public async Task <IReadOnlyList <NuGetVersion> > FindPackageVersionsOrNullAsync(
string id,
CancellationToken cancellationToken)
{
var upstreamVersions = await _upstreamClient.ListPackageVersions(id, includeUnlisted : true, cancellationToken);
if (!upstreamVersions.Any())
{
return(null);
}
// Merge the local package versions into the upstream package versions.
var localPackages = await _localPackages.FindAsync(id, includeUnlisted : true);
var localVersions = localPackages.Select(p => p.Version);
return(upstreamVersions.Concat(localVersions).Distinct().ToList());
}
