Make post_content and other custom fields required

Question

What's the best way to set the required atribute on html forms in wordpress, for instance I would like post-content to be required, so this code need to be changed:

<textarea class="wp-editor-area" style="height: 300px; margin-top: 37px;" autocomplete="off" cols="40" name="content" id="content"></textarea>

To appear like this:

<textarea required class="wp-editor-area" style="height: 300px; margin-top: 37px;" autocomplete="off" cols="40" name="content" id="content"></textarea>

How can do it by a filter or action hook? This same solution I will also use it for other fields in the publish post form.

What I want is to add the HTML5 required attribute on certain fields, once the page has been rendered.

https://www.w3schools.com/tags/att_input_required.asp https://www.w3schools.com/tags/att_textarea_required.asp

Answer 1

Finally I have solved it as follows:

add_action( 'admin_enqueue_scripts', array($this, 'my_admin_scripts') );

function my_admin_scripts($page) {
    global $post;

    if ($page == "post-new.php" OR $page == "post.php") {
        wp_register_script( 'my-custom-admin-scripts', plugins_url('/js/my-admin-post.js',dirname(__FILE__)), array('jquery', 'jquery-ui-sortable' ) , null, true );
        wp_enqueue_script( 'my-custom-admin-scripts' );             
    }           
}

And put the required atribute by JQuery in the next js code (/js/my-admin-post.js):

// JavaScript Document
jQuery(document).ready(function($) {
    $('#title').attr('required', true);
    $('#content').attr('required', true);
    $('#_my_custom_field').attr('required', true); 
});

Answer 2

Don't rely entirely on JavaScript validations. Use below hook for Server side validation.

function check_if_post_content_set( $maybe_empty, $postarr ) {
// Check if post is already created. IMPORTANT
if($postarr['ID'] && (int)$postarr['ID'] > 0){
    if( !$postarr['post_content'] OR $postarr['post_content'] == '' OR $postarr['post_content'] == NULL ){
        $maybe_empty = true;
    }
}
return $maybe_empty;
}
add_filter( 'wp_insert_post_empty_content', 'check_if_post_content_set', 999999, 2 );