Projection left joins now support nullable

src/HotChocolate/Data/src/Data/Projections/Expressions/Handlers/QueryableProjectionFieldHandler.cs

@@ -1,10 +1,12 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using System.Linq.Expressions;
 using System.Reflection;
 using HotChocolate.Execution.Processing;
 using HotChocolate.Types;
+using static HotChocolate.Data.Projections.Expressions.ProjectionExpressionBuilder;
 
 namespace HotChocolate.Data.Projections.Expressions.Handlers
 {
@@ -81,16 +83,30 @@ public class QueryableProjectionFieldHandler
 
             Queue<MemberAssignment> members = queryableScope.Level.Pop();
             MemberInitExpression memberInit =
-                ProjectionExpressionBuilder.CreateMemberInit(queryableScope.RuntimeType, members);
+                CreateMemberInit(queryableScope.RuntimeType, members);
 
             if (!context.TryGetQueryableScope(out QueryableProjectionScope? parentScope))
             {
                 throw new InvalidOperationException();
             }
 
+            Expression nestedProperty;
+            if (field.Member is PropertyInfo propertyInfo)
+            {
+                nestedProperty = Expression.Property(context.GetInstance(), propertyInfo);
+            }
+            else if (field.Member is MethodInfo methodInfo)
+            {
+                nestedProperty = Expression.Call(context.GetInstance(), methodInfo);
+            }
+            else
+            {
+                throw new InvalidOperationException();
+            }
+
             parentScope.Level.Peek()
                 .Enqueue(
-                    Expression.Bind(field.Member, memberInit));
+                    Expression.Bind(field.Member, NotNullAndAlso(nestedProperty, memberInit)));
 
             action = SelectionVisitor.Continue;
             return true;

src/HotChocolate/Data/src/Data/Projections/Expressions/ProjectionExpressionBuilder.cs

@@ -6,12 +6,28 @@ namespace HotChocolate.Data.Projections.Expressions
 {
     internal static class ProjectionExpressionBuilder
     {
+        private static readonly ConstantExpression _null =
+            Expression.Constant(null, typeof(object));
+
         public static MemberInitExpression CreateMemberInit(
             Type type,
             IEnumerable<MemberBinding> expressions)
         {
             NewExpression ctor = Expression.New(type);
             return Expression.MemberInit(ctor, expressions);
         }
+
+        public static Expression NotNull(Expression expression)
+        {
+            return Expression.NotEqual(expression, _null);
+        }
+
+        public static Expression NotNullAndAlso(Expression property, Expression condition)
+        {
+            return Expression.Condition(
+                NotNull(property),
+                condition,
+                Expression.Default(property.Type));
+        }
     }
 }