Show fully booked WooCommerce Bookings time slots on the product page as disabled “FULL” slots for fixed duration product

custom_bookings_show_full_time_slots_fixed_duration.php

/**
   * Show fully booked WooCommerce Bookings time slots
   *
   * By default, WooCommerce Bookings hides time slots once they are fully booked.
   * This snippet keeps those slots visible on the product booking calendar and labels
   * them as "FULL", while leaving them disabled so customers cannot select or
   * book them.
   *
   * Notes:
   * - Applies to fixed duration booking slots on the classic booking form.
   * - Does not apply to customer-defined duration bookings with start/end dropdowns.
   * - The FULL slots intentionally do not include a data-value attribute, so the
   *   Bookings JavaScript cannot select them for checkout.
   */

add_filter( 'wc_bookings_get_time_slots_html', 'custom_bookings_show_full_time_slots', 10, 4 );

  function custom_bookings_show_full_time_slots( $html, $available_blocks, $blocks, $product ) {
        if (
                ! is_a( $product, 'WC_Product_Booking' ) ||
                'customer' === $product->get_duration_type() ||
                ! in_array( $product->get_duration_unit(), array( 'hour', 'minute' ), true )
        ) {
                return $html;
        }

        if ( empty( $blocks ) || ! is_array( $blocks ) ) {
                return $html;
        }

        ksort( $blocks );

        $html = '';

        foreach ( $blocks as $block => $booked_slots ) {
                if ( ! is_numeric( $block ) ) {
                        continue;
                }

                $block     = absint( $block );
                $quantity  = isset( $available_blocks[ $block ] ) && is_array( $available_blocks[ $block ] ) ? $available_blocks[ $block ] :
                array();
                $available = isset( $quantity['available'] ) ? max( 0, absint( $quantity['available'] ) ) : 0;
                $booked    = isset( $quantity['booked'] ) ? absint( $quantity['booked'] ) : absint( $booked_slots );

                $time_label = esc_html( date_i18n( wc_bookings_time_format(), $block ) );
                $block_attr = esc_attr( date( 'Hi', $block ) );

                if ( $available > 0 ) {
                        $value = esc_attr( get_time_as_iso8601( $block ) );

                        if ( $booked > 0 ) {
                                $remaining = sprintf(
                                        _n( '%d left', '%d left', $available, 'woocommerce-bookings' ),
                                        $available
                                );

                                $html .= sprintf(
                                        '<li class="block" data-block="%1$s" data-remaining="%2$d"><a href="#" data-value="%3$s" data-remaining="%4$s">%5$s <small
                                        class="booking-spaces-left">(%6$s)</small></a></li>',
                                        $block_attr,
                                        $available,
                                        $value,
                                        esc_attr( $remaining ),
                                        $time_label,
                                        esc_html( $remaining )
                                );
                        } else {
                                $html .= sprintf(
                                        '<li class="block" data-block="%1$s"><a href="#" data-value="%2$s">%3$s</a></li>',
                                        $block_attr,
                                        $value,
                                        $time_label
                                );
                        }

                        continue;
                }

                $html .= sprintf(
                        '<li class="block fully_booked" data-block="%1$s"><a href="#" class="wc-bookings-slot-full" aria-disabled="true"
                        tabindex="-1">%2$s <small class="booking-spaces-left">(%3$s)</small></a></li>',
                        $block_attr,
                        $time_label,
                        esc_html__( 'FULL', 'woocommerce-bookings' )
                );
        }

        return $html;
  }

  add_action( 'wp_enqueue_scripts', 'custom_bookings_full_time_slot_styles', 20 );

  function custom_bookings_full_time_slot_styles() {
        wp_add_inline_style(
                'wc-bookings-styles',
                '.wc-bookings-booking-form .block-picker li.fully_booked a.wc-bookings-slot-full {
                        opacity: .7;
                        text-decoration: none !important;
                        cursor: not-allowed;
                        pointer-events: none;
                }
                .wc-bookings-booking-form .block-picker li.fully_booked a.wc-bookings-slot-full .booking-spaces-left {
                        font-weight: 700;
                }'
        );
  }