Drag-and-drop fails when array contains both image and object types

[joaodotwork]

Describe the bug

Drag-and-drop image upload fails with error "The following item can't be uploaded because there's no known conversion from content type to array item" when an array field contains both image type members and custom object type members.

To Reproduce

Schema:

// Custom object type (not image or file)
defineType({
  name: 'video',
  type: 'object',
  fields: [
    defineField({ name: 'muxVideo', type: 'mux.video' }),
    defineField({ name: 'caption', type: 'string' })
  ]
})

// Array mixing image and object types
defineType({
  name: 'work',
  type: 'document',
  fields: [
    defineField({
      name: 'images',
      type: 'array',
      of: [
        {type: 'image'},  // or custom image type
        {type: 'video'}   // custom object - breaks upload
      ]
    })
  ]
})

Steps:

1. Create document with mixed-type array as above
2. Drag JPEG file onto the array field
3. Error appears instead of upload

Expected behavior

Upload resolver should:

• Recognize the dragged file is an image
• Match it to the image array member type
• Upload successfully to that member

Actual behavior

Error dialog: "The following item can't be uploaded because there's no known conversion from content type to array item: filename.jpg (image/jpeg)"

Upload via Browse button works fine.

Root cause (investigation)

The upload resolver in getUploadCandidates() iterates all array member types and calls resolveUploader(memberType, file) for each. When it encounters the video object type:

// From node_modules/sanity/lib/index.js
function resolveUploader(type, file) {
  return uploaders.find((uploader) => 
    is$1(uploader.type, type) &&           // Checks if type is 'image' or 'file'
    accepts(file, uploader.accepts) &&
    accepts(file, type.options?.accept || "")
  ) || null;
}

The is$1('image', videoObjectType) fails because the custom object doesn't extend image or file. This causes resolveUploader to return null for the object member. If ANY member returns null, the entire drop is rejected.

Workaround

Remove object types from arrays that need drag-and-drop:

of: [{type: 'image'}]  // Works

Use separate fields for non-image/file content.

Environment

• Sanity Studio: v5.7.0
• React: v19.1
• Browser: Chrome 131

Impact

Cannot use drag-and-drop with mixed content galleries (images + videos, images + embeds, etc.). Must split into separate arrays or use Upload button.

[jordanl17]

Hi @joaodotwork thank you for reporting this bug, and especially appreciate the time you've taken to investigate the source of the issue. We have taken this into our backlog and will update here once we have prioritised working on a fix

[jordanl17]

Hi @joaodotwork I believe this might have been resolved by this fix - #11907

I think it might be a red herring that this looks broken for mixed arrays, and the issue might actually have been because no Uploader had been defined.

This PR fix is in sanity@next currently, and will shortly be coming to@latest if you'd like to test the fix and report back whether this has resolved the issue for you.

Thanks

[github-actions]

Hi there, thanks again for this issue report. We have had a look into it and are currently waiting for some more information. If you are able to help by providing any further details as requested above that would be a great help. If you are no longer experiencing this issue, or aren't able to provide any further details, this issue will be closed in another 4 days.