Fix to #23472 - !boolean in query should convert to boolean == false …

…rather than boolean != true where possible

When comparing something to bool constant, which is later negated we now flip the constant true -> false and false -> true, rather than flipping the operation from == to !=

src/EFCore.Relational/Query/SqlNullabilityProcessor.cs

@@ -1490,6 +1490,34 @@ private SqlExpression OptimizeNonNullableNotExpression(SqlUnaryExpression sqlUna
                                 sqlBinaryOperand.TypeMapping)!);
                     }
 
+                    // use equality where possible
+                    // !(a == true) -> a == false
+                    // !(a == false) -> a == true
+                    // !(true == a) -> false == a
+                    // !(false == a) -> true == a
+                    if (sqlBinaryOperand.OperatorType == ExpressionType.Equal)
+                    {
+                        if (sqlBinaryOperand.Left is SqlConstantExpression leftConstant
+                            && leftConstant.Type == typeof(bool))
+                        {
+                            return _sqlExpressionFactory.MakeBinary(
+                                ExpressionType.Equal,
+                                _sqlExpressionFactory.Constant(!(bool)leftConstant.Value!, leftConstant.TypeMapping),
+                                sqlBinaryOperand.Right,
+                                sqlBinaryOperand.TypeMapping)!;
+                        }
+
+                        if (sqlBinaryOperand.Right is SqlConstantExpression rightConstant
+                            && rightConstant.Type == typeof(bool))
+                        {
+                            return _sqlExpressionFactory.MakeBinary(
+                                ExpressionType.Equal,
+                                sqlBinaryOperand.Left,
+                                _sqlExpressionFactory.Constant(!(bool)rightConstant.Value!, rightConstant.TypeMapping),
+                                sqlBinaryOperand.TypeMapping)!;
+                        }
+                    }
+
                     // !(a == b) -> a != b
                     // !(a != b) -> a == b
                     // !(a > b) -> a <= b

src/EFCore.SqlServer/Query/Internal/SearchConditionConvertingExpressionVisitor.cs

@@ -74,22 +74,50 @@ private SqlExpression BuildCompareToExpression(SqlExpression sqlExpression)
                         sqlExpression,
                         _sqlExpressionFactory.Constant(true));
 
-        // !(a == b) -> (a != b)
-        // !(a != b) -> (a == b)
+
         private SqlExpression SimplifyNegatedBinary(SqlExpression sqlExpression)
-            => sqlExpression is SqlUnaryExpression sqlUnaryExpression
+        {
+            if (sqlExpression is SqlUnaryExpression sqlUnaryExpression
                 && sqlUnaryExpression.OperatorType == ExpressionType.Not
                 && sqlUnaryExpression.Type == typeof(bool)
                 && sqlUnaryExpression.Operand is SqlBinaryExpression sqlBinaryOperand
-                && (sqlBinaryOperand.OperatorType == ExpressionType.Equal || sqlBinaryOperand.OperatorType == ExpressionType.NotEqual)
-                    ? _sqlExpressionFactory.MakeBinary(
+                && (sqlBinaryOperand.OperatorType == ExpressionType.Equal || sqlBinaryOperand.OperatorType == ExpressionType.NotEqual))
+            {
+                if (sqlBinaryOperand.Left.Type == typeof(bool)
+                    && sqlBinaryOperand.Right.Type == typeof(bool)
+                    && (sqlBinaryOperand.Left is SqlConstantExpression
+                        || sqlBinaryOperand.Right is SqlConstantExpression))
+                {
+                    var constant = sqlBinaryOperand.Left as SqlConstantExpression ?? (SqlConstantExpression)sqlBinaryOperand.Right;
+                    if (sqlBinaryOperand.Left is SqlConstantExpression)
+                    {
+                        return _sqlExpressionFactory.MakeBinary(
+                            ExpressionType.Equal,
+                            _sqlExpressionFactory.Constant(!(bool)constant.Value!, constant.TypeMapping),
+                            sqlBinaryOperand.Right,
+                            sqlBinaryOperand.TypeMapping)!;
+                    }
+                    else
+                    {
+                        return _sqlExpressionFactory.MakeBinary(
+                            ExpressionType.Equal,
+                            sqlBinaryOperand.Left,
+                            _sqlExpressionFactory.Constant(!(bool)constant.Value!, constant.TypeMapping),
+                            sqlBinaryOperand.TypeMapping)!;
+                    }
+                }
+
+                return _sqlExpressionFactory.MakeBinary(
                         sqlBinaryOperand.OperatorType == ExpressionType.Equal
                             ? ExpressionType.NotEqual
                             : ExpressionType.Equal,
                         sqlBinaryOperand.Left,
                         sqlBinaryOperand.Right,
-                        sqlBinaryOperand.TypeMapping)!
-                    : sqlExpression;
+                        sqlBinaryOperand.TypeMapping)!;
+            }
+
+            return sqlExpression;
+        }
 
