Running coverlet global tool over dotnet build intermittently fails to open file when calculating coverage

In my project https://github.com/SharpGenTools/SharpGenTools I’ve recently switched to using Coverlet for my code-coverage instrumentation. I’ve been encountering an intermittent issue where the Coverlet global tool is unable to open the hits file since it is being used by another process.

This only happens when I’m using the Coverlet global tool to instrument my MSBuild tasks while running dotnet build.

Here’s the repro steps that I have:

1. Clone SharpGenTools
2. In Powershell run ./build ; ./test. That will build SharpGenTools and then run the tests. It will likely fail to build the outerloop tests because the process will be unable to access the hits file.

Alternatively, run the following commands from the cloned build:

./build
./build/deploy-test-packages Debug
./build/build-outerloop-native
dotnet restore ./SdkTests/SdkTests.sln
coverlet ".\SdkTests\RestoredPackages\sharpgentools.sdk\2.0.0-local\tools\netstandard1.3\SharpGenTools.Sdk.dll" -t "dotnet" -a "build ./SdkTests/SdkTests.sln /nodeReuse:false --no-restore" -f opencover -o ./artifacts/coverage/outerloop.xml --include-test-assembly --include-directory .\SdkTests\RestoredPackages\sharpgentools.sdk\2.0.0-local\tools\netstandard1.3

The last command will fail with the issue.

I can also privately send you a minidump reproing the issue if you want.

[StevenTCramer]

The process cannot access the file ‘C:\agent_work\6\s\test\TestApp.EndToEnd.Tests\bin\Debug\netcoreapp3.0\BlazorState.dll’ because it is being used by another process.

Still happens with the maxcpucount set to 1

If anyone cares to review… https://timewarpenterprises.visualstudio.com/Blazor-State/_build/results?buildId=593 without coverlet they all pass.

[MarcoRossignoli]

-m:1 forces sequential builds using only one core

some infos https://docs.microsoft.com/en-us/visualstudio/msbuild/building-multiple-projects-in-parallel-with-msbuild?view=vs-2019