Version-independent save games

[hobbesjaap]

Describe the problem
As mentioned in this topic on the AGS Forums it would be great to improve the save system in AGS. Right now, when I update a game / change something in the game, the saved games don't work anymore. This makes bug-fixing or expanding a game rather tiresome for players, since they have to start from scratch.

Suggested change
First change: As Crimson Wizard mentions, the main issue is that AGS lacks a system "of reliable identification of game objects within the game data."

This has multiple underlying issues (which go way beyond my programming knowledge). By resolving these issues, saved games would continue to work even if a game is modified/changed/expanded.

Second change: In a more severe situation (where someone changes the game beyond recognition) we could also consider a system where AGS gives a warning "This save file differs too much from this game - are you sure you wish to proceed?" and then loads the saved game, ignoring all the errors present and only restoring "what it can".

[ivan-mogilko]

An update on this problem: following minimal solution has been implemented in v3.6.2 of the engine (and ported to v4.0 as well):

• Support for restoring saves with less data, and running "validation" callback in user script: Support reading saves from older game version #2489
• A function that prescans and tests saves for compatibility without actually overwriting current data: Script API: Prescan saves and test for validity #2579

Unfortunately, in this ticket the task is defined rather vaguely. But formally it is not fully covered by aforementioned changes.
We may keep it for the reference until there's a ticket with more thorough requirements.