Initialise customer sessions on the order pay page

plugins/woocommerce/changelog/43858-fix-23902-create-session-on-page-page

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Fix to ensure all customers have a session when visiting the order pay page.

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

@@ -71,6 +71,7 @@ public function init() {
 		$this->init_session_cookie();
 
 		add_action( 'woocommerce_set_cart_cookies', array( $this, 'set_customer_session_cookie' ), 10 );
+		add_action( 'wp', array( $this, 'maybe_set_customer_session_cookie' ), 99 );
 		add_action( 'shutdown', array( $this, 'save_data' ), 20 );
 		add_action( 'wp_logout', array( $this, 'destroy_session' ) );
 
@@ -137,14 +138,26 @@ private function is_session_cookie_valid() {
 			return false;
 		}
 
-		// Session from a different user is not valid. (Although from a guest user will be valid)
+		// Session from a different user is not valid. (Although from a guest user will be valid).
 		if ( is_user_logged_in() && ! $this->is_customer_guest( $this->_customer_id ) && strval( get_current_user_id() ) !== $this->_customer_id ) {
 			return false;
 		}
 
 		return true;
 	}
 
+	/**
+	 * Hooks into the wp action to maybe set the session cookie if the user is on a certain page e.g. a checkout endpoint.
+	 *
+	 * Certain gateways may rely on sessions and this ensures a session is present even if the customer does not have a
+	 * cart.
+	 */
+	public function maybe_set_customer_session_cookie() {
+		if ( is_wc_endpoint_url( 'order-pay' ) ) {
+			$this->set_customer_session_cookie( true );
+		}
+	}
+
 	/**
 	 * Sets the session cookie on-demand (usually after adding an item to the cart).
 	 *