[Zope-dev] Re: zcml entry points

[Wichert Akkerman]

Martin Aspeli wrote:
> Fred Drake wrote:
>   
>> On 10/17/07, Wichert Akkerman <wichert at wiggy.net> wrote:
>>     
>>> A common issue we are seeing is that we have eggs depending on each
>>> other, but they still need to load the zcml from those dependencies
>>> somehow. As a temporary solution to play with the concept I added
>>> something simple to the plone.recipe.zope2instance buildout recipe.
>>>       
>> What's the problem you're seeing?  I'm not sure what you're trying
>> to
>> solve.  ZCML includes work just fine in the egg world.
>>
>> As long as you're referring to packaged ZCML using
>> package="package.name" in your <include> and <includeOverrides>
>> directives, all is good.
>>     
>
> The main win, IMHO, is to avoid the requirement for people to install 
> slugs for third party products. Slugs suck - they are confusing to 
> explain and people forget them all the time. Buildout makes it a bit 
> easier, but it's still not a terribly good solution.
>
> For example, say you want to install oi.plum. You need to add the
> line 
> 'oi.plum' twice - once under 'eggs' and once under 'zcml' in your 
> buildout.cfg. Forget the latter, and the package doesn't work
> properly 
> (or at all).
>   

I see a different win. At the moment we are declaring dependencies in
two places: in the egg information and in the zcml files. For every
package I need I need to make sure its zcml is loaded, which means I
need to have a meta.zcml, configure.zcml and overrides.zcml which load
the meta, configure and overrides from all packages I depend on. I also
need to inspect every package I depend on to check if they have a meta,
configure or overrides.zcml, which in my humble opinion should be just
an implementation detail that I, as someone who is just using the zope
stack/framework, should not need to know about. Multiply that with the
number of dependencies you see in zope.* and you see this becomes very
unwieldy.

So I turned things around: if I state in my egg information that I
require another package that means I need to have that package
available and functional. Which suggests that its zcml has to be loaded
before mine. And that is exactly what I am doing: adding an entry point
that allows a package to say "in order to function I need to have these
zcml files loaded".

Wichert.

-- 
Wichert Akkerman <wichert at wiggy.net>   It is simple to make things.
http://www.wiggy.net/                  It is hard to make things simple.