@NotNull
  private static XmlFileHeader calcXmlFileHeader(final XmlFile file) {

    if (file instanceof PsiFileEx
        && ((PsiFileEx) file).isContentsLoaded()
        && file.getNode().isParsed()) {
      return computeHeaderByPsi(file);
    }

    if (!XmlUtil.isStubBuilding() && file.getFileType() == XmlFileType.INSTANCE) {
      VirtualFile virtualFile = file.getVirtualFile();
      if (virtualFile instanceof VirtualFileWithId) {
        ObjectStubTree tree =
            StubTreeLoader.getInstance().readFromVFile(file.getProject(), virtualFile);
        if (tree != null) {
          Stub root = tree.getRoot();
          if (root instanceof FileStub) {
            return ((FileStub) root).getHeader();
          }
        }
      }
    }

    if (!file.isValid()) return XmlFileHeader.EMPTY;

    return NanoXmlUtil.parseHeader(file);
  }
  @NotNull
  private static XmlFileHeader calcXmlFileHeader(final PsiFile file) {

    // if (file.getFileType() == XmlFileType.INSTANCE) {
    //  VirtualFile virtualFile = file.getVirtualFile();
    //  if (virtualFile instanceof VirtualFileWithId) {
    //    ObjectStubTree tree = StubTreeLoader.getInstance().readFromVFile(file.getProject(),
    // virtualFile);
    //    if (tree != null) {
    //      return ((FileStub)tree.getRoot()).getHeader();
    //    }
    //  }
    // }
    if (file instanceof XmlFile && file.getNode().isParsed()) {
      final XmlDocument document = ((XmlFile) file).getDocument();
      if (document != null) {
        String publicId = null;
        String systemId = null;
        final XmlProlog prolog = document.getProlog();
        if (prolog != null) {
          final XmlDoctype doctype = prolog.getDoctype();
          if (doctype != null) {
            publicId = doctype.getPublicId();
            systemId = doctype.getSystemId();
            if (systemId == null) {
              systemId = doctype.getDtdUri();
            }
          }
        }

        final XmlTag tag = document.getRootTag();
        if (tag != null) {
          String localName = tag.getLocalName();
          if (StringUtil.isNotEmpty(localName)) {
            if (tag.getPrevSibling() instanceof PsiErrorElement) {
              return XmlFileHeader.EMPTY;
            }

            String psiNs = tag.getNamespace();
            return new XmlFileHeader(
                localName,
                psiNs == XmlUtil.EMPTY_URI || Comparing.equal(psiNs, systemId) ? null : psiNs,
                publicId,
                systemId);
          }
        }
      }
      return XmlFileHeader.EMPTY;
    }

    if (!file.isValid()) return XmlFileHeader.EMPTY;
    return NanoXmlUtil.parseHeader(file);
  }