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to

test/EFCore.Cosmos.FunctionalTests/CustomConvertersCosmosTest.cs

@@ -112,6 +112,17 @@ FROM root c
 WHERE (c[""Discriminator""] IN (""Blog"", ""RssBlog"") AND (c[""IsVisible""] = ""Y""))");
         }
 
+        [ConditionalFact]
+        public override void Where_negated_bool_gets_converted_to_equality_when_value_conversion_is_used()
+        {
+            base.Where_negated_bool_gets_converted_to_equality_when_value_conversion_is_used();
+
+            AssertSql(
+                @"SELECT c
+FROM root c
+WHERE (c[""Discriminator""] IN (""Blog"", ""RssBlog"") AND NOT((c[""IsVisible""] = ""Y"")))");
+        }
+
         [ConditionalFact]
         public override void Where_bool_gets_converted_to_equality_when_value_conversion_is_used_using_EFProperty()
         {

test/EFCore.Specification.Tests/CustomConvertersTestBase.cs

@@ -488,6 +488,16 @@ public virtual void Where_bool_gets_converted_to_equality_when_value_conversion_
             Assert.Equal("http://blog.com", result.Url);
         }
 
+        [ConditionalFact]
+        public virtual void Where_negated_bool_gets_converted_to_equality_when_value_conversion_is_used()
+        {
+            using var context = CreateContext();
+            var query = context.Set<Blog>().Where(b => !b.IsVisible).ToList();
+
+            var result = Assert.Single(query);
+            Assert.Equal("http://rssblog.com", result.Url);
+        }
+
         [ConditionalFact]
         public virtual void Where_bool_with_value_conversion_inside_comparison_doesnt_get_converted_twice()
         {

test/EFCore.SqlServer.FunctionalTests/CustomConvertersSqlServerTest.cs

@@ -243,6 +243,17 @@ FROM [Blog] AS [b]
 WHERE [b].[IsVisible] = N'Y'");
         }
 
+        [ConditionalFact]
+        public override void Where_negated_bool_gets_converted_to_equality_when_value_conversion_is_used()
+        {
+            base.Where_negated_bool_gets_converted_to_equality_when_value_conversion_is_used();
+
+            AssertSql(
+                @"SELECT [b].[BlogId], [b].[Discriminator], [b].[IndexerVisible], [b].[IsVisible], [b].[Url], [b].[RssUrl]
+FROM [Blog] AS [b]
+WHERE [b].[IsVisible] = N'N'");
+        }
+
         public override void Where_bool_gets_converted_to_equality_when_value_conversion_is_used_using_EFProperty()
         {
             base.Where_bool_gets_converted_to_equality_when_value_conversion_is_used_using_EFProperty();
@@ -260,7 +271,7 @@ public override void Where_bool_gets_converted_to_equality_when_value_conversion
             AssertSql(
                 @"SELECT [b].[BlogId], [b].[Discriminator], [b].[IndexerVisible], [b].[IsVisible], [b].[Url], [b].[RssUrl]
 FROM [Blog] AS [b]
-WHERE [b].[IndexerVisible] <> N'Aye'");
+WHERE [b].[IndexerVisible] = N'Nay'");
         }
 
         public override void Object_to_string_conversion()