.NET Core

During the process of moving a Scala-based API to .NET Core, we encountered an interesting localization issue when running our code in a docker container based on an alpine image. The code itself was doing a currency formatting based on some culture. It looked more or less as below

[Route("api/[controller]")]
[ApiController]
public class PriceController : ControllerBase
{
    [HttpGet]
    public ActionResult<object> Get(string cultureCode = "de-DE")
    {
        var cultureInfo = CultureInfo.CreateSpecificCulture(cultureCode);
        var price = 10m;
        
        return new
        {
            price,
            formattedPrice = price.ToString("C", cultureInfo),
            currencySymbol = cultureInfo.NumberFormat.CurrencySymbol
        };
    }
}

[Route("api/[controller]")]

[ApiController]

public class PriceController : ControllerBase

{

[HttpGet]

public ActionResult<object> Get(string cultureCode = "de-DE")

{

var cultureInfo = CultureInfo.CreateSpecificCulture(cultureCode);

var price = 10m;

return new

{

price,

formattedPrice = price.ToString("C", cultureInfo),

currencySymbol = cultureInfo.NumberFormat.CurrencySymbol

};

}

We also had some integration tests for that piece of logic

public class PriceTests : IClassFixture<WebApplicationFactory<Startup>>
{
    private readonly WebApplicationFactory<Startup> _factory;

    public PriceTests(WebApplicationFactory<Startup> factory)
    {
        _factory = factory;
    }
        
    [Fact]
    public async Task GetPrice_ReturnsCorrectCurrency()
    {
        var httpClient = _factory.CreateClient();
        var httpResponseMessage = await httpClient.GetAsync("api/Price");
            
        httpResponseMessage.EnsureSuccessStatusCode();
        var content = await httpResponseMessage.Content.ReadAsStringAsync();
        var jObject = JObject.Parse(content);

        jObject["currencySymbol"].ToObject<string>().Should().Be("€");
    }
}

public class PriceTests : IClassFixture<WebApplicationFactory<Startup>>

{

private readonly WebApplicationFactory<Startup> _factory;

public PriceTests(WebApplicationFactory<Startup> factory)

{

_factory = factory;

}

[Fact]

public async Task GetPrice_ReturnsCorrectCurrency()

{

var httpClient = _factory.CreateClient();

var httpResponseMessage = await httpClient.GetAsync("api/Price");

httpResponseMessage.EnsureSuccessStatusCode();

var content = await httpResponseMessage.Content.ReadAsStringAsync();

var jObject = JObject.Parse(content);

jObject["currencySymbol"].ToObject<string>().Should().Be("€");

}

The tests were run during a CI build in a container with an image defined as below

# Builder image
FROM mcr.microsoft.com/dotnet/core/sdk:2.1.700-alpine AS builder
WORKDIR /sln

COPY ./*.sln ./

# Copy the main source project files
COPY src/*/*.csproj ./
RUN for file in $(ls *.csproj); do mkdir -p src/${file%.*}/ && mv $file src/${file%.*}/; done

# Copy the test project files
COPY test/*/*.csproj ./
RUN for file in $(ls *.csproj); do mkdir -p test/${file%.*}/ && mv $file test/${file%.*}/; done

RUN dotnet restore

# Copy across the rest of the source files
COPY ./test ./test
COPY ./src ./src

RUN dotnet build -c Release

RUN dotnet test "./test/AlpineMissingCurrencySymbol.Tests/AlpineMissingCurrencySymbol.Tests.csproj" \
    -c Release --no-build --no-restore

RUN dotnet publish "./src/AlpineMissingCurrencySymbol/AlpineMissingCurrencySymbol.csproj" \
    -c Release -o "../../dist" --no-restore

# App image
FROM mcr.microsoft.com/dotnet/core/aspnet:2.1.11-alpine
WORKDIR /app
ENTRYPOINT ["dotnet", "AlpineMissingCurrencySymbol.dll"]
COPY --from=builder /sln/dist .

