gatsby remark transformer plugin that cleans up extraneous wrapper paragraph tags and table whitespace nodes that can raise errors/warnings.

plugins--gatsby-remark-cleaner--index.js

const visit = require(`unist-util-visit`);
const remove = require(`unist-util-remove`);
const HTMLParser = require('node-html-parser');

const matches = (classes, value) => {
  const fragment = HTMLParser.parse(value);
  if (!fragment.firstChild.classList) {
    return false;
  }

  for (const elem of classes) {
    if (fragment.firstChild.classList.contains(elem)) {
      return true;
    }
  }

  return false;
};

module.exports = (refs, {classes, stripTableWhitespaceNodes = true}) => {
  const {markdownAST} = refs;
  visit(markdownAST, 'paragraph', (node, index, parent) => {
    const isCandidate = node.children.every(child => {
      if (!child.value) {
        return;
      }

      if (stripTableWhitespaceNodes) {
        child.value = child.value.replace(/(table|tbody|tfoot|tr)([^>]*?)>\s+</g, '$1$2><').replace(/>\s+<\/(table|tbody|tfoot|tr)/g, '></$1').replace(/\/td>\s+<td/g, '/td><td');
      }

      return (
        (child.type === 'html' && matches(classes, child.value))
        || (child.type === 'text' && child.value === '\n')
      );
    });

    if (!isCandidate) {
      return;
    }

    remove(node, 'text');

    parent.children.splice(index, 1, ...node.children);

    return index;
  });
};

~gatsby-config.js

// File: gatsby-config.js

module.exports = {
  // Other config
  plugins: [
    // Other plugins
    {
      resolve: 'gatsby-plugin-mdx',
      options: {
        // Other mdx options
        gatsbyRemarkPlugins: [
          // Other remark plugins
          {
            resolve: require.resolve('./plugins/gatsby-remark-cleaner'),
            options: {
              classes: [
                // list of classes to remove wrapping p tag from, eg.
                // 'gatsby-resp-iframe-wrapper' is used by 'gatsby-remark-responsive-iframe' (also 'gatsby-remark-embed-video')
                // 'gist' is used by 'gatsby-remark-embed-gist'
              ],
              // Removes table whitespace nodes that can raise errors, observed in 'gatsby-remark-embed-gist'. Defaults to true.
              stripTableWhitespaceNodes: true,
            },
          },
        ],
      },
    },
  ],
};