ZONE_CHANGE_GROUP event must be reworked to fix duplicated events

[JayDi85]

From #7572 (comment)

Group event (ZONE_CHANGE_GROUP) introduced long ago for triggers like whenever one or more cards (example: [[The Gitrog Monster]]). E.g. you must catch only one event at the end and trigger on it. ~13 cards uses it.

Current grouping code splits events by zones/source/player (see ZoneChangeData), e.g. it creates multiple group events instead one. It can be potentially buggy for some some use cases.

Possible solution: do not split events by multiple groups. Use one group instead. And keep all necessary information (cards/tokens list, map between card and original event).

[github-actions]

The Gitrog Monster - (Gatherer) (Scryfall) (EDHREC)

{3}{B}{G}
Legendary Creature — Frog Horror
6/6
Deathtouch
At the beginning of your upkeep, sacrifice The Gitrog Monster unless you sacrifice a land.
You may play an additional land on each of your turns.
Whenever one or more land cards are put into your graveyard from anywhere, draw a card.

[theelk801]

this is another thing I was hoping to work on soon once there aren't any new sets coming out for a little while

[jeffwadsworth]

It doesn’t use player to group the events anymore. Now it groups on the source ability. Makes no sense to group on the player.

[jeffwadsworth]

Also, The Gitrog Monster works fine now.

[jeffwadsworth]

Checked the other ZONE_CHANGE_GROUP cards and they work fine as well.

[JayDi85]

BatchGameEvent can help