Function cloneShadow

packages/blockly/core/xml.ts:332–372

* Deeply clone the shadow's DOM so that changes don't back-wash to the block. * * @param shadow A tree of XML elements. * @param opt_noId True if the encoder should skip the block ID. * @returns A tree of XML elements.

(shadow: Element, opt_noId?: boolean)

 * @returns A tree of XML elements.
 */
function cloneShadow(shadow: Element, opt_noId?: boolean): Element {
  shadow = shadow.cloneNode(true) as Element;
  // Walk the tree looking for whitespace.  Don't prune whitespace in a tag.
  let node: Node | null = shadow;
  let textNode;
  while (node) {
    if (opt_noId && node.nodeName === 'shadow') {
      // Strip off IDs from shadow blocks.  There should never be a 'block' as
      // a child of a 'shadow', so no need to check that.
      (node as Element).removeAttribute('id');
    }
    if (node.firstChild) {
      node = node.firstChild;
    } else {
      while (node && !node.nextSibling) {
        textNode = node;
        node = node.parentNode;
        if (
          textNode.nodeType === dom.NodeType.TEXT_NODE &&
          (textNode as Text).data.trim() === '' &&
          node?.firstChild !== textNode
        ) {
          // Prune whitespace after a tag.
          dom.removeNode(textNode);
        }
      }
      if (node) {
        textNode = node;
        node = node.nextSibling;
        if (
          textNode.nodeType === dom.NodeType.TEXT_NODE &&
          (textNode as Text).data.trim() === ''
        ) {
          // Prune whitespace before a tag.
          dom.removeNode(textNode);
        }
      }
    }
  }
  return shadow;
}

/**
 * Converts a DOM structure into plain text.