[Freeciv-Dev] Re: backward compatability of saved games

[Gregory Berkolaiko <Gregory.Berkolaiko@xxxxxxxxxxxxx>]

On Mon, 28 Jun 2004, Jason Dorje Short wrote:

> In the past we have discussed how gen-eff may necessitate the breaking
> of savegame backward compatibility.  I don't think this is true, but it
> does bring up the idea...
>
> There is a _lot_ of stuff in savegame.c to preserve backward
> compatibility.  Nobody really knows how far back compatibility goes.
> When writing new code we preserve compatibility with the previous
> savegame format but we could easily break compatibility with even older
> savegame formats and not even know it (for this reason I'm afraid to
> change anything in savegame.c).
>
> There is something to be said for a one-time breaking of compatibility.
>   It would allow the removal of hundreds of lines of code in savegame.c
> and the logic could be cleaned up so that we actually understand it.  We
> could then mark a definite point that savegames must be compatible with,
> and make some publically available savegames that can be used for
> testing of future code.
>
> However the new compatibility period wouldn't kick in until the next
> release; until then we would be free to break compatibility some more.
> In the meantime we should fix many of the ruleset incompatibilities
> (changing the ruleset breaks savegame compatibility unless you're really
> careful, in part because the savegame depends unnecessarily on the order
> of elements in the ruleset).
>
> I'm not sure if I'm in favor of this idea.  It is really a way to
> simplify the code at the expense of the user.  However because the code
> is simpler it will be end up with faster, less buggy development, so the
> user will benefit as well.
>
> What do other people think?

We can safely break the compatibility now because it was already broken
about a week ago by introducing a new unit into the ruleset.

Making savegames robust wrt ruleset changes would actually be some work
(the easiest would be to save the ruleset info in the game I guess).

G.