public function all(array $args = []): array
    {
        // Establish args.

        $default_args = [
            // Unique.
            'max'         => PHP_INT_MAX,
            'fail_on_max' => false,

            // Also used by {@link total()}.
            'include'                   => [],
            'exclude'                   => [],
            'exclude_deprecated_levels' => true,
            'no_cache'                  => false,
        ];
        $args = array_merge($default_args, $args);
        $args = array_intersect_key($args, $default_args);

        // Unique.
        $args['max']         = max(1, (int) $args['max']);
        $args['fail_on_max'] = (bool) $args['fail_on_max'];

        // Also used by {@link total()}.
        $args['include']                   = (array) $args['include'];
        $args['exclude']                   = (array) $args['exclude'];
        $args['exclude_deprecated_levels'] = (bool) $args['exclude_deprecated_levels'];
        $args['no_cache']                  = (bool) $args['no_cache'];

        // Check cache; already did this query?

        $cache_keys = $args; // Keys to consider when checking the cache.
        unset($cache_keys['no_cache']); // Cache key exclusions.

        if (($caps = &$this->cacheKey(__FUNCTION__, $cache_keys)) !== null && !$args['no_cache']) {
            return $caps; // Already cached this.
        }
        // Automatically fail if there are too many; when/if desirable.

        if ($args['fail_on_max'] && $this->total($args) > $args['max']) {
            return $caps = []; // Fail; too many.
        }
        // Return the array of all caps now.

        $caps = $this->collectAll(); // All possible caps.

        $caps = $args['include'] ? array_intersect_key($caps, array_fill_keys($args['include'], true)) : $caps;
        $caps = $args['exclude'] ? array_diff_key($caps, array_fill_keys($args['exclude'], true)) : $caps;
        $caps = $args['exclude_deprecated_levels'] ? array_diff_key($caps, array_fill_keys($this->deprecated_levels, true)) : $caps;

        asort($caps, SORT_NATURAL); // Sort naturally.

        return $caps;
    }