D versionning

[Adam Wilson]

On Fri, 13 Jul 2012 09:58:22 -0700, Jonathan M Davis <jmdavisProg at gmx.com>  
wrote:

> On Thursday, July 12, 2012 18:49:16 deadalnix wrote:
>> The system adopted in PHP works with a 3 number version. The first
>> number is used for major languages changes (for instance 4 > 5 imply
>> passing object by reference when it was by copy before, 5 > 6 switched
>> the whole thing to unicode).
>>
>> The second number imply language changes, but either non breaking or
>> very specific, rarely used stuff. For instance 5.2 > 5.3 added GC,
>> closures and namespace which does not break code.
>>
>> The last one is reserved for bug fixes. Several version are maintained
>> at the same time (even if a large amount of code base is common, so bug
>> fixes can be used for many version at the time).
>
> You know, the more that I think about this, the less that I think that  
> this
> idea buys us anything right now. This sort of versioning scheme is great  
> when
> you need to maintain ABI compatibility, when you want to restrict adding  
> new
> features to only specific releases, and when you want to specify which  
> kind of
> release is allowed to introduce breaking changes, but it doesn't really  
> fit
> where D is right now.
>
> We're not at a point where we're trying to maintain ABI compatibility,  
> so that
> doesn't matter, but the major reason that this wouldn't buy us much is  
> that
> almost all breaking changes are not introduced by new features or major
> redesigns or whatnot. They're introduced by bug fixes (either by the fix
> themselves changing how things work, since the way they worked was  
> broken -
> though code may have accidentally been relying on it - or because a  
> regression
> was introduced as part of the fix). Once in a while, fleshing out a  
> partially
> working feature breaks some stuff (generally causing regressions of some  
> kind),
> but most of it's bug fixes, and if it's due to an incomplete feature  
> being
> fleshed out, then fewer people are going to be relying on it anyway. The  
> few
> new features that we've added since TDPL have not really been breaking
> changes. They've added new functionality on top of what we've already  
> had.
>
> The few cases where we _do_ introduce breaking changes on purpose, we do  
> so
> via a deprecation path. We try and inform people (sometimes badly) that a
> feature is going to be changed, removed, or replaced - that it's been
> scheduled for deprecation. Later, we deprecate it, and even later, we  
> remove
> it. In the case of Phobos, this is fairly well laid out, with things  
> generally
> being scheduled for deprecation for about 6 months, and deprecated stuff
> sticking around for about 6 months before being removed. In the case of  
> the
> compiler, it's less organized.
>
> Features generally don't actually get deprecated for a long time after  
> it's
> been decided that they'll be deprecated, and they stick around as  
> deprecated
> for quite a while. Newer functionality which breaks code is introduced  
> with -w
> (or in one case, with a whole new flag: -property) so that programmers  
> have a
> chance to switch to it more slowly rather than breaking their code  
> immediately
> when the next release occurs. Later, they'll become part of the normal  
> build
> in many cases, but that generally takes forever. And we don't even add  
> new
> stuff like that very often, so even if you always compile with -w, it  
> should be
> fairly rare that your code breaks with a new release due to something  
> like
> that being added to -w. The last one that I can think of was disallowing
> implicit fallthrough on case statements.
>
> So, in general, when stuff breaks, it's on accident or because how things
> worked before was broken, and some code accidentally relied on the buggy
> behavior. Even removing opEquals, opCmp, toHash, and toString will be  
> done in
> a way which minimizes (if not completely avoids) immediate breakage.  
> People
> will need to change their code to work with the new scheme, but they  
> won't
> have to do so immediately, because we'll find a way to introduce the  
> changes
> such that they're phased in rather than immediately breaking everything.

And if we had a dev branch we could have rolled Object const into it and  
let it broken there without affecting stable.

We have no stable release because we only have one branch, dev. To have a  
stable release you must first have a branch you consider to be stable.

Major changes are rolled INTO stable from dev once they become stable.  
Another term for stable is staging if that language helps you understand  
the concept better.

Stable does NOT and NEVER will mean bug free.

It means that we think this code has generally been well tested and works  
in most cases and we promise not to break it with big changes. Note the  
last part, we promise not to break it with big changes (such as object  
const). Thats how you create a stable release, first you must promise not  
to break it severly. Currently we don't make that promise.

But just because we don't make that promise does not mean that we cannot  
or should not make that promise. That promise is highly valuable to the  
community at large.

> All that being the case, I don't know what this proposal actually buys  
> us. The
> very thing that causes the most breaking changes (bug fixes) is the  
> thing that
> still occurs in every release.
>
> - Jonathan M Davis


-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/