Fix for GetDefaultSortOrder not firing

src/JsonApiDotNetCore/Models/ResourceDefinition.cs

@@ -13,7 +13,7 @@ public interface IResourceDefinition
         List<AttrAttribute> GetAllowedAttributes();
         List<RelationshipAttribute> GetAllowedRelationships();
         object GetCustomQueryFilter(string key);
-        List<(AttrAttribute, SortDirection)> DefaultSort();
+        List<(AttrAttribute Attribute, SortDirection SortDirection)> DefaultSort();
     }
 
     /// <summary>
@@ -146,14 +146,16 @@ public sealed class QueryFilters : Dictionary<string, Func<IQueryable<TResource>
         /// </example>
         public virtual PropertySortOrder GetDefaultSortOrder() => null;
 
-        public List<(AttrAttribute, SortDirection)> DefaultSort()
+        public List<(AttrAttribute Attribute, SortDirection SortDirection)> DefaultSort()
         {
             var defaultSortOrder = GetDefaultSortOrder();
             if (defaultSortOrder != null && defaultSortOrder.Count > 0)
             {
-                var order = new List<(AttrAttribute, SortDirection)>();
+                var order = new List<(AttrAttribute Attribute, SortDirection SortDirection)>();
                 foreach (var sortProp in defaultSortOrder)
-                    order.Add((_resourceGraph.GetAttributes(sortProp.Item1).Single(), sortProp.Item2));
+                {
+                    order.Add((_resourceGraph.GetAttributes(sortProp.Attribute).Single(), sortProp.SortDirection));
+                }
 
                 return order;
             }
@@ -166,6 +168,6 @@ public sealed class QueryFilters : Dictionary<string, Func<IQueryable<TResource>
         /// method signature.
         /// See <see cref="GetQueryFilters" /> for usage details.
         /// </summary>
-        public sealed class PropertySortOrder : List<(Expression<Func<TResource, dynamic>>, SortDirection)> { }
+        public sealed class PropertySortOrder : List<(Expression<Func<TResource, dynamic>> Attribute, SortDirection SortDirection)> { }
     }
 }

src/JsonApiDotNetCore/QueryParameterServices/SortService.cs

@@ -29,11 +29,11 @@ public SortService(IResourceDefinitionProvider resourceDefinitionProvider,
         /// <inheritdoc/>
         public List<SortQueryContext> Get()
         {
-            if (_queries == null)
+            if (!_queries.Any())
             {
                 var requestResourceDefinition = _resourceDefinitionProvider.Get(_requestResource.ResourceType);
                 if (requestResourceDefinition != null)
-                    return requestResourceDefinition.DefaultSort()?.Select(d => BuildQueryContext(new SortQuery(d.Item1.PublicAttributeName, d.Item2))).ToList();
+                    return requestResourceDefinition.DefaultSort()?.Select(d => BuildQueryContext(new SortQuery(d.Attribute.PublicAttributeName, d.SortDirection))).ToList();
             }
             return _queries.ToList();
         }

test/UnitTests/Models/ResourceDefinitionTests.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using JsonApiDotNetCore.Builders;
 using JsonApiDotNetCore.Internal.Query;
 using JsonApiDotNetCore.Models;
@@ -10,6 +11,25 @@ namespace UnitTests.Models
 {
     public sealed class ResourceDefinition_Scenario_Tests
     {
+        [Fact]
+        public void Property_Sort_Order_Uses_NewExpression()
+        {
+            // Arrange
+            var resource = new RequestFilteredResource(isAdmin: false);
+
+            // Act
+            var sorts = resource.DefaultSort();
+
+            // Assert
+            Assert.Equal(2, sorts.Count);
+
+            Assert.Equal(nameof(Model.Prop), sorts[0].Attribute.PropertyInfo.Name);
+            Assert.Equal(SortDirection.Ascending, sorts[0].SortDirection);
+
+            Assert.Equal(nameof(Model.Password), sorts[1].Attribute.PropertyInfo.Name);
+            Assert.Equal(SortDirection.Descending, sorts[1].SortDirection);
+        }
+
         [Fact]
         public void Request_Filter_Uses_Member_Expression()
         {
@@ -63,7 +83,8 @@ public override QueryFilters GetQueryFilters()
             };
         public override PropertySortOrder GetDefaultSortOrder()
             => new PropertySortOrder {
-                (t => t.Prop, SortDirection.Ascending)
+                (t => t.Prop, SortDirection.Ascending),
+                (t => t.Password, SortDirection.Descending)
             };
     }
 }