Source Generator generated files cause coverage generation error with source link + deterministic builds

This is an odd combination of a few things but it seems that you get the following error when the following combination of things happens:

The Problem

If you have a project that uses a source generator (The attached example uses Generator.Equals for equality checks), uses sourcelink and deterministic builds then when running

dotnet test --collect:“XPlat Code Coverage” --settings “.\coverlet.runsettings”

you get

Data collector 'XPlat code coverage' message: [coverlet]Coverlet.Collector.Utilities.CoverletDataCollectorException: CoverletCoverageDataCollector: Failed to get coverage result
 ---> System.Collections.Generic.KeyNotFoundException: The given key '' was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key) in System.Private.CoreLib.dll:token 0x600675e+0x17
   at Coverlet.Core.Coverage.GetSourceLinkUrl(Dictionary`2 sourceLinkDocuments, String document) in /_/src/coverlet.core/Coverage.cs:line 510
   at Coverlet.Core.Coverage.CalculateCoverage() in /_/src/coverlet.core/Coverage.cs:line 391
   at Coverlet.Core.Coverage.GetCoverageResult() in /_/src/coverlet.core/Coverage.cs:line 173
   at Coverlet.Collector.DataCollection.CoverageWrapper.GetCoverageResult(Coverage coverage) in /_/src/coverlet.collector/DataCollection/CoverageWrapper.cs:line 52
   at Coverlet.Collector.DataCollection.CoverageManager.GetCoverageResult() in /_/src/coverlet.collector/DataCollection/CoverageManager.cs:line 93
   --- End of inner exception stack trace ---
   at Coverlet.Collector.DataCollection.CoverageManager.GetCoverageResult() in /_/src/coverlet.collector/DataCollection/CoverageManager.cs:line 98
   at Coverlet.Collector.DataCollection.CoverletCoverageCollector.OnSessionEnd(Object sender, SessionEndEventArgs e) in /_/src/coverlet.collector/DataCollection/CoverletCoverageCollector.cs:line 161.

Workaround

The workaround is that you can add an ExcludeByFile for *.g.cs which stops them hitting this case although there’s obviously something unexpected happening.

Reproduction

CoverletRepoProject.zip

[sharwell]

Outputs from source generators are generally embedded in the PDB. Coverlet should always check the PDB for embedded source before checking for files on disk; when present, the embedded sources are always a more accurate source of truth than files on disk.

[sharwell]

But are non-generated source files embedded in the PDB too?

It can be configured either way. You should be able to check the source location for the specific file and still determine its origin.