Sqlite: Support translation of ToString

src/EFCore.Sqlite.Core/Query/Internal/SqliteMethodCallTranslatorProvider.cs

@@ -31,6 +31,7 @@ public SqliteMethodCallTranslatorProvider([NotNull] RelationalMethodCallTranslat
                     new SqliteByteArrayMethodTranslator(sqlExpressionFactory),
                     new SqliteDateTimeAddTranslator(sqlExpressionFactory),
                     new SqliteMathTranslator(sqlExpressionFactory),
+                    new SqliteObjectToStringTranslator(sqlExpressionFactory),
                     new SqliteStringMethodTranslator(sqlExpressionFactory)
                 });
         }

src/EFCore.Sqlite.Core/Query/Internal/SqliteObjectToStringTranslator.cs

@@ -0,0 +1,73 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Query;
+using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
+using Microsoft.EntityFrameworkCore.Utilities;
+
+namespace Microsoft.EntityFrameworkCore.Sqlite.Query.Internal
+{
+    /// <summary>
+    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+    ///     any release. You should only use it directly in your code with extreme caution and knowing that
+    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+    /// </summary>
+    public class SqliteObjectToStringTranslator : IMethodCallTranslator
+    {
+        private static readonly HashSet<Type> _typeMapping = new HashSet<Type>
+            {
+                typeof(int),
+                typeof(long),
+                typeof(Guid),
+                typeof(byte),
+                typeof(byte[]),
+                typeof(decimal),
+                typeof(double),
+                typeof(float),
+                typeof(char),
+                typeof(short),
+                typeof(DateTime),
+                typeof(DateTimeOffset),
+                typeof(TimeSpan),
+                typeof(uint),
+                typeof(ushort),
+                typeof(sbyte),
+                typeof(bool),
+            };
+
+        private readonly ISqlExpressionFactory _sqlExpressionFactory;
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        public SqliteObjectToStringTranslator([NotNull] ISqlExpressionFactory sqlExpressionFactory)
+            => _sqlExpressionFactory = sqlExpressionFactory;
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        public virtual SqlExpression Translate(SqlExpression instance, MethodInfo method, IReadOnlyList<SqlExpression> arguments)
+        {
+            Check.NotNull(method, nameof(method));
+            Check.NotNull(arguments, nameof(arguments));
+
+            return method.Name == nameof(ToString)
+                && arguments.Count == 0
+                && instance != null
+                && _typeMapping.Contains(instance.Type.UnwrapNullableType())
+                    ? _sqlExpressionFactory.Convert(instance, typeof(string))
+                    : null;
+        }
+    }
+}

test/EFCore.Sqlite.FunctionalTests/BuiltInDataTypesSqliteTest.cs

@@ -1500,7 +1500,7 @@ public override void Object_to_string_conversion()
             base.Object_to_string_conversion();
 
             AssertSql(
-                @"SELECT ""b"".""TestSignedByte"", ""b"".""TestByte"", ""b"".""TestInt16"", ""b"".""TestUnsignedInt16"", ""b"".""TestInt32"", ""b"".""TestUnsignedInt32"", ""b"".""TestInt64"", ""b"".""TestUnsignedInt64"", ""b"".""TestSingle"", ""b"".""TestDouble"", ""b"".""TestDecimal"", ""b"".""TestCharacter"", ""b"".""TestDateTime"", ""b"".""TestDateTimeOffset"", ""b"".""TestTimeSpan""
+                @"SELECT CAST(""b"".""TestSignedByte"" AS TEXT), CAST(""b"".""TestByte"" AS TEXT), CAST(""b"".""TestInt16"" AS TEXT), CAST(""b"".""TestUnsignedInt16"" AS TEXT), CAST(""b"".""TestInt32"" AS TEXT), CAST(""b"".""TestUnsignedInt32"" AS TEXT), CAST(""b"".""TestInt64"" AS TEXT), ""b"".""TestUnsignedInt64"", CAST(""b"".""TestSingle"" AS TEXT), CAST(""b"".""TestDouble"" AS TEXT), CAST(""b"".""TestDecimal"" AS TEXT), CAST(""b"".""TestCharacter"" AS TEXT), CAST(""b"".""TestDateTime"" AS TEXT), CAST(""b"".""TestDateTimeOffset"" AS TEXT), CAST(""b"".""TestTimeSpan"" AS TEXT)
 FROM ""BuiltInDataTypes"" AS ""b""
 WHERE ""b"".""Id"" = 13");
         }

test/EFCore.Sqlite.FunctionalTests/ConvertToProviderTypesSqliteTest.cs

@@ -17,6 +17,11 @@ public ConvertToProviderTypesSqliteTest(ConvertToProviderTypesSqliteFixture fixt
             //fixture.TestSqlLoggerFactory.SetTestOutputHelper(testOutputHelper);
         }
 
+        public override void Object_to_string_conversion()
+        {
+            // Return values are not string
+        }
+
         public class ConvertToProviderTypesSqliteFixture : ConvertToProviderTypesFixtureBase
         {
             public override bool StrictEquality

test/EFCore.Sqlite.FunctionalTests/CustomConvertersSqliteTest.cs

@@ -104,6 +104,11 @@ public override void Where_bool_gets_converted_to_equality_when_value_conversion
 WHERE ""b"".""IndexerVisible"" <> 'Aye'");
         }
 
+        public override void Object_to_string_conversion()
+        {
+            // Return values are not string
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
 

test/EFCore.Sqlite.FunctionalTests/Query/NorthwindMiscellaneousQuerySqliteTest.cs

@@ -25,8 +25,15 @@ public class NorthwindMiscellaneousQuerySqliteTest : NorthwindMiscellaneousQuery
             //Fixture.TestSqlLoggerFactory.SetTestOutputHelper(testOutputHelper);
         }
 
-        public override Task Query_expression_with_to_string_and_contains(bool async)
-            => AssertTranslationFailed(() => base.Query_expression_with_to_string_and_contains(async));
+        public override async Task Query_expression_with_to_string_and_contains(bool async)
+        {
+            await base.Query_expression_with_to_string_and_contains(async);
+
+            AssertSql(
+                @"SELECT ""o"".""CustomerID""
+FROM ""Orders"" AS ""o""
+WHERE ""o"".""OrderDate"" IS NOT NULL AND (('10' = '') OR (instr(CAST(""o"".""EmployeeID"" AS TEXT), '10') > 0))");
+        }
 
         public override async Task Take_Skip(bool async)
         {