TypeGen not generating union type for string array with list option

[oyvind-stenhaug]

Describe the bug

If I define a string field with a list of predefined values, TypeGen generates a union type for that field. However, if I define an array field with a list of predefined values (to get checkboxes in the studio), TypeGen just generates Array<string> as the type of that field.

To Reproduce

Steps to reproduce the behavior:

1. Create a project (opting in to TypeScript) or edit an existing one, and make a sanity.config.ts that's something like this:

import {defineConfig, defineType, defineField} from 'sanity'

export default defineConfig({
  name: 'default',
  title: '<your_project_title>',
  projectId: '<your_project_id>',
  schema: {
    types: [
      defineType({
        type: 'document',
        title: 'Test',
        name: 'test',
        fields: [
          defineField({
            name: 'category',
            type: 'string',
            options: {
              list: ['physics', 'chemistry'],
            },
          }),
          defineField({
            name: 'element',
            type: 'array',
            of: [{type: 'string'}],
            options: {
              list: ['physics', 'chemistry'],
            },
          }),
        ],
      }),
    ],
  },
})

2. npx sanity schema extract && npx sanity typegen generate and observe the generated types (e.g. sanity.types.ts)

Expected behavior

export type Test = {
  _id: string
  _type: 'test'
  _createdAt: string
  _updatedAt: string
  _rev: string
  category?: 'physics' | 'chemistry'
  element?: Array<'physics' | 'chemistry'>
}

Actual behavior

export type Test = {
  _id: string
  _type: 'test'
  _createdAt: string
  _updatedAt: string
  _rev: string
  category?: 'physics' | 'chemistry'
  element?: Array<string>
}

Which versions of Sanity are you using?

@sanity/cli (global)          3.41.1 (up to date)
@sanity/eslint-config-studio   4.0.0 (up to date)
@sanity/vision                3.41.1 (up to date)
sanity                        3.41.1 (up to date)

What operating system are you using?

GNU/Linux (Ubuntu 22.04.4 LTS)

Which versions of Node.js / npm are you running?
npm -v && node -v:

10.2.4
v20.11.1