stop excluding null values when filtering using notEqual (#114)

* stop excluding null values when filtering using notEqual
* add IgnoreNullsOnNotEqual config field, to enable/disable the new feature

Co-authored-by: AnasZakarneh <a.zakarneh@foothillsolutions.com>

README.md

@@ -127,7 +127,8 @@ Then you can add the configuration:
         "CaseSensitive": "boolean: should property names be case-sensitive? Defaults to false",
         "DefaultPageSize": "int number: optional number to fallback to when no page argument is given. Set <=0 to disable paging if no pageSize is specified (default).",
         "MaxPageSize": "int number: maximum allowed page size. Set <=0 to make infinite (default)",
-        "ThrowExceptions": "boolean: should Sieve throw exceptions instead of silently failing? Defaults to false"
+        "ThrowExceptions": "boolean: should Sieve throw exceptions instead of silently failing? Defaults to false",
+        "IgnoreNullsOnNotEqual": "boolean: ignore null values when filtering using is not equal operator? Default to true"
     }
 }
 ```

Sieve.Sample/appsettings.json

@@ -4,7 +4,8 @@
   },
   "Sieve": {
     "CaseSensitive": false,
-    "DefaultPageSize": 10
+    "DefaultPageSize": 10,
+    "IgnoreNullsOnNotEqual": true
   },
   "Logging": {
     "Debug": {

Sieve/Models/SieveOptions.cs

@@ -9,5 +9,7 @@
         public int MaxPageSize { get; set; } = 0;
 
         public bool ThrowExceptions { get; set; } = false;
+
+        public bool IgnoreNullsOnNotEqual { get; set; } = true;
     }
 }

Sieve/Services/SieveProcessor.cs

@@ -217,11 +217,14 @@ namespace Sieve.Services
                                 expression = Expression.Not(expression);
                             }
 
+                            if (expression.NodeType != ExpressionType.NotEqual || Options.Value.IgnoreNullsOnNotEqual)
+                            {
                                 var filterValueNullCheck = GetFilterValueNullCheck(parameter, fullPropertyName, isFilterTermValueNull);
                                 if (filterValueNullCheck != null)
                                 {
                                     expression = Expression.AndAlso(filterValueNullCheck, expression);
                                 }
+                            }
 
                             innerExpression = innerExpression == null
                                 ? expression
@@ -254,8 +257,7 @@ namespace Sieve.Services
                 : result.Where(Expression.Lambda<Func<TEntity, bool>>(outerExpression, parameter));
         }
 
-        private static Expression GetFilterValueNullCheck(Expression parameter, string fullPropertyName,
+        private static Expression GetFilterValueNullCheck(Expression parameter, string fullPropertyName, bool isFilterTermValueNull)
-            bool isFilterTermValueNull)
         {
             var (propertyValue, nullCheck) = GetPropertyValueAndNullCheckExpression(parameter, fullPropertyName);
 

SieveUnitTests/General.cs

@@ -15,16 +15,24 @@ namespace SieveUnitTests
     {
         private readonly ITestOutputHelper _testOutputHelper;
         private readonly SieveProcessor _processor;
+        private readonly SieveProcessor _nullableProcessor;
         private readonly IQueryable<Post> _posts;
         private readonly IQueryable<Comment> _comments;
 
         public General(ITestOutputHelper testOutputHelper)
         {
+            var nullableAccessor = new SieveOptionsAccessor();
+            nullableAccessor.Value.IgnoreNullsOnNotEqual = false;
+
             _testOutputHelper = testOutputHelper;
             _processor = new ApplicationSieveProcessor(new SieveOptionsAccessor(),
                 new SieveCustomSortMethods(),
                 new SieveCustomFilterMethods());
 
+            _nullableProcessor = new ApplicationSieveProcessor(nullableAccessor,
+                new SieveCustomSortMethods(),
+                new SieveCustomFilterMethods());
+
             _posts = new List<Post>
             {
                 new Post
@@ -180,8 +188,25 @@ namespace SieveUnitTests
             };
 
             var result = _processor.Apply(model, _posts);
+            var nullableResult = _nullableProcessor.Apply(model, _posts);
 
             Assert.True(result.Count() == 2);
+            Assert.True(nullableResult.Count() == 2);
+        }
+
+        [Fact]
+        public void CanFilterNullableIntsWithNotEqual()
+        {
+            var model = new SieveModel()
+            {
+                Filters = "CategoryId!=1"
+            };
+
+            var result = _processor.Apply(model, _posts);
+            var nullableResult = _nullableProcessor.Apply(model, _posts);
+
+            Assert.True(result.Count() == 1);
+            Assert.True(nullableResult.Count() == 2);
         }
 
         [Theory]

SieveUnitTests/GeneralWithInterfaces.cs

@@ -16,16 +16,24 @@ namespace SieveUnitTests
     {
         private readonly ITestOutputHelper _testOutputHelper;
         private readonly SieveProcessor _processor;
+        private readonly SieveProcessor _nullableProcessor;
         private readonly IQueryable<IPost> _posts;
         private readonly IQueryable<Comment> _comments;
 
         public GeneralWithInterfaces(ITestOutputHelper testOutputHelper)
         {
+            var nullableAccessor = new SieveOptionsAccessor();
+            nullableAccessor.Value.IgnoreNullsOnNotEqual = false;
+
             _testOutputHelper = testOutputHelper;
             _processor = new ApplicationSieveProcessor(new SieveOptionsAccessor(),
                 new SieveCustomSortMethods(),
                 new SieveCustomFilterMethods());
 
+            _nullableProcessor = new ApplicationSieveProcessor(nullableAccessor,
+                new SieveCustomSortMethods(),
+                new SieveCustomFilterMethods());
+
             _posts = new List<IPost>
             {
                 new Post
@@ -181,8 +189,25 @@ namespace SieveUnitTests
             };
 
             var result = _processor.Apply(model, _posts);
+            var nullableResult = _nullableProcessor.Apply(model, _posts);
 
             Assert.True(result.Count() == 2);
+            Assert.True(nullableResult.Count() == 2);
+        }
+
+        [Fact]
+        public void CanFilterNullableIntsWithNotEqual()
+        {
+            var model = new SieveModel()
+            {
+                Filters = "CategoryId!=1"
+            };
+
+            var result = _processor.Apply(model, _posts);
+            var nullableResult = _nullableProcessor.Apply(model, _posts);
+
+            Assert.True(result.Count() == 1);
+            Assert.True(nullableResult.Count() == 2);
         }
 
         [Fact]