lets try it

export const updateUser = mutation({
  args: {
    data: v.optional(userSchema),
  },
  handler: async (ctx, args) => {
    const userId = await getAuthUserId(ctx)
    if (userId === null) {
      throw new ConvexError('Unauthorized')
    }

    if (!args.data) {
      return
    }

    await ctx.db.patch(userId, {
      ...args.data,
    })
  },
})

/**
 * partial helps you define an object of optional validators more concisely.
 *
 * e.g. `partial({a: v.string(), b: v.number()})` is equivalent to
 * `{a: v.optional(v.string()), b: v.optional(v.number())}`
 *
 * @param obj The object of validators to make optional. e.g. {a: v.string()}
 * @returns A new object of validators that can be the value or undefined.
 */
export const partial = (obj) => {
    return Object.fromEntries(Object.entries(obj).map(([k, vv]) => [
        k,
        vv.isOptional === "optional" ? vv : v.optional(vv),
    ]));
};

Type '{ name: VString<string | undefined, "optional">; email: VString<string | undefined, "optional">; username: VString<string | undefined, "optional">; ... 7 more ...; lang: VUnion<...>; }' is not assignable to type 'Validator<any, OptionalProperty, any>'.ts(2322)