Package Identity Function

nugetloader.packageid.cs

private async Task<PackageIdentity> GetPackageIdentity(
  ExtensionConfiguration extConfig, SourceCacheContext cache, ILogger nugetLogger, 
  IEnumerable<SourceRepository> repositories, CancellationToken cancelToken)
{
  // Go through each repository.
  // If a repository contains only pre-release packages (e.g. AutoStep CI), and 
  // the configuration doesn't permit pre-release versions,
  // the search will look at other ones (e.g. NuGet).
  foreach (var sourceRepository in repositories)
  {
    // Get a 'resource' from the repository.
    var findPackageResource = await sourceRepository.GetResourceAsync<FindPackageByIdResource>();

    // Get the list of all available versions of the package in the repository.
    var allVersions = await findPackageResource.GetAllVersionsAsync(extConfig.Package, cache, nugetLogger, cancelToken);

    NuGetVersion selected;

    // Have we specified a version range?
    if (extConfig.Version != null)
    {
      if (!VersionRange.TryParse(extConfig.Version, out var range))
      {
        throw new Exception("Invalid version range provided.");
      }

      // Find the best package version match for the range.
      // Consider pre-release versions, but only if the extension is configured to use them.
      var bestVersion = range.FindBestMatch(allVersions.Where(v => extConfig.PreRelease || !v.IsPrerelease));

      selected = bestVersion;
    }
    else
    {
      // No version; choose the latest, allow pre-release if configured.
      selected = allVersions.LastOrDefault(v => v.IsPrerelease == extConfig.PreRelease);
    }

    if (selected is object)
    {
      return new PackageIdentity(extConfig.Package, selected);
    }
  }

  return null;
}