0% coverage of library when using source generator

Hello,

I have a library targeted .Net Standard 2.0 and a test project using NUnit and targeted .Net 5.0. I used coverlet to calculate code-coverage as described in https://docs.microsoft.com/en-us/dotnet/core/testing/unit-testing-code-coverage?tabs=windows.

Recently I started to use ISourceGenerator to generate some files during build. After that I noticed that code coverage emits coverage.cobertura.xml file with the following content :

<?xml version="1.0" encoding="utf-8"?>
<coverage line-rate="0" branch-rate="0" version="1.9" timestamp="1638209313" lines-covered="0" lines-valid="0" branches-covered="0" branches-valid="0">
  <sources>
    <source></source>
  </sources>
  <packages />

I played much with coverlet.collector v3.1.0 and coverlet.msbuild v3.1.0 but always got an empty report (0 lines being covered). Here is an output of command :

# dotnet test --configuration Debug /p:CollectCoverage=true --diag:log.txt --settings runsettings.xml
  Determining projects to restore...
  All projects are up-to-date for restore.
  Assure.EnumsGenerator -> ../Assure.EnumsGenerator/bin/Debug/netstandard2.0/Assure.EnumsGenerator.dll
  Assure -> ../dotnet/Assure/bin/Debug/netstandard2.0/Assure.dll
  Assure.Tests -> ../Assure.Tests/bin/Debug/net5.0/Assure.Tests.dll
Test run for ../Assure.Tests/bin/Debug/net5.0/Assure.Tests.dll (.NETCoreApp,Version=v5.0)
Microsoft (R) Test Execution Command Line Tool Version 16.11.0
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
Logging Vstest Diagnostics in file: ../log.txt
A total of 1 test files matched the specified pattern.

Attachments:
  ../Assure.Tests/TestResults/777aab11-c4d4-45b7-9acf-639bc68fa0bd/coverage.info
  ../Assure.Tests/TestResults/777aab11-c4d4-45b7-9acf-639bc68fa0bd/coverage.cobertura.xml
Passed!  - Failed:     0, Passed:  2029, Skipped:     0, Total:  2029, Duration: 764 ms - ../Assure.Tests/bin/Debug/net5.0/Assure.Tests.dll (net5.0)

Calculating coverage result...
  Generating report ../Assure.Tests/coverage.json'

+--------+------+--------+--------+
| Module | Line | Branch | Method |
+--------+------+--------+--------+

+---------+------+--------+--------+
|         | Line | Branch | Method |
+---------+------+--------+--------+
| Total   | 0%   | 0%     | 0%     |
+---------+------+--------+--------+
| Average | 0%   | 0%     | 0%     |
+---------+------+--------+--------+

#

File log.datacollector.21-11-29_18-08-30_12299_4.txt keeps a message :

TpTrace Verbose: 0 : 21376, 1, 2021/11/29, 18:08:30.641, 90805477623404, datacollector.dll, [coverlet]Unable to instrument module: ../Assure.Tests/bin/Debug/net5.0/Assure.dll, pdb without local source files, [.../Assure/Assure.EnumsGenerator/Assure.EnumsGenerator.EnumsGenerator/AccessRight.cs]
TpTrace Verbose: 0 : 21376, 1, 2021/11/29, 18:08:30.695, 90805531432922, datacollector.dll, [coverlet]Unable to instrument module: .../Assure.Tests/bin/Debug/net5.0/Moq.dll, embedded pdb without local source files, [C:\projects\moq4\src\Moq\obj\TypeNameFormatter.cs]
TpTrace Information: 0 : 21376, 1, 2021/11/29, 18:08:30.734, 90805570278990, datacollector.dll, DataCollectionRequestHandler.ProcessRequests : DataCollection started.
TpTrace Information: 0 : 21376, 1, 2021/11/29, 18:08:30.765, 90805601531262, datacollector.dll, DataCollectionRequestHandler.ProcessRequests : Datacollector received message: (DataCollection.TestHostLaunched) -> {
  "ProcessId": 21394
}
TpTrace Information: 0 : 21376, 1, 2021/11/29, 18:08:33.808, 90808644847167, datacollector.dll, DataCollectionRequestHandler.ProcessRequests : Datacollector received message: (DataCollection.AfterTestRunEnd) -> false
TpTrace Verbose: 0 : 21376, 1, 2021/11/29, 18:08:33.809, 90808645919498, datacollector.dll, [coverlet]CoverletCoverageDataCollector: SessionEnd received

In log.host.21-11-29_18-08-30_74105_4.txt I noticed a bunch of messages like :

TpTrace Warning: 0 : 21394, 13, 2021/11/29, 18:08:31.922, 90806758548843, testhost.dll, TestRunCache: No test found corresponding to testResult 'CreateSubclasses(Assure.Common.ServerAlreadyActivatedError: [AlreadyExists] : ,AlreadyExists)' in inProgress list.

Could somebody please assist to understand what is wrong ? Also, coverlet works fine when I remove compile-time code-generation.

PS : runsettings.xml :

<?xml version="1.0" encoding="utf-8"?>

<RunSettings>
	<DataCollectionRunSettings>
		<DataCollectors>
			<DataCollector friendlyName="XPlat code coverage">
				<Configuration>
					<Format>lcov,cobertura</Format>
					<UseSourceLink>true</UseSourceLink>
					<Include>Assure.Client*</Include>
				</Configuration>
			</DataCollector>
		</DataCollectors>
	</DataCollectionRunSettings>
</RunSettings> 

[dimarusyy]

Thanks for help! Changing filename to .g.cs fixed the issue for me too.

[Andreas-Huber]

Ah sorry, I was already ahead and pushed a new commit after Peters comment with the .g.cs suffix - it was not there before. So that seems to fix it in the playground project. I was just about to test that in the production project because I thought adding the .g.cs suffix was one of the things I tried already.

So in this case adding .g.cs definitely fixed it.