Handling local constant expression. (#181)

Author: BlaiseD

src/AutoMapper.Extensions.ExpressionMapping/XpressionMapperVisitor.cs

@@ -538,6 +538,9 @@ protected override Expression VisitConstant(ConstantExpression node)
                     return base.VisitConstant(Expression.Constant(Mapper.MapObject(node.Value, node.Type, newType), newType));
                 //Issue 3455 (Non-Generic Mapper.Map failing for structs in v10)
                 //return base.VisitConstant(Expression.Constant(Mapper.Map(node.Value, node.Type, newType), newType));
+
+                if (typeof(Expression).IsAssignableFrom(node.Type))
+                    return Expression.Constant(this.Visit((Expression)node.Value), newType);
             }
             return base.VisitConstant(node);
         }

tests/AutoMapper.Extensions.ExpressionMapping.UnitTests/CanMapExpressionWithLocalExpressionConstant.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using Xunit;
+
+namespace AutoMapper.Extensions.ExpressionMapping.UnitTests
+{
+    public class CanMapExpressionWithLocalExpressionConstant
+    {
+        [Fact]
+        public void Map_expression_wchich_includes_local_constant()
+        {
+            //Arrange
+            var config = new MapperConfiguration
+            (
+                cfg =>
+                {
+                    cfg.CreateMap<EntityModel, Entity>();
+                    cfg.CreateMap<Entity, EntityModel>();
+                }
+            );
+            config.AssertConfigurationIsValid();
+            var mapper = config.CreateMapper();
+            List<Entity> source = [
+                new Entity { Id = 1 },
+                new Entity { Id = 3 }
+            ];
+
+            //act
+            Expression<Func<EntityModel, bool>> filter = f => f.Id > 2;
+            Expression<Func<IQueryable<EntityModel>, IQueryable<EntityModel>>> queryableExpression = q => q.Where(filter);
+            Expression<Func<IQueryable<Entity>, IQueryable<Entity>>> queryableExpressionMapped = mapper.MapExpression<Expression<Func<IQueryable<Entity>, IQueryable<Entity>>>>(queryableExpression);
+
+            //assert
+            Assert.Equal(1, queryableExpressionMapped.Compile()(source.AsQueryable()).Count());
+        }
+
+        public record Entity
+        {
+            public int Id { get; init; }
+        }
+
+        public record EntityModel
+        {
+            public int Id { get; init; }
+        }
+    }
+}