*
 * The snapshot must have children.
 * It is created when we store missing files underneath it, so that we don’t have to query them again and again.
 */
public class UnknownFileSystemNode extends AbstractIncompleteFileSystemNode {

    public UnknownFileSystemNode(ChildMap<? extends FileSystemNode> children) {
        super(children);
        assert !children.isEmpty();
    }

    @Override

class UnknownFileSystemNodeTest extends AbstractIncompleteFileSystemNodeTest<UnknownFileSystemNode> {

    @Override
    protected UnknownFileSystemNode createInitialRootNode(ChildMap<FileSystemNode> children) {
        return new UnknownFileSystemNode(children)
    }

    @Override
    protected boolean isSameNodeType(FileSystemNode node) {
        return node instanceof UnknownFileSystemNode
    }

    @Override

import org.gradle.internal.snapshot.PartialDirectoryNode;
import org.gradle.internal.snapshot.SingletonChildMap;
import org.gradle.internal.snapshot.SnapshotHierarchy;
import org.gradle.internal.snapshot.UnknownFileSystemNode;
import org.gradle.internal.snapshot.VfsRelativePath;

import java.util.Optional;
import java.util.stream.Stream;

public class DefaultSnapshotHierarchy implements SnapshotHierarchy {

                boolean isDirectory = anyChildMatches(children, node -> node.getSnapshot().map(this::isRegularFileOrDirectory).orElse(false));
                return isDirectory ? new PartialDirectoryNode(children) : new UnknownFileSystemNode(children);
            }

            private boolean isRegularFileOrDirectory(MetadataSnapshot metadataSnapshot) {
                return metadataSnapshot.getType() != FileType.Missing;
            }