Why withValidation() doesn't convert to the correct types?

[nemanjam]

I have Zod schema that has booleans and numbers, not just strings.

export const postsGetSchema = z.object({
  page: z.preprocess(stringToNumber, z.number().min(1).optional()), // number
  limit: z.preprocess(stringToNumber, z.number().min(1).max(postsLimitMax).optional()), // number
  searchTerm: z.string().optional().or(z.literal('')),
  userId: z.string().cuid().optional().or(z.literal('')),
  email: z.string().email().optional().or(z.literal('')),
  username: z.string().optional().or(z.literal('')),
  sortDirection: z
    .string()
    .optional()
    .or(z.literal(''))
    .or(z.literal('asc'))
    .or(z.literal('desc')),
  published: z.preprocess(stringToBoolean, z.boolean().optional()), // boolean
});

const stringToNumber = (numberStr: string): number | void => {
  return numberStr ? parseInt(z.string().parse(numberStr), 10) : undefined;
};

const stringToBoolean = (booleanStr: string): boolean | void => {
  return booleanStr ? z.string().parse(booleanStr) === 'true' : undefined;
};

And I use it to validate query string:

const validatePostsGet = withValidation({
  schema: postsGetSchema,
  type: 'Zod',
  mode: 'query',
});

handler.get(
  validatePostsGet(),
  async (
    req: NextApiRequest,
    res: NextApiResponse<PaginatedResponse<PostWithAuthor>>
  ) => {
    console.log('req.query', req.query);
    const posts = await getPosts(req.query); // convert types...
    res.status(200).json(posts);
  }
);

// example output
// req.query { page: '1', userId: 'cl1ur7dyd03615ipn9bll3x5a', published: 'false' }

but validatePostsGet() middleware just does validation, all values in req.query remain strings after validation. So I need one additional step and helper function to convert strings to correct types which feels inconvenient and could be done in validation middleware and attached to req.query. like parse() from Zod does.

Is it possible to add option to withValidation() to convert values to correct types?

[jellydn]

Hi @nemanjam

Is it possible to add option to withValidation() to convert values to correct types?`

Yeah, could you send PR about this feature? I think this is a common usage for everyone when using zod. Thanks.

[nemanjam]

I would love to, but I am not yet that experienced with validation libraries.