Suspicious AppBaseCompilationAssemblyResolver behaviour

[MarcoRossignoli]

On coverlet there are some scenario where we need to manually search asm to pass to Cecil during instrumentation.
During some user issue analisys we found a strange behaviour for AppBaseCompilationAssemblyResolver that lead to a resolution issue.

This is the point coverlet-coverage/coverlet#655 (comment)

runtime/src/installer/managed/Microsoft.Extensions.DependencyModel/Resolution/AppBaseCompilationAssemblyResolver.cs

Lines 91 to 114 in 639122a

	foreach (var assembly in library.Assemblies)
	{
	bool resolved = false;
	var assemblyFile = Path.GetFileName(assembly);
	foreach (var directory in directories)
	{
	string fullName;
	if (ResolverUtils.TryResolveAssemblyFile(_fileSystem, directory, assemblyFile, out fullName))
	{
	paths.Add(fullName);
	resolved = true;
	break;
	}
	}
	if (!resolved)
	{
	return false;
	}
	}
	// only modify the assemblies parameter if we've resolved all files
	assemblies?.AddRange(paths);
	return true;

Is it correct that in case of empty Assemblies resolver return true but actually without add any path to assemblies list?

cc: @jhartmann123

[MarcoRossignoli]

Any news on this?

[eerhardt]

My understanding of the logic is that the method returns true if it resolved all the Assemblies in the CompilationLibrary. In this case there were no .Assemblies, so they all were resolved. The other resolvers that we provide behave that way. Here are the other 2:

runtime/src/installer/managed/Microsoft.Extensions.DependencyModel/Resolution/PackageCompilationAssemblyResolver.cs

Lines 109 to 125 in 4f9ae42

	foreach (var assembly in library.Assemblies)
	{
	string fullName;
	if (!ResolverUtils.TryResolveAssemblyFile(fileSystem, basePath, assembly, out fullName))
	{
	// if one of the files can't be found, skip this package path completely.
	// there are package paths that don't include all of the "ref" assemblies
	// (ex. ones created by 'dotnet store')
	results = null;
	return false;
	}
	paths.Add(fullName);
	}
	results = paths;
	return true;

runtime/src/installer/managed/Microsoft.Extensions.DependencyModel/Resolution/ReferenceAssemblyPathResolver.cs

Lines 47 to 56 in 4f9ae42

	foreach (var assembly in library.Assemblies)
	{
	string fullName;
	if (!TryResolveReferenceAssembly(assembly, out fullName))
	{
	throw new InvalidOperationException($"Cannot find reference assembly '{assembly}' file for package {library.Name}");
	}
	assemblies.Add(fullName);
	}
	return true;

If you want/need to handle this situation separately, I would advise injecting your own resolver to the beginning of the list when invoking CompilationLibrary.ResolveReferencePaths(params ICompilationAssemblyResolver[] customResolvers).

[eerhardt]

Note that if the resolvers didn’t have this behavior, an exception would be thrown any time this situation occurred.

runtime/src/installer/managed/Microsoft.Extensions.DependencyModel/CompilationLibrary.cs

Line 82 in 4f9ae42

throw new InvalidOperationException($"Cannot find compilation library location for package '{Name}'");

[MarcoRossignoli]

Understood thank you @eerhardt!