src/language-html/printer-html.js/getNodeContent
function getNodeContent(node, options) {
  return options.originalText.slice(
    node.startSourceSpan.end.offset +
      (node.firstChild &&
      needsToBorrowParentOpeningTagEndMarker(node.firstChild)
        ? -printOpeningTagEndMarker(node).length
        : 0),
    node.endSourceSpan.start.offset +
      (node.lastChild &&
      needsToBorrowParentClosingTagStartMarker(node.lastChild)
        ? printClosingTagStartMarker(node, options).length
        : needsToBorrowLastChildClosingTagEndMarker(node)
        ? -printClosingTagEndMarker(node.lastChild, options).length
        : 0)
  );
}