private static List<MavenArtifact> getUnresolvedExtensions(State state) {
    synchronized (state) {
      if (state.myUnresolvedExtensionsCache == null) {
        List<MavenArtifact> result = new ArrayList<>();
        for (MavenArtifact each : state.myExtensions) {
          // Collect only extensions that were attempted to be resolved.
          // It is because embedder does not even try to resolve extensions that
          // are not necessary.
          if (state.myUnresolvedArtifactIds.contains(each.getMavenId())
              && !pomFileExists(state.myLocalRepository, each)) {
            result.add(each);
          }
        }
        state.myUnresolvedExtensionsCache = result;
      }
      return state.myUnresolvedExtensionsCache;
    }
  }
private static List<MavenArtifact> getUnresolvedExtensions(State state)