The source node in most cases contains the sample message as written by the developer. If it looks like a dot-delimitted string such as "form.label.firstname", then the developer has not provided a default message.

This voucher has already been added to the basket This voucher has already been added to the basket key: msg.voucher_already_used The validation of this voucher was not successful. The validation of this voucher was not successful. key: msg.voucher_invalid The voucher was removed from your basket. The voucher was removed from your basket. key: msg.voucher_removed_success The voucher was added successfully. The voucher was added successfully. key: msg.voucher_success The vouchers were removed from your basket. The vouchers were removed from your basket. key: msg.vouchers_removed_success