@wordpress/blocks/build-module/api/raw-handling/special-comment-converter.js

Block API for WordPress.

/**
 * WordPress dependencies
 */
import { remove, replace } from '@wordpress/dom';

/**
 * Looks for `<!--nextpage-->` and `<!--more-->` comments and
 * replaces them with a custom element representing a future block.
 *
 * The custom element is a way to bypass the rest of the `raw-handling`
 * transforms, which would eliminate other kinds of node with which to carry
 * `<!--more-->`'s data: nodes with `data` attributes, empty paragraphs, etc.
 *
 * The custom element is then expected to be recognized by any registered
 * block's `raw` transform.
 *
 * @param {Node}     node The node to be processed.
 * @param {Document} doc  The document of the node.
 * @return {void}
 */
export default function specialCommentConverter(node, doc) {
  if (node.nodeType !== node.COMMENT_NODE) {
    return;
  }
  if (node.nodeValue !== 'nextpage' && node.nodeValue.indexOf('more') !== 0) {
    return;
  }
  const block = createBlock(node, doc);

  // If our `<!--more-->` comment is in the middle of a paragraph, we should
  // split the paragraph in two and insert the more block in between. If it's
  // inside an empty paragraph, we should still move it out of the paragraph
  // and remove the paragraph. If there's no paragraph, fall back to simply
  // replacing the comment.
  if (!node.parentNode || node.parentNode.nodeName !== 'P') {
    replace(node, block);
  } else {
    const childNodes = Array.from(node.parentNode.childNodes);
    const nodeIndex = childNodes.indexOf(node);
    const wrapperNode = node.parentNode.parentNode || doc.body;
    const paragraphBuilder = (acc, child) => {
      if (!acc) {
        acc = doc.createElement('p');
      }
      acc.appendChild(child);
      return acc;
    };

    // Split the original parent node and insert our more block
    [childNodes.slice(0, nodeIndex).reduce(paragraphBuilder, null), block, childNodes.slice(nodeIndex + 1).reduce(paragraphBuilder, null)].forEach(element => element && wrapperNode.insertBefore(element, node.parentNode));

    // Remove the old parent paragraph
    remove(node.parentNode);
  }
}
function createBlock(commentNode, doc) {
  if (commentNode.nodeValue === 'nextpage') {
    return createNextpage(doc);
  }

  // Grab any custom text in the comment.
  const customText = commentNode.nodeValue.slice(4).trim();

  /*
   * When a `<!--more-->` comment is found, we need to look for any
   * `<!--noteaser-->` sibling, but it may not be a direct sibling
   * (whitespace typically lies in between)
   */
  let sibling = commentNode;
  let noTeaser = false;
  while (sibling = sibling.nextSibling) {
    if (sibling.nodeType === sibling.COMMENT_NODE && sibling.nodeValue === 'noteaser') {
      noTeaser = true;
      remove(sibling);
      break;
    }
  }
  return createMore(customText, noTeaser, doc);
}
function createMore(customText, noTeaser, doc) {
  const node = doc.createElement('wp-block');
  node.dataset.block = 'core/more';
  if (customText) {
    node.dataset.customText = customText;
  }
  if (noTeaser) {
    // "Boolean" data attribute.
    node.dataset.noTeaser = '';
  }
  return node;
}
function createNextpage(doc) {
  const node = doc.createElement('wp-block');
  node.dataset.block = 'core/nextpage';
  return node;
}
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