Use the new .NET api to check for nullable reference types

src/HotChocolate/Core/src/Execution/Projections/SelectionExpressionBuilder.cs

@@ -11,6 +11,8 @@ namespace HotChocolate.Execution.Projections;
 
 internal sealed class SelectionExpressionBuilder
 {
+    private static readonly NullabilityInfoContext _nullabilityInfoContext = new();
+
     public Expression<Func<TRoot, TRoot>> BuildExpression<TRoot>(ISelection selection)
     {
         var rootType = typeof(TRoot);
@@ -291,14 +293,9 @@ private static bool IsNullableType(PropertyInfo propertyInfo)
             return Nullable.GetUnderlyingType(propertyInfo.PropertyType) != null;
         }
 
-        var nullableAttribute = propertyInfo.GetCustomAttribute<NullableAttribute>();
-
-        if (nullableAttribute != null)
-        {
-            return nullableAttribute.NullableFlags[0] == 2;
-        }
+        var nullabilityInfo = _nullabilityInfoContext.Create(propertyInfo);
 
-        return false;
+        return nullabilityInfo.WriteState == NullabilityState.Nullable;
     }
 
     private readonly record struct Context(

src/HotChocolate/Core/test/Execution.Tests/Projections/ProjectableDataLoaderTests.cs

@@ -759,6 +759,39 @@ public async Task Project_Key_To_Collection_Expression_Integration()
             .MatchMarkdownSnapshot();
     }
 
+    [Fact]
+    public async Task Product_With_Nullable_Reference_Property_Set_To_Null()
+    {
+        // Arrange
+        var queries = new List<string>();
+        var connectionString = CreateConnectionString();
+        await CatalogContext.SeedAsync(connectionString);
+
+        // Act
+        var result = await new ServiceCollection()
+            .AddScoped(_ => queries)
+            .AddTransient(_ => new CatalogContext(connectionString))
+            .AddGraphQLServer()
+            .AddQueryType<ProductsWithNullPropertyQuery>()
+            .ExecuteRequestAsync(
+                """
+                {
+                    productById(id: 1) {
+                        name
+                        type {
+                            name
+                        }
+                    }
+                }
+                """);
+
+        // Assert
+        Snapshot.Create()
+            .AddSql(queries)
+            .Add(result, "Result")
+            .MatchMarkdownSnapshot();
+    }
+
     public class Query
     {
         public async Task<Brand?> GetBrandByIdAsync(
@@ -836,6 +869,39 @@ public async Task<IEnumerable<Brand>> GetBrandByIdAsync(
                 .ToListAsync(cancellationToken);
     }
 
+    public class ProductsWithNullPropertyQuery
+    {
+        public async Task<ProductProjection?> GetProductByIdAsync(
+            int id,
+            List<string> queries,
+            ISelection selection,
+            CatalogContext context,
+            CancellationToken cancellationToken)
+        {
+            var query = context.Products
+                .Where(p => p.Id == id)
+                .Select(p => new ProductProjection // Cast to an object with nullable Type property
+                {
+                    Name = p.Name,
+                })
+                .Select(selection.AsSelector<ProductProjection>());
+
+            lock (queries)
+            {
+                queries.Add(query.ToQueryString());
+            }
+
+            return await query.SingleOrDefaultAsync(cancellationToken);
+        }
+
+        public class ProductProjection
+        {
+            public string Name { get; set; } = default!;
+
+            public ProductType? Type { get; set; }
+        }
+    }
+
     [ExtendObjectType<Brand>]
     public class BrandExtensions
     {

src/HotChocolate/Core/test/Execution.Tests/Projections/__snapshots__/ProjectableDataLoaderTests.Branches_Are_Merged.md

@@ -4,7 +4,7 @@
 
 ```text
 -- @__keys_0={ '1', '2' } (DbType = Object)
-SELECT p."Name", b."Name", p."Id"
+SELECT p."Name", FALSE, b."Name", p."Id"
 FROM "Products" AS p
 INNER JOIN "Brands" AS b ON p."BrandId" = b."Id"
 WHERE p."Id" = ANY (@__keys_0)

src/HotChocolate/Core/test/Execution.Tests/Projections/__snapshots__/ProjectableDataLoaderTests.Force_A_Branch.md

@@ -4,12 +4,12 @@
 
 ```text
 -- @__keys_0={ '1' } (DbType = Object)
-SELECT p."Name", b."Name", p."Id"
+SELECT p."Name", FALSE, b."Name", p."Id"
 FROM "Products" AS p
 INNER JOIN "Brands" AS b ON p."BrandId" = b."Id"
 WHERE p."Id" = ANY (@__keys_0)
 -- @__keys_0={ '1' } (DbType = Object)
-SELECT p."Id", b."Id"
+SELECT p."Id", FALSE, b."Id"
 FROM "Products" AS p
 INNER JOIN "Brands" AS b ON p."BrandId" = b."Id"
 WHERE p."Id" = ANY (@__keys_0)

src/HotChocolate/Core/test/Execution.Tests/Projections/__snapshots__/ProjectableDataLoaderTests.Product_With_Name_And_Brand_With_Name.md

