Customizer: aggregated multidimensional settings overwrite changes made outside the Customizer

[mattwiebe]

4.4's aggregated multidimensional settings naïvely assumes that no other code will touch the root setting, but that's not necessarily true. Here's some pseudo code from WP.com:

<?php
$wp_customize->add_setting( 'custom_colors[colors]', array(
  'sanitize_callback' => 'wpcom_sanitize_colors'
) );
function wpcom_sanitize_colors( $colors ) {
  // do some sanitization
  // update the CSS used to output colors
  $opts = get_option( 'custom_colors', array() );
  $opts['css'] = wpcom_create_css_for_colors( $colors );
  update_option( 'custom_colors', $opts );
  return $colors;
}

Unfortunately, the new aggregated multidimensional setting code assumes that the Customizer is the only thing that might make a setting change in WP and blindly overwrites the base option/theme_mod. In the above code, the css member will either reflect outdated colors, or not be set at all.

What should probably happen is that the root value should be freshly grabbed in set_root_value() and array_merge'd with the current aggregate. Or maybe that code should be in update()? In any case, this broke a few things on WP.com when we finally started pushing out 4.4 code.

[westonruter]

@mattwiebe: So are you saying that a sanitize callback is actually doing a write operation on the value for another setting, or rather here the setting root? If so, then I would say this would be a bad practice since as far as I see it, the sanitize should be a read-only operation. I'd suggest a better approach to be to hook into the customize_save_after action, like this:

<?php
$wp_customize->add_setting( 'custom_colors[colors]', array(
        'type' => 'option',
        'default' => array(),
        'sanitize_callback' => function( $colors ) { /* ... */ return $colors; },
) );

add_action( 'customize_save_after', function ( $wp_customize ) {
        $is_colors_changed = array_key_exists( 
                'custom_colors[colors]', 
                $wp_customize->unsanitized_post_values() 
        );
        if ( $is_colors_changed ) {
                // update the CSS used to output colors
                $opts = get_option( 'custom_colors', array() );
                $opts['css'] = wpcom_create_css_for_colors( $colors );
                update_option( 'custom_colors', $opts );
        }
} );

[westonruter]

Closing due to inactivity and an alternative solution which I believe to be better and renders the issue invalid.