`FileLoadException: Assembly with same name is already loaded` when multiple Fody-using projects are referenced about fody

[andrewlock]

Currently, there's a separate load context for each solution directory, so maybe that could be a brittle approach? Note that when you're not using a solution, the project's parent directory is assumed to be the solution directory.

I think this could explain the issue then, both of these projects are in the same solution directory in our case 🙂 And they're also in the same parent directory

[ltrzesniewski]

My guess would be that you didn't put the PrivateAssets="All" attribute on all the Fody and InlineIL.Fody PackageReference items, could you check that?

Datadog.Trace.Runner shouldn't be trying to run Fody at all.

[andrewlock]

(Un) fortunately I checked that already.

Datadog.Trace has this:

<PackageReference Include="Fody" Version="6.8.0">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
<PackageReference Include="InlineIL.Fody" Version="1.8.0" PrivateAssets="All" />

and Datadog.Trace.Coverage.Collector has the same (with the now-updated InlineIL.Fody version):

<PackageReference Include="Fody" Version="6.8.0">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
<PackageReference Include="InlineIL.Fody" Version="1.8.0" PrivateAssets="All" />

[ltrzesniewski]

Well, that would have been an easy explanation. In any case, Fody is trying to load two different versions of InlineIL I suppose, and that doesn't go very well.

The build log you posted seems to show the failure happens while building Datadog.Trace.Coverage.collector though, which may indeed point to an issue caused by node reuse.

While we probably should improve the error message, understanding the issue would be useful, since the assembly is loaded in a separate AssemblyLoadContext in order to avoid such problems in the first place... 😕

Currently, there's a separate load context for each solution directory, so maybe that could be a brittle approach? Note that when you're not using a solution, the project's parent directory is assumed to be the solution directory.