'show vpn ike sa' always returns nothing, regardless of any active SAs.
'show vpn ipsec sa' now returns rather less meaningful output.
The root cause is the upgrade of strongswan with the upgrade from vyos 1.1 to 1.2.
In a similar vein, there are various other vpn show commands and helper functions that aren't clearly exposed by the interface.
I've re-worked various bits, and will submit a pull request with more information.