Adding type to unique slug validation in Sanity.io

// /lib/isUniqueAcrossAllDocuments.js

// Note: this assumes that every document that has a slug field
// have it on the `slug` field at the root
export async function isUniqueAcrossAllDocuments(slug, context) {
  const {document, getClient} = context
  const client = getClient({apiVersion: '2022-12-07'})
  const id = document._id.replace(/^drafts\./, '')
  const params = {
    draft: `drafts.${id}`,
    published: id,
    slug,
  }
  const query = `!defined(*[!(_id in [$draft, $published]) && slug.current == $slug][0]._id)`
  const result = await client.fetch(query, params)
  return result
}

defineField({
      name: 'slug',
      title: 'Slug',
      type: 'slug',
      options: {
        source: 'title',
        maxLength: 96,
        isUnique: async (slug, context) => {
         // Search for all documents with the same slug
          const query = `*[_type == "post" && slug.current == $slug]`;
          
          const documents = await context.getClient({ apiVersion }).fetch<Post[]>(query, {
            slug,
          });
          // Returns true if no documents are found, false otherwise
          return documents.length <= 1;
        },
      },
    }),