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

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