wp-includes/customize/class-wp-customize-sidebar-section.php:55Whether the current sidebar is rendered on the page.
bool public function active_callback() { return $this->manager->widgets->is_sidebar_rendered( $this->sidebar_id ); }Introduced in 4.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/customize/class-wp-customize-sidebar-section.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.