private static PsiElement @Nullable [] computeInclusion(final XmlTag xincludeTag) {
    final XmlFile included = XmlIncludeHandler.resolveXIncludeFile(xincludeTag);
    if (IdempotenceChecker.isLoggingEnabled()) {
      IdempotenceChecker.logTrace("InclusionProvider resolved file=" + included);
    }
    final XmlDocument document = included != null ? included.getDocument() : null;
    final XmlTag rootTag = document != null ? document.getRootTag() : null;
    if (rootTag != null) {
      final String xpointer = xincludeTag.getAttributeValue("xpointer", XmlPsiUtil.XINCLUDE_URI);
      final XmlTag[] includeTag = extractXpointer(rootTag, xpointer);
      if (IdempotenceChecker.isLoggingEnabled()) {
        IdempotenceChecker.logTrace("InclusionProvider found " + includeTag.length + " tags by " + xpointer);
      }
      PsiElement[] result = new PsiElement[includeTag.length];
      for (int i = 0; i < includeTag.length; i++) {
        result[i] = new IncludedXmlTag(includeTag[i], xincludeTag.getParentTag());
      }
      return result;
    }

    return null;
  }
private static PsiElement @Nullable [] computeInclusion(final XmlTag xincludeTag)