Function uniqueSlug

uniqueSlug(
    options?: { apiVersion?: string; field?: string },
): (
    slug: SlugValue | undefined,
    context: ValidationContext,
) => Promise<string | true>
Create a slug uniqueness validation rule that checks for duplicate slugs within the same document type.

Use this in your schema's slug field validation to give editors immediate feedback before publishing.
Parameters
- Optionaloptions: { apiVersion?: string; field?: string }
  Optional configuration
  - OptionalapiVersion?: string
    Sanity API version (default: '2024-01-01')
  - Optionalfield?: string
Returns (
slug: SlugValue | undefined,
context: ValidationContext,
) => Promise<string | true>
A custom validation function for use with rule.custom()
Example
```
import { defineField } from 'sanity'
import { uniqueSlug } from '@sanity/routes/studio'

defineField({
  name: 'slug',
  type: 'slug',
  validation: (rule) => rule.required().custom(uniqueSlug()),
})
```
Example
```
// With custom slug field name
defineField({
  name: 'permalink',
  type: 'slug',
  validation: (rule) => rule.required().custom(uniqueSlug({ field: 'permalink' })),
})
```
- Defined in packages/routes/src/validation.ts:36