Coverlet doesn't track coverage of method with a LINQ query in an if statement

[Shkeeny]

When a method has a LINQ query in an if :

 public async Task<IAccessResponse> CreateAsync(DocumentEntity entity)
            {
            var list = new List<DocumentEntity> { new DocumentEntity { id = "1" }, new DocumentEntity { id = "2" } };

            if (list.Count(l => l.id == "1") > 1)
                throw new Exception();

            return new AccessResponse();
            }

We get a result in the code coverage, that looks something like this:

But if we extract the query to a variable, it seems to work fine:

Seems like the issue is reproducible in coverlet.msbuild versions 2.7.0 and 2.8.0.
Version 2.6.3 works fine.

[MarcoRossignoli]

Possible dup of #730
Can you try with our nightly build to understand if bug was fixed? https://github.com/tonerdo/coverlet/blob/master/Documentation/ConsumeNightlyBuild.md

[Shkeeny]

Tried on version 2.8.38-g34d6dc5ff6, still the same issue.

[MarcoRossignoli]

Debug or Release config?

[MarcoRossignoli]

cc: @matteoerigozzi 👀

[jutrera]

Hi Marco.

The issue is happening with Linq in some different ways. I will show some pictures with different code for the same method. Hope it helps.

First approach fails

Remove Any() instead of Count() -> Fails

Remove Linq expression instead a for loop -> Runs

Remove Any and/or Count expressions instead of FirstOrDefault -> Fails

Extracting from a method -> Runs

[MarcoRossignoli]

Can someone provide a repro project?

[petli]

I've run into something similar, and have a repro project here that also shows it to be an issue with foreach:
https://github.com/petli/coverlet-issue-760-demo/blob/master/Demo/Demo/Implementation.cs

Coverage:
https://github.com/petli/coverlet-issue-760-demo/blob/master/coverage.cobertura.xml

It seems to be the combination of IEnumerable<> and the async state engine that causes coverlet to ignore all lines except the if/foreach line.

[cdjc]

Zip file attached, but in short, to repro, you can create the example webapi app:
$ dotnet new webapi
And then add these methods to WeatherForecastController.cs:
(The second method has the test pulled out of the if statement)

        [HttpGet]
        public async Task<IActionResult> Not_Seen_By_Coverage() // except the lambdas
        {
            var rng = new Random();
            var rval = Enumerable.Range(1, 5).Select(index => new WeatherForecast  // lambda is seen by coverage
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = rng.Next(-20, 55),
                Summary = Summaries[rng.Next(Summaries.Length)]
            })
            .ToArray();
            await Task.Delay(100);
            var sumList = Summaries.ToList();
            if (sumList.Any(s => 0 >= 3))  // lambda is seen by coverage
            {
                return StatusCode(400);
            }
            return StatusCode(500);
        }

        [HttpGet]
        public async Task<IActionResult> Seen_By_Coverage()
        {
            var rng = new Random();
            var rval = Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = rng.Next(-20, 55),
                Summary = Summaries[rng.Next(Summaries.Length)]
            })
            .ToArray();
            await Task.Delay(100);
            var sumList = Summaries.ToList();
            var foo = sumList.Any(s => 0 >= 3);
            if (foo)
            {
                return StatusCode(400);
            }
            return StatusCode(500);
        }

example_issue_760.zip

[MarcoRossignoli]

thanks guys I'll take a look asap!