# Builder image

FROM mcr.microsoft.com/dotnet/core/sdk:2.1.700-alpine AS builder

WORKDIR /sln

COPY ./*.sln ./

# Copy the main source project files

COPY src/*/*.csproj ./

RUN for file in $(ls *.csproj); do mkdir -p src/${file%.*}/ && mv $file src/${file%.*}/; done

# Copy the test project files

COPY test/*/*.csproj ./

RUN for file in $(ls *.csproj); do mkdir -p test/${file%.*}/ && mv $file test/${file%.*}/; done

RUN dotnet restore

# Copy across the rest of the source files

COPY ./test ./test

COPY ./src ./src

RUN dotnet build -c Release

RUN dotnet test "./test/AlpineMissingCurrencySymbol.Tests/AlpineMissingCurrencySymbol.Tests.csproj" \

-c Release --no-build --no-restore

RUN dotnet publish "./src/AlpineMissingCurrencySymbol/AlpineMissingCurrencySymbol.csproj" \

-c Release -o "../../dist" --no-restore

# App image

FROM mcr.microsoft.com/dotnet/core/aspnet:2.1.11-alpine

WORKDIR /app

ENTRYPOINT ["dotnet", "AlpineMissingCurrencySymbol.dll"]

COPY --from=builder /sln/dist .

At this point, we were sure that everything works fine, as the tests were green and everything was also working correctly on our local machines. However, after deployment to a testing environment, we started getting invalid currency symbols

curl localhost:8080/api/price 
{ 
  "price": 10, 
  "formattedPrice": "¤10.00", 
  "currencySymbol": "¤" 
}

curl localhost:8080/api/price

{

"price": 10,

"formattedPrice": "¤10.00",

"currencySymbol": "¤"

}

As you can see the response contains ¤ (invariant currency symbol) instead of expected €. It took us some time to figure this out but finally, it turned out that aspnet:2.1.11-alpine image(the one we used for running the application) contrary to the SDK image(used for building and running tests) is missing icu-libs package. In default conditions, the application should throw the following exception during the startup

FailFast:
Couldn't find a valid ICU package installed on the system. Set the configuration flag System.Globalization.Invariant to true if you want to run with no globalization support.

   at System.Environment.FailFast(System.String)
   at System.Globalization.GlobalizationMode.GetGlobalizationInvariantMode()
   at System.Globalization.GlobalizationMode..cctor()
   at System.Globalization.CultureData.CreateCultureWithInvariantData()
   at System.Globalization.CultureData.get_Invariant()
   at System.Globalization.CultureInfo..cctor()
   at System.StringComparer..cctor()
   at System.AppDomain.InitializeCompatibilityFlags()
   at System.AppDomain.Setup(System.Object)

FailFast:

Couldn't find a valid ICU package installed on the system. Set the configuration flag System.Globalization.Invariant to true if you want to run with no globalization support.

at System.Environment.FailFast(System.String)

at System.Globalization.GlobalizationMode.GetGlobalizationInvariantMode()

at System.Globalization.GlobalizationMode..cctor()

at System.Globalization.CultureData.CreateCultureWithInvariantData()

at System.Globalization.CultureData.get_Invariant()

at System.Globalization.CultureInfo..cctor()

at System.StringComparer..cctor()

at System.AppDomain.InitializeCompatibilityFlags()

at System.AppDomain.Setup(System.Object)

However, aspnet:2.1.11-alpine image has the DOTNET_SYSTEM_GLOBALIZATION_INVARIANT flag set to true by default, so the missing package was not validated during a startup. After all, in order to fix the issue, we had to install the icu-libs package and also set the DOTNET_SYSTEM_GLOBALIZATION_INVARIANT back to false. This was done by these two lines in Dockerfile

ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=false 
RUN apk add --no-cache icu-libs

1 2	ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=false RUN apk add --no-cache icu-libs

Once the lines were added the application started working as expected

curl localhost:8080/api/price 
{ 
  "price": 10, 
  "formattedPrice": "10,00 €", 
  "currencySymbol": "€" 
}

curl localhost:8080/api/price

{

"price": 10,

"formattedPrice": "10,00 €",

"currencySymbol": "€"

}

Source code for this post can be found here

1. Introduction.

I’ve been struggling for some time to make OpenCover work with .NET Core projects, so I’ve decided to document a working example. This is basically an aggregation of hints and answers I found on the Web (especially in here)

