Actually use attribute-based suppression

Author: captainsafia

src/Http/Routing/src/ValidationEndpointFilterFactory.cs

@@ -2,14 +2,17 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.ComponentModel.DataAnnotations;
-using System.Linq;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 
 namespace Microsoft.AspNetCore.Http.Validation;
 
 internal static class ValidationEndpointFilterFactory
 {
+    private const string ValidationContextJustification = "The DisplayName property is always statically initialized in the ValidationContext through this codepath.";
+
+    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = ValidationContextJustification)]
     public static EndpointFilterDelegate Create(EndpointFilterFactoryContext context, EndpointFilterDelegate next)
     {
         var parameters = context.MethodInfo.GetParameters();
@@ -18,33 +21,44 @@ public static EndpointFilterDelegate Create(EndpointFilterFactoryContext context
         {
             return next;
         }
-        var validatableParameters = parameters
-            .Select(p => options.TryGetValidatableParameterInfo(p, out var validatableParameter) ? validatableParameter : null);
-        if (validatableParameters.All(p => p is null))
+
+        var parameterCount = parameters.Length;
+        var validatableParameters = new ValidatableParameterInfo[parameterCount];
+        var hasValidatableParameters = false;
+
+        for (var i = 0; i < parameterCount; i++)
+        {
+            if (options.TryGetValidatableParameterInfo(parameters[i], out var validatableParameter))
+            {
+                validatableParameters[i] = validatableParameter;
+                hasValidatableParameters = true;
+            }
+        }
+
+        if (!hasValidatableParameters)
         {
             return next;
         }
+
         var validatableContext = new ValidatableContext { ValidationOptions = options };
         return async (context) =>
         {
             validatableContext.ValidationErrors?.Clear();
 
             for (var i = 0; i < context.Arguments.Count; i++)
             {
-                var validatableParameter = validatableParameters.ElementAt(i);
+                var validatableParameter = validatableParameters[i];
 
                 var argument = context.Arguments[i];
                 if (argument is null || validatableParameter is null)
                 {
                     continue;
                 }
-#pragma warning disable IL2026 // Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code
                 // ValidationContext is not trim-friendly in codepaths that don't
                 // initialize an explicit DisplayName. We can suppress the warning here.
                 // Eventually, this can be removed when the code is updated to
                 // use https://github.com/dotnet/runtime/issues/113134.
                 var validationContext = new ValidationContext(argument, context.HttpContext.RequestServices, items: null) { DisplayName = validatableParameter.DisplayName };
-#pragma warning restore IL2026 // Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code
                 validatableContext.ValidationContext = validationContext;
                 await validatableParameter.Validate(argument, validatableContext);
             }