Dynamic language loading in Sanity schemas not currently supported

const supportedLanguages = [
  {
    name: 'fr',
    title: 'Français',
    isDefault: true, // important
  },
  {
    name: 'ja',
    title: '日本語',
  },
  {
    name: 'en',
    title: 'English',
  },
]

export default {
  name: 'localeString',
  title: 'LocaleString',
  type: 'object',
  fieldsets: [
    {
      title: 'Translations',
      name: 'translations',
    },
  ],
  fields: supportedLanguages.map(langx => (
    {
      name: langx.name,
      title: langx.title,
      type: 'text',
      fieldset: langx.isDefault ? null : 'translations',
    }
  )),
}

export default {
    name: 'lang',
    title: 'Langue',
    type: 'document',
    fields: [
        {
            name: 'name',
            title: 'Name',
            type: 'string',
        },
        {
            name: 'title',
            title: 'Title',
            type: 'string',
        },
        {
            name: 'isDefault',
            title: 'IsDefault',
            type: 'boolean',
        },
    ],
}

*[_type == 'lang' ]{name, title, isDefault}

"result":[3 items
0:{3 items
"isDefault":false
"name":"ja"
"title":"日本語"
}
1:{3 items
"isDefault":true
"name":"fr"
"title":"Français"
}
2:{3 items
"isDefault":false
"name":"en"
"title":"English"

const query = '*[_type == "bike" && seats >= $minSeats] {name, seats}'
const params = {minSeats: 2}

client.fetch(query, params).then(bikes => {
  console.log('Bikes with more than one seat:')
  bikes.forEach(bike => {
    console.log(`${bike.name} (${bike.seats} seats)`)
  })
})

import client from 'part:@sanity/base/client'
import groq from "groq"

const query = groq `*[_type == 'lang']{
  name,
  title,
  isDefault
}`
const params = {}

export default {
  name: 'localeString',
  title: 'LocaleString',
  type: 'object',
  fieldsets: [
    {
      title: 'Translations',
      name: 'translations',
    },
  ],
  fields: [
    {
      client.fetch(query, params).then(langs => {
      langs.forEach(lang => ({
        name: lang.name,
        title: lang.title,
        type: 'text',
        fieldset: lang.isDefault ? null : 'translations',
      }))
      })
    }
  ]
}

export default {
  name: 'localeString',
  title: 'LocaleString',
  type: 'object',
  fieldsets: [
    {
      title: 'Translations',
      name: 'translations',
    },
  ],
  fields: [
    {
      client.fetch(query, params).then(langs => {
      langs.forEach(lang => ({
        name: lang.name,
        title: lang.title,
        type: 'string',
        fieldset: lang.isDefault ? null : 'translations',
      }))
      })
    }
  ]
}

import client from 'part:@sanity/base/client'
import groq from "groq"

const query = groq `*[_type == 'lang']{
  name,
  title,
  isDefault
}`
const params = {}

export default {
  name: 'localeString',
  title: 'LocaleString',
  type: 'object',
  fieldsets: [
    {
      title: 'Translations',
      name: 'translations',
    },
  ],
  fields: [
    {
      console.log(lang),
      client.fetch(query, params).then(langs => {
      langs.forEach(lang => ({
        name: lang.name,
        title: lang.title,
        type: 'string',
        fieldset: lang.isDefault ? null : 'translations',
      }))
      })
    }
  ]
}

ERROR in ./schemas/localeString.js
Module build failed: SyntaxError: C:\xampp\htdocs\<http://francois-vidit-2.com|francois-vidit-2.com>\studio\schemas\localeString.js: Unexpected token, expected "," (46:13)

  44 |   fields: [
  45 |     {
> 46 |       console.log(lang),
     |              ^
  47 |       client.fetch(query, params).then(langs => {
  48 |       langs.forEach(lang => ({
  49 |         name: lang.name,

import client from 'part:@sanity/base/client'
import groq from "groq"
const query = groq `*[_type == 'lang']{
  name,
  title,
  isDefault
}`
const params = {}
export default {
  name: 'localeString',
  title: 'LocaleString',
  type: 'object',
  fieldsets: [
    {
      title: 'Translations',
      name: 'translations',
    },
  ],
  fields: 
    client.fetch(query, params).then(langs => {
    langs.map(lang => ({
      name: lang.name,
      title: lang.title,
      type: 'string',
      fieldset: lang.isDefault ? null : 'translations',
    }))
  })
}

The "fields" property must be an array of fields. Instead saw "object

function localize(value, languages) {
  if (Array.isArray(value)) {
    return value.map(v => localize(v, languages))
  } else if (typeof value == 'object') {
    if (/^locale[A-Z]/.test(value._type)) {
      const language = languages.find(lang => value[lang])
      return value[language]
    }
    
    return Object.keys(value).reduce((result, key) => {
      result[key] = localize(value[key], languages)
      return result
    }, {})
  }
  return value
}