Using GetValueOrDefault and skipping null check when mapping from nullable T to T

Author: SteveWilkes

AgileMapper.UnitTests/WhenViewingMappingPlans.cs

@@ -264,6 +264,7 @@ public void ShouldNotRangeCheckNullableToNonNullableValues()
             string plan = Mapper.GetPlanFor<PublicField<int?>>().ToANew<PublicField<int>>();
 
             plan.ShouldNotContain("int.MinValue");
+            plan.ShouldNotContain("Value.HasValue");
         }
 
         [Fact]

AgileMapper/Extensions/ExpressionExtensions.cs

@@ -156,7 +156,19 @@ public static Expression GetValueOrDefaultCall(this Expression nullableExpressio
 
         [DebuggerStepThrough]
         public static Expression GetConversionTo(this Expression expression, Type targetType)
-            => (expression.Type != targetType) ? Expression.Convert(expression, targetType) : expression;
+        {
+            if (expression.Type == targetType)
+            {
+                return expression;
+            }
+
+            if (expression.Type.GetNonNullableType() == targetType)
+            {
+                return expression.GetValueOrDefaultCall();
+            }
+
+            return Expression.Convert(expression, targetType);
+        }
 
         public static Expression WithToArrayCall(this Expression enumerable, Type elementType)
         {

AgileMapper/Members/ExpressionInfoFinder.cs

@@ -151,6 +151,11 @@ protected override Expression VisitMethodCall(MethodCallExpression methodCall)
                 if ((methodCall.Object != _mappingDataObject) &&
                     (methodCall.Method.DeclaringType != typeof(IMappingData)))
                 {
+                    if (IsNullableGetValueOrDefaultCall(methodCall))
+                    {
+                        AddExistingNullCheck(methodCall.Object);
+                    }
+
                     AddStringMemberAccessSubjectIfAppropriate(methodCall.Object);
                     AddInvocationIfNecessary(methodCall);
                     AddMemberAccessIfAppropriate(methodCall);
@@ -159,6 +164,13 @@ protected override Expression VisitMethodCall(MethodCallExpression methodCall)
                 return base.VisitMethodCall(methodCall);
             }
 
+            private static bool IsNullableGetValueOrDefaultCall(MethodCallExpression methodCall)
+            {
+                return (methodCall.Object != null) &&
+                       (methodCall.Method.Name == "GetValueOrDefault") &&
+                       (methodCall.Object.Type.IsNullableType());
+            }
+
             private void AddExistingNullCheck(Expression checkedAccess)
             {
                 _nullCheckSubjects.Add(checkedAccess.ToString());