Use TryConvertTypes also for strings (#938)

Author: StefH

src/System.Linq.Dynamic.Core/Parser/ExpressionHelper.cs

@@ -378,6 +378,26 @@ public Expression ConvertAnyArrayToObjectArray(Expression arrayExpression)
         );
     }
 
+    /// <inheritdoc/>
+    public bool TryConvertTypes(ref Expression left, ref Expression right)
+    {
+        if (!_parsingConfig.ConvertObjectToSupportComparison || left.Type == right.Type || Constants.IsNull(left) || Constants.IsNull(right))
+        {
+            return false;
+        }
+
+        if (left.Type == typeof(object))
+        {
+            left = Expression.Convert(left, right.Type);
+        }
+        else if (right.Type == typeof(object))
+        {
+            right = Expression.Convert(right, left.Type);
+        }
+
+        return true;
+    }
+
     private Expression? GetMemberExpression(Expression? expression)
     {
         if (ExpressionQualifiesForNullPropagation(expression))
@@ -455,26 +475,6 @@ private List<Expression> CollectExpressions(bool addSelf, Expression sourceExpre
         return list;
     }
 
-    /// <summary>
-    /// If the types are different (and not null), try to convert the object type to other type.
-    /// </summary>
-    private void TryConvertTypes(ref Expression left, ref Expression right)
-    {
-        if (!_parsingConfig.ConvertObjectToSupportComparison || left.Type == right.Type || Constants.IsNull(left) || Constants.IsNull(right))
-        {
-            return;
-        }
-
-        if (left.Type == typeof(object))
-        {
-            left = Expression.Convert(left, right.Type);
-        }
-        else if (right.Type == typeof(object))
-        {
-            right = Expression.Convert(right, left.Type);
-        }
-    }
-
     private static Expression GenerateStaticMethodCall(string methodName, Expression left, Expression right)
     {
         if (!TryGetStaticMethod(methodName, left, right, out var methodInfo))

src/System.Linq.Dynamic.Core/Parser/ExpressionParser.cs

@@ -527,7 +527,11 @@ private Expression ParseComparisonOperator()
                 // If left or right is NullLiteral, just continue. Else check if the types differ.
                 if (!(Constants.IsNull(left) || Constants.IsNull(right)) && left.Type != right.Type)
                 {
-                    if (left.Type.IsAssignableFrom(right.Type) || HasImplicitConversion(right.Type, left.Type))
+                    if ((left.Type == typeof(object) || right.Type == typeof(object)) && _expressionHelper.TryConvertTypes(ref left, ref right))
+                    {
+                        // #937
+                    }
+                    else if (left.Type.IsAssignableFrom(right.Type) || HasImplicitConversion(right.Type, left.Type))
                     {
                         right = Expression.Convert(right, left.Type);
                     }
@@ -2551,7 +2555,7 @@ private bool TokenIsIdentifier(string id)
     {
         return _textParser.TokenIsIdentifier(id);
     }
-    
+
     private string GetIdentifier()
     {
         _textParser.ValidateToken(TokenId.Identifier, Res.IdentifierExpected);

src/System.Linq.Dynamic.Core/Parser/IExpressionHelper.cs

@@ -48,4 +48,9 @@ internal interface IExpressionHelper
     Expression GenerateDefaultExpression(Type type);
 
     Expression ConvertAnyArrayToObjectArray(Expression arrayExpression);
+
+    /// <summary>
+    /// If the types are different (and not null), try to convert the object type to other type.
+    /// </summary>
+    public bool TryConvertTypes(ref Expression left, ref Expression right);
 }

test/System.Linq.Dynamic.Core.Tests/QueryableTests.Where.cs

@@ -5,6 +5,8 @@
 using System.Linq.Dynamic.Core.Tests.Helpers.Entities;
 using System.Linq.Dynamic.Core.Tests.Helpers.Models;
 using System.Linq.Expressions;
+using System.Text;
+using Docker.DotNet.Models;
 using FluentAssertions;
 using Xunit;
 
@@ -326,6 +328,56 @@ public void Where_Dynamic_DateTimeConstructor_Issue662()
         result2.Should().HaveCount(1);
     }
 
+    // #937
+    [Theory]
+    [InlineData("NameCalculated == \"FooFoo\"", 1)]
+    [InlineData("\"FooFoo\" == NameCalculated", 1)]
+    [InlineData("NameCalculated == \"x\"", 0)]
+    [InlineData("NameCalculated != \"x\"", 2)]
+    [InlineData("NameCalculated <> \"x\"", 2)]
+    [InlineData("\"x\" == NameCalculated", 0)]
+    [InlineData("\"x\" != NameCalculated", 2)]
+    [InlineData("\"x\" <> NameCalculated", 2)]
+    public void Where_Dynamic_CompareObjectToString_ConvertObjectToSupportComparisonIsTrue(string expression, int expectedCount)
+    {
+        // Arrange
+        var config = new ParsingConfig
+        {
+            ConvertObjectToSupportComparison = true
+        };
+        var queryable = new[]
+        {
+            new PersonWithObject { Name = "Foo", DateOfBirth = DateTime.UtcNow.AddYears(-31) },
+            new PersonWithObject { Name = "Bar", DateOfBirth = DateTime.UtcNow.AddYears(-1) }
+        }.AsQueryable();
+
+        // Act
+        queryable.Where(config, expression).ToList().Should().HaveCount(expectedCount);
+    }
+
+    // #937
+    [Theory]
+    [InlineData("NameCalculated == \"FooFoo\"", 0)] // This is the expected behavior when ConvertObjectToSupportComparison is false because "Foo" is a string and NameCalculated is an object which is a calculated string.
+    [InlineData("\"FooFoo\" == NameCalculated", 0)] // Also expected.
+    [InlineData("NameCalculated == \"x\"", 0)]
+    [InlineData("NameCalculated != \"x\"", 2)]
+    [InlineData("NameCalculated <> \"x\"", 2)]
+    [InlineData("\"x\" == NameCalculated", 0)]
+    [InlineData("\"x\" != NameCalculated", 2)]
+    [InlineData("\"x\" <> NameCalculated", 2)]
+    public void Where_Dynamic_CompareObjectToString_ConvertObjectToSupportComparisonIsFalse(string expression, int expectedCount)
+    {
+        // Arrange
+        var queryable = new[]
+        {
+            new PersonWithObject { Name = "Foo", DateOfBirth = DateTime.UtcNow.AddYears(-31) },
+            new PersonWithObject { Name = "Bar", DateOfBirth = DateTime.UtcNow.AddYears(-1) }
+        }.AsQueryable();
+
+        // Act
+        queryable.Where(expression).ToList().Should().HaveCount(expectedCount);
+    }
+
     // #451
     [Theory]
     [InlineData("Age == 99", 0)]
@@ -448,7 +500,11 @@ private class PersonWithObject
     {
         // Deliberately typing these as `object` to illustrate the issue
         public object? Name { get; set; }
+
+        public object? NameCalculated => Name + Encoding.ASCII.GetString(Convert.FromBase64String("Rm9v")); // "...Foo";
+
         public object Age => Convert.ToInt32(Math.Floor((DateTime.Today.Month - DateOfBirth.Month + 12 * DateTime.Today.Year - 12 * DateOfBirth.Year) / 12d));
+
         public DateTime DateOfBirth { get; set; }
     }