2. Working example.

If you run an OpenCover with the same arguments you were running it for a classic framework, you will end up with something like this
As you can see the coverage was not calculated and OpenCover is complaining about a missing PDBs. In order to fix that we have to do two things. First of all, we have to build the project with a full PDBs

dotnet build "PathToYourSolution.sln" /p:DebugType=Full

1	dotnet build "PathToYourSolution.sln" /p:DebugType=Full

And then run OpenCover with and -oldStyle switch

OpenCover.Console.exe -target:"C:/Program Files/dotnet/dotnet.exe" -targetargs:"test \"PathToTestProject.csproj\" --configuration Debug --no-build" -filter:"+[*]* -[*.Tests*]*" -oldStyle -register:user -output:"OpenCover.xml"

1	OpenCover.Console.exe -target:"C:/Program Files/dotnet/dotnet.exe" -targetargs:"test \"PathToTestProject.csproj\" --configuration Debug --no-build" -filter:"+[] -[.Tests]*" -oldStyle -register:user -output:"OpenCover.xml"

From now on, OpenCover recognizes PDB files and the code coverage is calculated correctly

3. Cake script.

As we use a Cake as our build automation tool I’ve also prepared a sample script for generating a code coverage. The core part of the script looks as follows

// rest of the code omitted for brevity

Task("Build")
    .IsDependentOn("Restore-NuGet-Packages")
    .Does(() =>
{
    DotNetCoreBuild(paths.Files.Solution.ToString(), new DotNetCoreBuildSettings
    {
        Configuration = parameters.Configuration,
        ArgumentCustomization = arg => arg.AppendSwitch("/p:DebugType","=","Full")
    });
});

Task("Run-Tests")
    .IsDependentOn("Build")
    .Does(() =>
{
    var success = true;
    var openCoverSettings = new OpenCoverSettings
    {
        OldStyle = true,
        MergeOutput = true
    }
    .WithFilter("+[*]* -[*.Tests*]*");

    foreach(var project in paths.Files.TestProjects)
    {
        try 
        {
            var projectFile = MakeAbsolute(project).ToString();
            var dotNetTestSettings = new DotNetCoreTestSettings
            {
                Configuration = parameters.Configuration,
                NoBuild = true
            };

            OpenCover(context => context.DotNetCoreTest(projectFile, dotNetTestSettings), paths.Files.TestCoverageOutput, openCoverSettings);
        }
        catch(Exception ex)
        {
            success = false;
            Error("There was an error while running the tests", ex);
        }
    }

    ReportGenerator(paths.Files.TestCoverageOutput, paths.Directories.TestResults);

    if(success == false)
    {
        throw new CakeException("There was an error while running the tests");
    }

});

// rest of the code omitted for brevity

Task("Build")

.IsDependentOn("Restore-NuGet-Packages")

.Does(() =>

{

DotNetCoreBuild(paths.Files.Solution.ToString(), new DotNetCoreBuildSettings

{

Configuration = parameters.Configuration,

ArgumentCustomization = arg => arg.AppendSwitch("/p:DebugType","=","Full")

});

Task("Run-Tests")

.IsDependentOn("Build")

.Does(() =>

{

var success = true;

var openCoverSettings = new OpenCoverSettings

{

OldStyle = true,

MergeOutput = true

}

.WithFilter("+[*]* -[*.Tests*]*");

foreach(var project in paths.Files.TestProjects)

{

try

{

var projectFile = MakeAbsolute(project).ToString();

var dotNetTestSettings = new DotNetCoreTestSettings

{

Configuration = parameters.Configuration,

NoBuild = true

};

OpenCover(context => context.DotNetCoreTest(projectFile, dotNetTestSettings), paths.Files.TestCoverageOutput, openCoverSettings);

}

catch(Exception ex)

{

success = false;

Error("There was an error while running the tests", ex);

}

ReportGenerator(paths.Files.TestCoverageOutput, paths.Directories.TestResults);

if(success == false)

{

throw new CakeException("There was an error while running the tests");

}

});

Notice that script is able to merge code coverage results from multiple test projects thanks to MergeOutput flag passed to OpenCover.

Full sources of that script (along with a dotnet vstest alternative approach) can be found here.

.NET BLOG

.NET, C# blog

.NET Core – missing currency symbol in docker alpine image

.NET Core – calculating code coverage with OpenCover (on Windows)

1. Introduction.

2. Working example.

3. Cake script.