fix issue with empty EntityFilter

Author: pwelter34

src/MediatR.CommandQuery/Queries/EntityFilter.cs

@@ -22,6 +22,7 @@ public class EntityFilter
     [JsonPropertyName("filters")]
     public IList<EntityFilter>? Filters { get; set; }
 
+    public bool IsValid() => (Filters?.Any(f => f.IsValid()) == true) || (Name is not null);
 
     public override int GetHashCode()
     {

src/MediatR.CommandQuery/Queries/LinqExpressionBuilder.cs

@@ -26,7 +26,7 @@ public class LinqExpressionBuilder
     };
 
     private readonly StringBuilder _expression = new();
-    private readonly List<object?> _values = new();
+    private readonly List<object?> _values = [];
 
     /// <summary>
     /// Gets the expression parameters.
@@ -68,6 +68,7 @@ private void Visit(EntityFilter entityFilter)
         WriteExpression(entityFilter);
     }
 
+    [System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "MA0051:Method is too long", Justification = "Expression Logic")]
     private void WriteExpression(EntityFilter entityFilter)
     {
         // name require for expression
@@ -137,10 +138,8 @@ private void WriteExpression(EntityFilter entityFilter)
     private bool WriteGroup(EntityFilter entityFilter)
     {
         // check for group start
-        var filters = entityFilter.Filters;
-
-        var hasGroup = filters?.Count > 0;
-        if (!hasGroup)
+        var filters = entityFilter.Filters?.Where(f => f.IsValid());
+        if (filters?.Any() != true)
             return false;
 
         var logic = string.IsNullOrWhiteSpace(entityFilter.Logic)
@@ -149,9 +148,6 @@ private bool WriteGroup(EntityFilter entityFilter)
 
         var wroteFirst = false;
 
-        if (filters == null)
-            return false;
-
         _expression.Append('(');
         foreach (var filter in filters)
         {

test/MediatR.CommandQuery.Tests/Queries/LinqExpressionBuilderTest.cs

@@ -25,11 +25,11 @@ public void FilterLogicalOr()
         var entityFilter = new EntityFilter
         {
             Logic = "or",
-            Filters = new List<EntityFilter>
-            {
+            Filters =
+            [
                 new EntityFilter{ Name = "Rank", Value = 7 },
                 new EntityFilter{ Name = "Name", Value = "Apple" }
-            }
+            ]
         };
 
         var builder = new LinqExpressionBuilder();
@@ -48,11 +48,11 @@ public void FilterLogicalAnd()
     {
         var entityFilter = new EntityFilter
         {
-            Filters = new List<EntityFilter>
-            {
+            Filters =
+            [
                 new EntityFilter{ Name = "Rank", Value = 7 },
                 new EntityFilter{ Name = "Name", Value = "Blueberry" }
-            }
+            ]
 
         };
 
@@ -67,24 +67,47 @@ public void FilterLogicalAnd()
         builder.Parameters[1].Should().Be("Blueberry");
     }
 
+    [Fact]
+    public void FilterLogicalAndEmpty()
+    {
+        var entityFilter = new EntityFilter
+        {
+            Filters =
+            [
+                new EntityFilter(),
+                new EntityFilter{ Name = "Name", Value = "Blueberry" }
+            ]
+
+        };
+
+        var builder = new LinqExpressionBuilder();
+        builder.Build(entityFilter);
+
+        builder.Expression.Should().NotBeEmpty();
+        builder.Expression.Should().Be("(Name == @0)");
+
+        builder.Parameters.Count.Should().Be(1);
+        builder.Parameters[0].Should().Be("Blueberry");
+    }
+
     [Fact]
     public void FilterComplex()
     {
         var entityFilter = new EntityFilter
         {
-            Filters = new List<EntityFilter>
-            {
+            Filters =
+            [
                 new EntityFilter{ Name = "Rank", Operator = ">", Value = 5 },
                 new EntityFilter
                 {
                     Logic = "or",
-                    Filters = new List<EntityFilter>
-                    {
+                    Filters =
+                    [
                         new EntityFilter{ Name = "Name", Value = "Strawberry" },
                         new EntityFilter{ Name = "Name", Value = "Blueberry" }
-                    }
+                    ]
                 }
-            }
+            ]
         };
 
         var builder = new LinqExpressionBuilder();
@@ -99,6 +122,36 @@ public void FilterComplex()
         builder.Parameters[2].Should().Be("Blueberry");
     }
 
+    [Fact]
+    public void FilterComplexEmpty()
+    {
+        var entityFilter = new EntityFilter
+        {
+            Filters =
+            [
+                new EntityFilter{ Name = "Rank", Operator = ">", Value = 5 },
+                new EntityFilter
+                {
+                    Logic = "or",
+                    Filters =
+                    [
+                        new EntityFilter(),
+                        new EntityFilter()
+                    ]
+                }
+            ]
+        };
+
+        var builder = new LinqExpressionBuilder();
+        builder.Build(entityFilter);
+
+        builder.Expression.Should().NotBeEmpty();
+        builder.Expression.Should().Be("(Rank > @0)");
+
+        builder.Parameters.Count.Should().Be(1);
+        builder.Parameters[0].Should().Be(5);
+    }
+
     [Fact]
     public void FilterContains()
     {