I’m trying to insert an item into an array in a custom input component but nothing happens.

import PatchEvent from 'part:@sanity/form-builder/patch-event'

const handleAction = (field) => {
    const patches = [
      { path: [], type: "setIfMissing", value: [] }, 
      {
        type: "insert",
        items: [{ _type: field.name }],
        path: [-1]
      }
    ]

    PatchEvent.from(patches)
}

<Button
  kind="simple"
  items={type.of}
  onAction={(field) => handleAction(field)}
  inverted={true}
>
  Add
</Button>

onChange(PatchEvent.from(insert({items: [{ _type: field.name, path: [-1] }]})).prepend(setIfMissing([])))

Cannot read property 'length' of undefined

const handleAction = (field) => {
    const patches = insert(
      [{ _type: field.name }],
      'after'
    )
    const patchFrom = PatchEvent.from(patches).prepend(setIfMissing([]))
  
    onChange(patchFrom)
}

Attempt to apply insert patch to non-array value

const handleAction = (field) => {
    const patches = insert(
      [{ _type: field.name }],
      'after',
      [-1]
    )
    const patchFrom = PatchEvent.from(patches).prepend(setIfMissing([]))
  
    onChange(patchFrom)
  }