How to get originalFilename from asset using getFileAsset with asset-utils?

Based on the @sanity/asset-utils library documentation, I need to clarify an important point about the originalFilename option you're passing to getFileAsset:

The originalFilename option doesn't work the way you're expecting. Here's why:

The Issue

The @sanity/asset-utils package does not resolve information from the Sanity API - it only works with the information you pass to it. This is explicitly stated in the library's documentation:

"This package does not resolve any information from the Sanity APIs - it does no asynchronous operations and only has the information that you pass it."

What originalFilename Actually Does

Looking at the getVanityStub function, the originalFilename option is used for building URLs with vanity filenames (the human-readable filename at the end of asset URLs), not for retrieving the original filename from an asset.

The Solution

To get the originalFilename of an asset, you need to query it from the Sanity API directly. The asset document itself contains this field. Here's how:

import {getClient} from '@sanity/client'

const client = getClient({
  projectId: 'xxxxxxx',
  dataset: 'staging',
  apiVersion: '2024-01-01',
  useCdn: false
})

// Query the asset document to get originalFilename
const asset = await client.fetch(
  `*[_id == $assetId][0]{
    _id,
    url,
    originalFilename
  }`,
  {assetId: 'file-xxxxx-xxx'}
)

console.log(asset.originalFilename) // This will have the original filename

The @sanity/asset-utils library is designed for parsing and building asset URLs/paths from known information, not for fetching asset metadata from the API. For metadata like originalFilename, size, mimeType, etc., you'll need to query the Sanity Content Lake directly.