ParameterPolicy);
+            }
         }
 
-        if (Default != null)
+        if (Default is not null)
         {
             builder.Append('=');
             builder.Append(Default);