@@ -4,7 +4,7 @@
 
 ```text
 -- @__keys_0={ '1' } (DbType = Object)
-SELECT p."Name", b."Name", p."Id"
+SELECT p."Name", FALSE, b."Name", p."Id"
 FROM "Products" AS p
 INNER JOIN "Brands" AS b ON p."BrandId" = b."Id"
 WHERE p."Id" = ANY (@__keys_0)

src/HotChocolate/Core/test/Execution.Tests/Projections/__snapshots__/ProjectableDataLoaderTests.Product_With_Nullable_Reference_Property_Set_To_Null.md

@@ -0,0 +1,24 @@
+# Product_With_Nullable_Reference_Property_Set_To_Null
+
+## SQL
+
+```text
+-- @__id_0='1'
+SELECT p."Name"
+FROM "Products" AS p
+WHERE p."Id" = @__id_0
+```
+
+## Result
+
+```json
+{
+  "data": {
+    "productById": {
+      "name": "Product 0-0",
+      "type": null
+    }
+  }
+}
+```
+

src/HotChocolate/Core/test/Execution.Tests/TestContext/Product.cs

@@ -34,10 +34,6 @@ public class Product
     // Maximum number of units that can be in-stock at any time (due to physicial/logistical constraints in warehouses)
     public int MaxStockThreshold { get; set; }
 
-    /// <summary>Optional embedding for the catalog item's description.</summary>
-    // [JsonIgnore]
-    // public Vector Embedding { get; set; }
-
     /// <summary>
     /// True if item is on reorder
     /// </summary>

src/HotChocolate/Pagination/test/Pagination.EntityFramework.Tests/__snapshots__/IntegrationPagingHelperTests.Ensure_Nullable_Connections_Dont_Throw.md

@@ -18,7 +18,7 @@ ORDER BY t."Name", t."Id"
 ## Expression 0
 
 ```text
-[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = root.Bar.Description})}).Take(11)
+[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = IIF((root.Bar.Description == null), null, root.Bar.Description)})}).Take(11)
 ```
 
 ## Result

src/HotChocolate/Pagination/test/Pagination.EntityFramework.Tests/__snapshots__/IntegrationPagingHelperTests.Ensure_Nullable_Connections_Dont_Throw_2.md

@@ -18,7 +18,7 @@ ORDER BY t."Name", t."Id"
 ## Expression 0
 
 ```text
-[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = root.Bar.Description, SomeField1 = root.Bar.SomeField1, SomeField2 = root.Bar.SomeField2})}).Take(11)
+[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = IIF((root.Bar.Description == null), null, root.Bar.Description), SomeField1 = root.Bar.SomeField1, SomeField2 = IIF((root.Bar.SomeField2 == null), null, root.Bar.SomeField2)})}).Take(11)
 ```
 
 ## Result

src/HotChocolate/Pagination/test/Pagination.EntityFramework.Tests/__snapshots__/IntegrationPagingHelperTests.Ensure_Nullable_Connections_Dont_Throw_2_NET9_0.md

@@ -18,7 +18,7 @@ ORDER BY f0."Name", f0."Id"
 ## Expression 0
 
 ```text
-[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = root.Bar.Description, SomeField1 = root.Bar.SomeField1, SomeField2 = root.Bar.SomeField2})}).Take(11)
+[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = IIF((root.Bar.Description == null), null, root.Bar.Description), SomeField1 = root.Bar.SomeField1, SomeField2 = IIF((root.Bar.SomeField2 == null), null, root.Bar.SomeField2)})}).Take(11)
 ```
 
 ## Result

src/HotChocolate/Pagination/test/Pagination.EntityFramework.Tests/__snapshots__/IntegrationPagingHelperTests.Ensure_Nullable_Connections_Dont_Throw_NET9_0.md

@@ -18,7 +18,7 @@ ORDER BY f0."Name", f0."Id"
 ## Expression 0
 
 ```text
-[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = root.Bar.Description})}).Take(11)
+[Microsoft.EntityFrameworkCore.Query.EntityQueryRootExpression].OrderBy(t => t.Name).ThenBy(t => t.Id).Select(root => new Foo() {Id = root.Id, Name = root.Name, Bar = IIF((root.Bar == null), null, new Bar() {Id = root.Bar.Id, Description = IIF((root.Bar.Description == null), null, root.Bar.Description)})}).Take(11)
 ```
 
 ## Result