Issue: Using escaped strings is not working correctly

[hypetsch]

In issue #65 some issues regarding the usage of escaped strings have been fixed. I am currently facing another issue in combination with escaped characters (backslashes and quotation marks).
TextParser.cs seems to not handle those scenarios correctly.
I have been able to reproduce the issue in unit tests:

[Fact]
public void ParseLambda_StringLiteral_Backslash()
{
    string expectedLeftValue = "Property1.IndexOf(\"\\\")";
    string expectedRightValue = "0";
    var expression = DynamicExpressionParser.ParseLambda(
        new[] { Expression.Parameter(typeof(string), "Property1") },
        typeof(Boolean),
        string.Format("{0} >= {1}", expectedLeftValue, expectedRightValue));

    string leftValue = ((BinaryExpression)expression.Body).Left.ToString();
    string rightValue = ((BinaryExpression)expression.Body).Right.ToString();
    Assert.Equal(typeof(Boolean), expression.Body.Type);
    Assert.Equal(expectedLeftValue, leftValue);
    Assert.Equal(expectedRightValue, rightValue);
}

[Fact]
public void ParseLambda_StringLiteral_QuotationMark()
{
    string expectedLeftValue = "Property1.IndexOf(\"\\\"\")";
    string expectedRightValue = "0";
    var expression = DynamicExpressionParser.ParseLambda(
        new[] { Expression.Parameter(typeof(string), "Property1") },
        typeof(Boolean),
        string.Format("{0} >= {1}", expectedLeftValue, expectedRightValue));

    string leftValue = ((BinaryExpression)expression.Body).Left.ToString();
    string rightValue = ((BinaryExpression)expression.Body).Right.ToString();
    Assert.Equal(typeof(Boolean), expression.Body.Type);
    Assert.Equal(expectedLeftValue, leftValue);
    Assert.Equal(expectedRightValue, rightValue);
}

I think the issue is that the current implementation assumes that it is always a full string (starting and ending with an escaped quotation mark) and not only a single escaped character.

Edit: Updated unit tests code

[ghost]

Hey, I got this issue again but only for backslashes, when switching from the NuGet package

wilx.System.Linq.Dynamic.Core 

(https://www.nuget.org/packages/wilx.System.Linq.Dynamic.Core/)
to

System.Linq.Dynamic.Core (Version 1.0.12)

I think the later one should be used?

Error:

System.Linq.Dynamic.Core.Exceptions.ParseException: 'Unterminated string literal'

Console app code to reproduce:

using System;
using System.Linq;
using System.Linq.Dynamic.Core;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            var strings = new[] { "test \\ string" }.AsQueryable();

            var count = strings.Count("ToString().Contains('\\')");
            //var count = strings.Count(s => s.ToString().Contains('\\'));

            Console.WriteLine("Elements found (should be 1): " + count);
            Console.ReadKey();
        }
    }
}

[StefH]

As a workaround you can use:
var count = strings.Count("Contains(@0)", "\\");

[ghost]

Thank you for the answer, this worked for me in the given example. At a different point we use an input string to filter out elements, so it would be quite complicated to get it to work that way, having multiple inputs for each argument in the string predicate, as well as that filter string containing the arguments.

Is there a plan to fix this in the future?

Thank you for your help!

[StefH]

I see your point, it seems that the parsing code in this library is different regarding escaping. I'll take a look if I can find and fix the logic.

[StefH]

@hypetsch and @SolidWhiteSven
I've changed the code, please try version 1.0.13-ci-11242 from MyGet.

https://www.myget.org/feed/system-linq-dynamic-core/package/nuget/System.Linq.Dynamic.Core

[ghost]

Hey @StefH, I've added the prerelease package with version 1.0.13-ci-11244 to the solution, but sadly I still get the 'Unterminated string literal' exception. I also thought the changes were only in the mentioned 11242 version, but that one also throws the error for this code:

using System;
using System.Linq;
using System.Linq.Dynamic.Core;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            var strings = new[] { "test \\ string" }.AsQueryable();

            var count = strings.Count("Contains('\\')");

            Console.WriteLine("Elements found (should be 1): " + count);
            Console.ReadKey();
        }
    }
}

[StefH]

You are correct, this test does not work. I've to double check the code again...

[StefH]

@SolidWhiteSven
Can you try 1.0.13-ci-11260 ?

[ghost]

@StefH Works like a charm, thank you!

[StefH]

@hypetsch Can you also do some tests please?

[hypetsch]

@StefH, thanks for your work. Just did a quick test: the test case ParseLambda_StringLiteral_Backslash() I added in the first comment still fails with a ParseException ('Unterminated string literal'). Think the test itself should be ok?

[StefH]

@hypetsch
Yes I noticed that also, so I changed the unit-test to be :

string expectedLeftValue = "Property1.IndexOf(\"\\\\\")";

Which means (to my knowledge):

• \" --> escape the double quote (start)
• \\\\ --> define a backslash : because the backslash is inside the double quotes, you need to escape it twice. If you just use \\, this will be translated to \ which is not valid because this is an escape character (https://devblogs.microsoft.com/csharpfaq/what-character-escape-sequences-are-available/) So we need to double escape the backslash
• \" --> escape the double quote (end)

[hypetsch]

Sorry, think you are right.
Some other tests I did meanwhile worked well. Thanks.

[StefH]

Thank you both for your help !

I will close this issue and merge the PR; in some time, I'll create a new official NuGet.