AltCover.Prepare copies wrong FSharp.Core into Output directory

[matthid]

I'm not quite sure why but our build started failing and I can basically pin it down to the AltCover.Prepare task copying a wrong FSharp.Core.dll into the output directory. This issue either appeared when updating packages or when changing the target framework from net461 to netcoreapp2.2

Basically we included AltCover like this (in a separate targets file we include):

  <Target Name="CollectExpectoCoverage" DependsOnTargets="Restore;BuildProject">
    <!-- Altcover fails if _Reports folder doesn't exist -->
    <MakeDir
          Directories="$(OutputPath)/_Reports"/>
    <ItemGroup>
        <InputDirectory Include="$(OutputPath)" />
        <FileFilter Include="OurCompany+" />
        <OutputDirectory Include="$(OutputPath)/__Saved$([System.DateTime]::UtcNow.ToString().Replace(':','-').Replace('/','-').Replace(' ','+'))" />
    </ItemGroup>
    <AltCover.Prepare
      InputDirectories="@(InputDirectory)"
      OutputDirectories="@(OutputDirectory)"
      FileFilter="@(FileFilter)"
      XmlReport="$(ProjectDir)coverage.xml"
      OpenCover="true"
      />
    <Delete Files="$(OutputPath)/FSharp.Core.dll" /><!-- Workaround this issue -->
    <Exec Command="dotnet run -c $(Configuration) -f $(TargetFramework) --no-build -- --summary" ContinueOnError="WarnAndContinue"/>
    <PropertyGroup>
      <DotNetRunHasFailed Condition=" '$(MSBuildLastTaskResult)' != 'true' ">true</DotNetRunHasFailed>
      <DotNetRunHasFailed Condition=" '$(MSBuildLastTaskResult)' == 'true' ">false</DotNetRunHasFailed>
    </PropertyGroup>
    <AltCover.Collect RecorderDirectory="$(OutputPath)" />
    <Error
            Text="previous dotnet run failed."
            Condition="'$(DotNetRunHasFailed)' == 'true'" />
  </Target>

and call it like this:

dotnet build -c Release /t:CollectExpectoCoverage 

Result (when you delete the Workaround line):

  Instrumenting files in C:\proj\MyCompany.TestProject\source\Server.Tests\bin\Release\netcoreapp2.2\
     => C:\proj\MyCompany.TestProject\source\Server.Tests\bin\Release\netcoreapp2.2\__Saved2019-08-26+16-18-46\MyCompany.TestProject.Server.dll
     => C:\proj\MyCompany.TestProject\source\Server.Tests\bin\Release\netcoreapp2.2\__Saved2019-08-26+16-18-46\MyCompany.TestProject.Server.Tests.dll

  Coverage Report: C:\proj\MyCompany.TestProject\source\Server.Tests\coverage.xml


      C:\proj\MyCompany.TestProject\source\Server.Tests\bin\Release\netcoreapp2.2\MyCompany.TestProject.Server.dll
                  <=  MyCompany.TestProject.Server, Version=0.0.1.0, Culture=neutral, PublicKeyToken=null
      C:\proj\MyCompany.TestProject\source\Server.Tests\bin\Release\netcoreapp2.2\MyCompany.TestProject.Server.Tests.dll
                  <=  MyCompany.TestProject.Server.Tests, Version=0.0.1.0, Culture=neutral, PublicKeyToken=null

  Unhandled Exception:
     Cannot print exception string because Exception.ToString() failed.
C:\proj\MyCompany.TestProject\source\Coverage.targets(27,5): warning MSB3073: The command "dotnet run -c Release -f netcoreapp2.2 --no-build -- --summary" exited with code -532462766. [C:\proj\MyCompany.TestProject\source\Server.Tests\MyCompany.TestProject.Server.Tests.fsproj]
C:\proj\MyCompany.TestProject\source\Coverage.targets(32,5): warning : A total of 0 visits recorded [C:\proj\MyCompany.TestProject\source\Server.Tests\MyCompany.TestProject.Server.Tests.fsproj]
  Coverage statistics flushing took 3.68 seconds
  Visited Classes 0 of 664 (0)
  Visited Methods 0 of 1074 (0)
  Visited Points 0 of 2616 (0)
  Visited Branches 0 of 1812 (0)

  ==== Alternative Results (includes all methods including those without corresponding source) ====
  Alternative Visited Classes 0 of 676 (0)
  Alternative Visited Methods 0 of 1242 (0)
C:\proj\MyCompany.TestProject\source\Coverage.targets(33,5): error : previous dotnet run failed. [C:\proj\MyCompany.TestProject\source\Server.Tests\MyCompany.TestProject.Server.Tests.fsproj]

Build FAILED.

Note: A regular "build" doesn't copy any FSharp.Core into the output directory, we have the nuget package 4.6.2 referenced and 4.5.0 is copied to the directory.

Note2: To Debug

  Unhandled Exception:
     Cannot print exception string because Exception.ToString() failed.

I run the project with the debugger in the above state and the issue is a regular exception about unable to find the correct assembly. The bad reporting is not related to AltCover (which I initially thought) but can be reproduced by just running dotnet run --no-build in the above state.

[SteveGilham]

I think I see the issue here -- the defensive copying of FSharp.Core is based on .net framework world thinking; there needs to be a check for whether any of the assemblies being instrumented already reference it out of the nuget cache.

Also, I need to fix the <!-- Altcover fails if _Reports folder doesn't exist -->

[matthid]

Let me know if you need additional info, currently I think this should be straightforward to reproduce but maybe not

Regarding the defensive copy: If it isn't there we shouldn't copy it and if it is there we should copy only the exact same version.
Also: If we decide to copy it - we should never copy a version older than the latest reference / error out in that situation.

[SteveGilham]

Pre-release build 6.0.703-pre available for testing. Should address both issues, the unnecessary copying of FSharp.Core, and the need to create the report directory in advance.

[matthid]

Wow that was fast :) Will probably take me a bit to test

[SteveGilham]

The change is in the new release, too.

[matthid]

Indeed it seems to solve the problem, thanks for the fast release!