[Zope3-dev] Re: zope.annotation dependency to zope.app.container.contained

[Philipp von Weitershausen]

Roman Joost wrote:
> we're doing some dependency checking at gocept and I discovered that
> zope.annotation depends on zope.app.container in its factory.
> 
> What shall we do with this dependency to zope.app.container? Moving this
> factory to zope.app is probably not the best solution.

To be clear, zope.annotation doesn't depend on zope.app, it depends on 
zope.app.container which is its own package and egg (and in fact, 
zope.annotation's dependencies are refreshingly few). The real problem 
is that zope.app.container depends on a whole bunch of other things. The 
question is why.


Michael Howitz's email about ISite demonstrates a recurring problem:

There are several packages that do two things. One one hand they define 
concepts (IContained, ISite, etc.) and a little bit of machinery 
(contained(), getSite(), etc.) to deal with these concepts. On the other 
hand they also provide full-fledged implementations. Those 
implementations are the ones that end up introducing lots of 
dependencies (because they involve security, events, persistency, etc. etc.)

Perhaps it makes sense to factor the *concepts* and the light-weight 
helpers (contained(), getSite(), etc.) out to separate packages, e.g.:

  * zope.container
  * zope.componentsite
  * ...

There wouldn't even be a BBB problem, we could just leave import the 
interfaces and helpers from the new location and leave them there 
forever. That way, packages won't break if they still depend on 
zope.app.container and zope.app.component.


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