[FM3] IncompatibleImprovements setting (Was: Re: Preparing for releasing 2.3.26 - any feedback?)

[Daniel Dekany <dd...@freemail.hu>]

Tuesday, March 14, 2017, 11:49:48 PM, Denis Bredelet wrote:

[snip]
> For FreeMarker 3 should we revert backward compatibility option? Instead of setting:
> incompatible_improvements = 3.1.0
> the developer will specify:
> compatible_version = 3.1.0
> \u2026 And any incompatible improvements in version 3.1.1 or more will not be used.

That's what incomptibleImprovements do as well. What exactly is the
difference?

> That way the default is to use all the latest improvements rather
> than just backward-compatible ones.

That defeats the purpose of incomptibleImprovements, which is that we
can fix/improve things despite that they slightly break backward
compatibility. Because there's no default value (or, in 2.3.x there
is, but it's the possible most conservative value, 2.3.0), you can
safely upgrade FreeMarker under a project, as no new
non-backward-compatible changes will be activated, since upgrading
FreeMarker doesn't increase your incompatibleImprovements value. In
case someone starts a new project, he will most certainly use the
highest possible incomptibleImprovements at the time he started
development, so new projects will benefit from said
fixes/improvements. Existing project can of course also review what
changes these are, and increase the incompaibleImprovements, but it's
their decision if they are willing to invest into that and if when.
What we try to avoid is that people are using ancient versions because
of the risk of breaking the existing application.

> As an example with this scheme exp?interpret would work as it
> should in version 2.3.26 by default, instead of requiring a flag to work properly.

BTW, in FM3 the lowest supported incompatibleImprovemetns is 3.0.0.
(Obviously, as the minimum goal of FM3 is getting rid of that 15 years
of backward compatibility baggage.)

> What do you think?
>
> \u2014 Denis. 
>
> Cheers,
>
> Woonsan
>
>
> Also tell if you want some additional changes to get into this
> release.
>
> Also, if you can, check if this version breaks anything on your
> systems (this is *not* the final 2.3.26 yet, but almost):
> https://dist.apache.org/repos/dist/dev/incubator/freemarker/engine/2.3.26-nightly-incubating/binaries/
>
> I hope that after some more small changes I can upload the real 2.3.26
> for voting.
>
> --
> Thanks,
> Daniel Dekany
>

-- 
Thanks,
 Daniel Dekany