Implementing a simple dexterity content type for plone 4

Question

I have a very frustrating start learning Plone development. I would like to develop a dexterity based content type for Plone 4. I'm an experienced python developer, having some knowledge of Zope and Grok, being rather new to buildout. That said, I read "Professional Plone 4 Development" by Martin Aspeli, but quite some version information in the book seems to be outdated.

Using buildout I was able to get a Plone instance up and running. ZopeSkel is installed but when I try to create a new package, I get an error like this:

**************************************************************************
**  Your new package supports local commands.  To access them, change
**  directories into the 'src' directory inside your new package.
**  From there, you will be able to run the command `paster add
**  --list` to see the local commands available for this package.
**************************************************************************


ERROR: No egg-info directory found (looked in ./domma.voucher/./domma.voucher.egg-info, ./domma.voucher/bootstrap.py/domma.voucher.egg-info, ./domma.voucher/bootstrap.pyo/domma.voucher.egg-info, ./domma.voucher/buildout.cfg/domma.voucher.egg-info, ./domma.voucher/CHANGES.txt/domma.voucher.egg-info, ./domma.voucher/CONTRIBUTORS.txt/domma.voucher.egg-info, ./domma.voucher/docs/domma.voucher.egg-info, ./domma.voucher/domma/domma.voucher.egg-info, ./domma.voucher/README.txt/domma.voucher.egg-info, ./domma.voucher/setup.cfg/domma.voucher.egg-info, ./domma.voucher/setup.py/domma.voucher.egg-info, ./domma.voucher/src/domma.voucher.egg-info)

If I try to run paster from within the given directory, it tells me, that the command "add" is not know. I tried different versions of ZopeSkel and tried the raw plone templates and also zopeskel.dexterity. The output changes slightly depending on version and template, but the result remains the same.

Obvisouly Plone development seems to be very sensible to version changes, which makes older documentation quite useless. http://plone.org/products/dexterity/documentation/manual/developer-manual tells me, that it has been updated last time 1114 ago.

Could somebody give me a starting point to develop a very simple dexterity content type for Plone 4 which really works?

Answer 1

For what it's worth, whilst there are a few newer versions of some packages, Professional Plone 4 Development is current with Plone 4.1. I would suggest you use it, and start from its sample code. Don't try to arbitrarily upgrade things until you know you have a working starting point, and you should be OK.

Answer 2

I was able to create a new Plone 4.1.4 site with a new Dexterity content-type using this buildout. This should not be an official answer but pasting the configuration to a volatile service like pastebin is not an option for permanent documentation.

# buildout.cfg file for Plone 4 development work
# - for production installations please use http://plone.org/download
# Each part has more information about its recipe on PyPi
# http://pypi.python.org/pypi 
# ... just reach by the recipe name
[buildout]
parts =  
    instance
    zopepy
    i18ndude
    zopeskel
    test
#    omelette

extends = 
    http://dist.plone.org/release/4.1-latest/versions.cfg
    http://good-py.appspot.com/release/dexterity/1.2.1?plone=4.1.4

# Add additional egg download sources here. dist.plone.org contains archives
# of Plone packages.
find-links =
    http://dist.plone.org/release/4.1-latest
    http://dist.plone.org/thirdparty

extensions = 
    mr.developer
    buildout.dumppickedversions

sources = sources

versions = versions

auto-checkout = 
    nva.borrow

# Create bin/instance command to manage Zope start up and shutdown
[instance]
recipe = plone.recipe.zope2instance
user = admin:admin
http-address = 16080
debug-mode = off
verbose-security = on
blob-storage = var/blobstorage
zope-conf-additional = %import sauna.reload

eggs =
    Pillow
    Plone
    nva.borrow
    sauna.reload
    plone.app.dexterity

# Some pre-Plone 3.3 packages may need you to register the package name here in 
# order their configure.zcml to be run (http://plone.org/products/plone/roadmap/247)
# - this is never required for packages in the Products namespace (Products.*)
zcml =
#    nva.borrow
    sauna.reload


# zopepy commands allows you to execute Python scripts using a PYTHONPATH 
# including all the configured eggs
[zopepy]
recipe = zc.recipe.egg
eggs = ${instance:eggs}
interpreter = zopepy
scripts = zopepy

# create bin/i18ndude command
[i18ndude]
unzip = true
recipe = zc.recipe.egg
eggs = i18ndude

# create bin/test command
[test]
recipe = zc.recipe.testrunner
defaults = ['--auto-color', '--auto-progress']
eggs =
    ${instance:eggs}

# create ZopeSkel and paster commands with dexterity support
[zopeskel]
recipe = zc.recipe.egg
eggs =
    ZopeSkel<=2.99
    PasteScript
    zopeskel.dexterity<=2.99
    ${instance:eggs}

# symlinks all Python source code to parts/omelette folder when buildout is run
# windows users will need to install additional software for this part to build 
# correctly.  See http://pypi.python.org/pypi/collective.recipe.omelette for
# relevant details.
# [omelette]
# recipe = collective.recipe.omelette
# eggs = ${instance:eggs}

# Put your mr.developer managed source code repositories here, see
# http://pypi.python.org/pypi/mr.developer for details on the format of
# this part
[sources]
nva.borrow = svn https://novareto.googlecode.com/svn/nva.borrow/trunk

# Version pindowns for new style products go here - this section extends one 
# provided in http://dist.plone.org/release/
[versions]

Answer 3

http://pigeonflight.blogspot.com/2012/01/dexterity-development-quickstart-using.html offers a nice quickstart. The most current Dexterity docs are at http://dexterity-developer-manual.readthedocs.org/en/latest/index.html. Yes, this is a little bit of a moving target, documentation-wise, not so much due to Dexterity, which is stable and in production, but mainly because Zopeskel is under heavy development/modernization right now. Sorry about that.

Answer 4

From [https://github.com/collective/templer.plone/blob/master/README.txt][1]

Templer cannot coexist with old ZopeSkel in the same buildout, or Python virtualenv.

Otherwise you will encounter the following error when trying to create packages::

  IOError: No egg-info directory found (looked in ./mycompany.content/./mycompany.content.egg-info, ....

Templer is the latest incarnation of ZopeSkel(version 3). I am not sure what version of ZopeSkel you have or if you have mixed versions installed in buildout or virtualenv. But the conflicting installation of ZopeSkel is likely the culprit.

I would start from scratch and recreate vitualenv and just install the latest version of ZopeSkel 2 via buildout. ZopeSkel 3 or Templer is still in heavy development and not all templates have been migrated.