[Zope-dev] Re: How to publish Zope2 products on PyPI

[Martin Aspeli]

Dieter Maurer wrote:
> During our latest discussion to put my most important Zope2 products
> into a public repository, I have promissed to publish them on
> PyPI instead. Yesterday, I started work to fulfill this promiss
> and carefully read the PyPI related documentation -- to find
> out, that it is not easy to publish Zope2 products.
> 
> As the name suggests, PyPI is for Python packages.
> And Zope2 products rightfully are no Python packages:
> 
>    When a Zope instance starts, it does potentially
>    expensive things for its products.
> 
>    I have tiny Zope instances with a few inexpensive products
>    that start within a few seconds. And I have huge
>    Zope instances with lots of products which parse huge
>    XML files or have large message catalogs
>    and take half to one minute to start.
> 
>    Definitely, I do not want that all my Zope
>    instances use the same products installed
>    via "setuptools" somewhere under the central "site-packages".
> 
> 
> My current ideas towards a solution:
> 
>   We define a package prefix for Zope2 products, e.g. "zope2.products".

-1 to more magic namespaces!

>   Zope2 products are published to PyPI as "<prefix>.<productname>".

We already have that. Products.*.

Basically, on Zope 2 trunk (and in 2.11), we've made 
Products/__init__.py declare Products.* as a namespace package. That 
means that you can package up an egg that uses this namespace package 
and upload it to the cheese shop. Several of the Plone packages, e.g. 
http://cheeseshop.python.org/pypi/Products.CMFDynamicViewFTI/3.0, do this.

>   We extend the Zope2 configuration with an option "additional-products"
>   which lists the products used by the instance that are not
>   at a standard place -- such as those installed by "setuptools"

I really don't see the need for this kind of complication. I would never 
install a Products.* package into the global python interpreter. That's 
a recipe for pain and incompatibility. Instead, I'd use zc.buildout or 
virtualenv to have a sandbox for these eggs.

see http://plone.org/documentation/tutorial/buildout and 
http://martinaspeli.net/articles/python-package-management.

Secondly, we already have something like additional-products, in that 
for packages outside the Products.* namespace, we do not automatically 
read ZCML, call initialize() and so on. Instead, we require that:

  - the package's ZCML is explicitly pulled in, either via a ZCML slug, 
or via an include from another ZCML file which is explicitly (or 
implicitly, if it's in Products/*) parsed.

  - the package uses the <five:registerPackage /> directive to declare 
the package a Zope 2 product, which causes its initialize() function to 
be called at the appropriate time.

Note that anything in Products.*, whether eggs in that namespace package 
or plain directories in e.g. $INSTANCE_HOME/Products, behave as they 
always have: ZCML is auto-loaded by Five, initialize() is always called.

Martin

-- 
Acquisition is a jealous mistress