Found problem with backslashes parsing

[seregvan]

You closed my previous issue as a question so I'm opening a new one.
I think I found the problem in your parsing. I can't see the reason to do this in string literal parsing except the case when I try to find " in the result.

if (next == '"')
{
     NextChar();
}

Because if I use query "contains(\"\\\")" it fails with unterminated literal, but if I change query to "contains(\"\\a\")" it works finding "\a" string. And also if I use "contains(\"\\\\\")" it works with string "\\" (string with two real slashes).

So I think the correct solution will be to remove this if statement and just replace \" to " in the result token if it was a string literal. In this case if user will want to put " in query string it should be escaped inside this string. At least it will not break any existing code.
The better approach will be (in my opinion) to escape all the characters in the string by user and to unescape by parser. That means \\\\ will evaluate to \ and not to \\.
I understand your workaround by using @0 but it's not the case when search string comes outside my app.

[alexweav]

Hello @StefH, I just ran into this issue as well. The filter foo = "\"asdf\"" seems to match the literal including backslashes, and the filter foo = """asdf""", which is the literal format documented on the wiki, causes a parse failure.

Are there any workaround for parsing a dynamic linq lambda which contains a quote, other than substitutions? If not, would you please be able to point me towards this area in the code? I might be able to provide a PR, with some guidance.

[StefH]

@alexweav The parsing code is located here:

• https://github.com/StefH/System.Linq.Dynamic.Core/blob/master/src/System.Linq.Dynamic.Core/Tokenizer/TextParser.cs#L274
• https://github.com/StefH/System.Linq.Dynamic.Core/blob/8d8ecf9c2340f4518dc377e9fe7a6767dd71e392/src/System.Linq.Dynamic.Core/Parser/ExpressionParser.cs#L781

And some unit tests are defined here:

• https://github.com/StefH/System.Linq.Dynamic.Core/blob/8d8ecf9c2340f4518dc377e9fe7a6767dd71e392/src/System.Linq.Dynamic.Core/Parser/ExpressionParser.cs#L781-L726
• https://github.com/StefH/System.Linq.Dynamic.Core/blob/99aacdd95f60bbb859a6799ab1d0d6412d264762/test/System.Linq.Dynamic.Core.Tests/Tokenizer/TextParserTests.cs#L207

[alexweav]

@StefH I was able to work around this by running an ExpressionVisitor on the parsed lambda which simply calls Regex.Unescape() on all string constants. I wonder if something this simple would solve this issue? It ensures that all escape sequences inside string literals are parsed as escape sequences, not the literal characters. Do you think this is too drastic to apply everywhere?

The regex unescaping ensures that the expression Foo = "ab\"cd" returns true where Foo equals the string ab"cd. Without it, it will only return true where Foo equals ab\"cd with the backslash included.

[StefH]

Please make a PullRequest with unit tests or a new sample project.

[alexweav]

Test: #325

[StefH]

@alexweav and @seregvan Can you please test if version System.Linq.Dynamic.Core.1.0.20-ci-12219.nupkg from MyGet solves your issue?

[StefH]

@hypetsch and @SolidWhiteSven : you also where involved in string parsing issues, can you also verify if this fix is also in line with your usage?

Hey, I've updated to 1.0.20-ci-12230 and all my tests were successful.
Thanks by the was for keeping this package nice and updated :-)

[StefH]

@SolidWhiteSven The version you mention is a different one, you need System.Linq.Dynamic.Core.1.0.20-ci-12219.

Ah, I see, thought the changes were also included there.
Retested with version 12219 and it all still works as expected.

[StefH]

Closing as solved in PR #326