CoreLib's coverage measurement is broken

[ViktorHofer]

After figuring out why CoreLib doesn't write the result file when being instrumented by coverlet and working around the issue, I noticed that the WriteLog and WriteHits methods in the ModuleTrackerTemplate throw:

  Unhandled exception. System.TypeLoadException: Could not load type 'System.Diagnostics.Process' from assembly 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e'.
     at Coverlet.Core.Instrumentation.Tracker.System.Private.CoreLib_19e73ecb-b988-441a-913d-54373b41abc8.WriteLog(String)
     at Coverlet.Core.Instrumentation.Tracker.System.Private.CoreLib_19e73ecb-b988-441a-913d-54373b41abc8.UnloadModule(Object, EventArgs)
     at System.AppContext.OnProcessExit() in C:\git\runtime3\src\libraries\System.Private.CoreLib\src\System\AppContext.cs:line 88

• coverlet/src/coverlet.core/Instrumentation/ModuleTrackerTemplate.cs

  Line 176 in df968b8

  string logFile = Path.Combine(location.FullName, $"{Path.GetFileName(currentAssembly.Location)}_{DateTime.UtcNow.Ticks}_{Process.GetCurrentProcess().Id}.txt");

• coverlet/src/coverlet.core/Instrumentation/ModuleTrackerTemplate.cs

  Line 200 in df968b8

  File.AppendAllText(Path.Combine(Path.GetDirectoryName(location), Path.GetFileName(location) + "_tracker.txt"), $"[{DateTime.UtcNow} P:{Process.GetCurrentProcess().Id} T:{Thread.CurrentThread.ManagedThreadId}]{logText}{Environment.NewLine}");

That's because CoreLib doesn't have access to the Process type and even though those code paths aren't running by default, they are in the IL and hence the types are tried to be resolved. To unblock dotnet/runtime it would be great if these code paths that rely on Process could be changed to not include the process id.

cc @stephentoub

[ViktorHofer]

cc @MarcoRossignoli

[jkotas]

You can get process ID using Environment.ProcessId in recent .NET runtimes.

[MarcoRossignoli]

We instrument and after tests can run in different runtime(after in the workflow), so I don't think that we can use #ifdef here(we build/ship for netstandard2.0).

Anyway that id is used only to avoid filename clash and are used for debugging purpose, so to not complicate too much the code we can substitute with a Guid. Is it available on CoreLib?

[stephentoub]

we can substitute with a Guid. Is it available on CoreLib?

yes

[MarcoRossignoli]

We'll ship nightly build at midnight, would be great is someone tomorrow give it a try to check if this first issue is solved https://github.com/coverlet-coverage/coverlet/blob/master/Documentation/ConsumeNightlyBuild.md

[stephentoub]

Thank you for working on the fixes, @MarcoRossignoli.