Markdown Paste Handling for Sanity Studio v2 using micromark

handlePaste.js

/* Remember: 
sanity install @sanity/code-input
yarn add micromark 
*/
import { micromark } from 'micromark'
import { htmlToBlocks } from '@sanity/block-tools'

export async function handlePaste(input) {
  const { event, type, path } = input
  const text = event.clipboardData.getData('text/plain')

  if (text) {
    const html = micromark(text)
    if (html) {
      const blocks = htmlToBlocks(html, type, {
        rules: [
          {
            deserialize(el, next, block) {
              if (!el || !el.children || (el.tagName && el.tagName.toLowerCase() !== 'pre')) {
                return undefined
              }
              const codeElement = el.children[0]
              const childNodes =
                codeElement && codeElement.tagName.toLowerCase() === 'code' ? codeElement.childNodes : el.childNodes
              let code = ''
              childNodes.forEach((node) => {
                code += '\n' + node.textContent + '\n'
              })
              const language = codeElement && codeElement.className ? codeElement.className.replace('language-', '') : ''
              return block({
                _type: 'code',
                language,
                code,
              })
            },

          },
        ]
      })
      // return an insert patch
      return { insert: blocks, path }
    }
  }
}

post.js

import React, { forwardRef } from 'react'
import { BlockEditor } from 'part:@sanity/form-builder'
import { handlePaste } from './handlePaste'

const CustomEditor = forwardRef((props, ref) => (<BlockEditor
  {...props}
  ref={ref}
  onPaste={handlePaste}
/>
))

export default {
  name: 'post',
  type: 'document',
  title: 'Post',
  fields: [
    {
      name: 'title',
      type: 'string',
      title: 'Title',
    },
    {
      name: 'body',
      type: 'array',
      title: 'Body',
      of: [{ type: 'block' }, { type: 'code' }],
      inputComponent: CustomEditor,
    }
  ]
}