Unable to use enum with array data type - REST API

[picocodes]

I would like to be able to specify enums when creating a REST schema property that accepts an array of values.

For example:

<?PHP
   $query_schema['orderby'] = array(
        'description'       => __( 'Sort collection by object attribute.' ),
         'type'             => array( 'string', 'array' ),
         'default'          => 'id',
         'items'            => array(
              'type' => 'string',
         ),
         'enum'              => array( 'id', 'title', 'date', 'include' ),
         'validate_callback' => 'rest_validate_request_arg',
   );           

[anna.bansaghi]

Hi @picocodes, thank you for your report!

I have tested your schema with this validator ​https://jsonschemalint.com/#!/version/draft-04/markup/json, and not accepting array values is the correct behavior.

What do you think, can you use the schema below instead? It will accept both string values like 'id', and array values like ['id', 'title']:

<?php
   $query_schema['orderby'] = array(
    'description'       => __( 'Sort collection by object attribute.' ),
    'default'           => 'id',
    'oneOf'             => array(
        array(
            'type' => 'string',
            'enum' => array(
                'id',
                'title',
                'date',
                'include'
            )
        ),
        array(
            'type'  => 'array',
            'items' => array(
                'type' => 'string',
                'enum' => array(
                    'id',
                    'title',
                    'date',
                    'include'
                )
            )
        )
    ),
    'validate_callback' => 'rest_validate_request_arg',
);

[anna.bansaghi]

I have just noticed another ticket which was reporting issues with the schema I have suggested: #54740
I am sorry giving bad advice!

Also in that ticket there is a comment with the same enhancement you gave: https://core.trac.wordpress.org/ticket/54740#comment:3