[Enhancement]: New Action to fire before WC_Session_Handler converts a guest session to login.

[georgestephanis]

Describe the solution you'd like

I'd like to request an action be slipped in to fire either in in WC_Session_Handler::save_data()

woocommerce/plugins/woocommerce/includes/class-wc-session-handler.php

Lines 349 to 375 in 487c7a8

	/**
	* Save data and delete guest session.
	*
	* @param int $old_session_key session ID before user logs in.
	*/
	public function save_data( $old_session_key = 0 ) {
	// Dirty if something changed - prevents saving nothing new.
	if ( $this->_dirty && $this->has_session() ) {
	global $wpdb;
	$wpdb->query(
	$wpdb->prepare(
	"INSERT INTO {$wpdb->prefix}woocommerce_sessions (`session_key`, `session_value`, `session_expiry`) VALUES (%s, %s, %d)
	ON DUPLICATE KEY UPDATE `session_value` = VALUES(`session_value`), `session_expiry` = VALUES(`session_expiry`)",
	$this->_customer_id,
	maybe_serialize( $this->_data ),
	$this->_session_expiration
	)
	);
	wp_cache_set( $this->get_cache_prefix() . $this->_customer_id, $this->_data, WC_SESSION_CACHE_GROUP, $this->_session_expiration - time() );
	$this->_dirty = false;
	if ( get_current_user_id() != $old_session_key && ! is_object( get_user_by( 'id', $old_session_key ) ) ) {
	$this->delete_session( $old_session_key );
	}
	}
	}

or WC_Session_Handler::init_session_cookie()

woocommerce/plugins/woocommerce/includes/class-wc-session-handler.php

Lines 83 to 123 in 487c7a8

	/**
	* Setup cookie and customer ID.
	*
	* @since 3.6.0
	*/
	public function init_session_cookie() {
	$cookie = $this->get_session_cookie();
	if ( $cookie ) {
	// Customer ID will be an MD5 hash id this is a guest session.
	$this->_customer_id = $cookie[0];
	$this->_session_expiration = $cookie[1];
	$this->_session_expiring = $cookie[2];
	$this->_has_cookie = true;
	$this->_data = $this->get_session_data();
	if ( ! $this->is_session_cookie_valid() ) {
	$this->destroy_session();
	$this->set_session_expiration();
	}
	// If the user logs in, update session.
	if ( is_user_logged_in() && strval( get_current_user_id() ) !== $this->_customer_id ) {
	$guest_session_id = $this->_customer_id;
	$this->_customer_id = strval( get_current_user_id() );
	$this->_dirty = true;
	$this->save_data( $guest_session_id );
	$this->set_customer_session_cookie( true );
	}
	// Update session if its close to expiring.
	if ( time() > $this->_session_expiring ) {
	$this->set_session_expiration();
	$this->update_session_timestamp( $this->_customer_id, $this->_session_expiration );
	}
	} else {
	$this->set_session_expiration();
	$this->_customer_id = $this->generate_customer_id();
	$this->_data = $this->get_session_data();
	}
	}

that will let plugins listen for when a guest_session_id is getting blown away and its data transferred to a user_id.

Something like do_action( 'wc_migrate_guest_session_key', $old_session_key, $user_id ); or the like.

This would let third-party code either connect the prior session key to a user id for data storage, or migrate the old session id to a different cookie that would enable discrete sessions even if multiple browsers authenticated to the same user_id.

Describe alternatives you've considered

If this isn't considered, I've evaluated doing a much messier workaround, that being duplicating the session key in a side channel, and watching for it to change or for there be a logged in user concurrent with it, and try to ensure I'm catching the event before WooCommerce clears it, but it feels very ... klunky, liable to race conditions, and adding overhead to every page load.

Additional context

For plugins that are providing additional context on user flows, the ability to be connect the pre-login result of WC()->session->get_customer_unique_id() to the post-login result where it returns a user_id instead can ensure a more seamless experience for customers without overcomplicated workarounds.

[coreymckrill]

👍 We try to be careful about adding new action and filter hooks, but this seems like a worthy addition to me. If you spin up a PR for this, @georgestephanis, we'll take a look.

[georgestephanis]

PR put together!