Set default type earlier

Author: captainsafia

src/OpenApi/src/Services/OpenApiDocumentService.cs

@@ -409,6 +409,10 @@ private async Task<OpenApiResponse> GetResponseAsync(
             var targetType = parameter.Type == typeof(string) && parameter.ModelMetadata.ModelType != parameter.Type
                 ? parameter.ModelMetadata.ModelType
                 : parameter.Type;
+            // If the type is null, then we're dealing with an inert
+            // route parameter that does not define a specific parameter type in the
+            // route handler or in the response. In this case, we default to a string schema.
+            targetType ??= typeof(string);
             var openApiParameter = new OpenApiParameter
             {
                 Name = parameter.Name,

src/OpenApi/src/Services/Schemas/OpenApiSchemaService.cs

@@ -126,15 +126,8 @@ internal sealed class OpenApiSchemaService(
         }
     };
 
-    internal async Task<OpenApiSchema> GetOrCreateSchemaAsync(Type? type, IServiceProvider scopedServiceProvider, IOpenApiSchemaTransformer[] schemaTransformers, ApiParameterDescription? parameterDescription = null, bool captureSchemaByRef = false, CancellationToken cancellationToken = default)
+    internal async Task<OpenApiSchema> GetOrCreateSchemaAsync(Type type, IServiceProvider scopedServiceProvider, IOpenApiSchemaTransformer[] schemaTransformers, ApiParameterDescription? parameterDescription = null, bool captureSchemaByRef = false, CancellationToken cancellationToken = default)
     {
-        // If the type is null, then we're dealing with an ambient
-        // route parameter that does not define a specific parameter type in the
-        // route handler or in the response. In this case, we default to a string schema.
-        if (type is null)
-        {
-            return new OpenApiSchema { Type = "string" };
-        }
         var key = parameterDescription?.ParameterDescriptor is IParameterInfoParameterDescriptor parameterInfoDescription
             && parameterDescription.ModelMetadata.PropertyName is null
             ? new OpenApiSchemaKey(type, parameterInfoDescription.ParameterInfo) : new OpenApiSchemaKey(type, null);