[ZODB-Dev] RFC: Proposed backward-compatibility policy

[Jim Fulton]

Jeremy Hylton wrote:
> On Wed, 27 Oct 2004 12:53:44 -0400, Jim Fulton <jim at zope.com> wrote:
> 
>>2. Backward compatibility support will be limited. When we make a
>>    change that would require a change in software or data, we'll add
>>    code to support the old software or data, but we will also add
>>    code to generate deprecation warnings when that support code is
>>    used.  The deprecation warnings will say specifically when the
>>    backward-compatibility support will go away.  This time will
>>    usually be expressed as a release number at least two feature
>>    releases past the next feature release. (For example, if the next
>>    feature release is release 3.4, then the backward compatibility
>>    support would not be removed any sooner than release 3.6.)  In
>>    other words, we will limit the time extent of backward
>>    compatibility support, but we will give plenty of warning.
> 
> 
> How does this apply in the near term?  The cat is already out of the
> bag for 3.3,

Right, so this applies to 3.4.

 > which probably isn't fully backwards compatible.

I think we should look at backward compatabilities on a
case-by-case basis and we may very well want to treat some of
them as bugs.

 > Would
> you consider those bugs that would be fixed in a 3.3 maintenance
> release? 

Potentially. We need to look at the specifics.

 > For example, I don't think the ZEO protocol for 3.3 isn't
> compatible with the ZEO protocol for 3.2.  In addition to data and
> code, it might be worthwhile to say something in the policy about zeo
> protocol compatibility.

Perhaps.

> 
> 
>>3. It is very important to catch backward compatibility problems
>>    during development of new releases.   In particular, it is
>>    important to test new ZODB releases before they are released in
>>    final form.  If a backward-compatibility problem is found before
>>    the final release, it will be considered a bug and will be fixed
>>    (by adding backward compatibility support) if at all possible
>>    before the final release.  After the final release, we may choose
>>    not to bother to fix backward-compatibility problems.  Consumers of
>>    ZODB have a right to backward compatibility, but they also have a
>>    responsibility to test ZODB against their applications during the
>>    beta release cycle (or sooner) to make sure their applications
>>    work.
> 
> 
> Does this mean that consumers who depend on subtle features are out of
> luck if they don't test the alphas or betas? 

Yes

 > I think that may be the
> only practical thing to do.  There are too many under-documented
> corners of ZODB to be thorough about testing without help from users.

Exactly.

Jim

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