isotoma.egglayer 0.0.4

Utility for packaging things as eggs without setuptools

Python Egg Layer

This package provides python classes for building Python packages on the fly. Why don’t we use setuptools? Well we needed to generate the egg dynamically from a Django view and not generate the temp files. Why on earth would you want to dynamically generate a python package? Policy is really best injected into Plone through GenericSetup. But a lot of the policy depends on settings in Buildout or other deployment systems. Simple python eggs are trivial to generate, so we decided to see how well it worked to generate policy eggs from our configuration management tools.

Features

Automatic namespacing

If your package is called foo.bar.baz then foo/__init__.py and foo/bar/__init__.py will automatically contain the pkg_resources magic needed for namespacing, and the setup.py will define all the namespace packages.

Automatic z3c.autoinclude

If you build a Plone package, it will automatically be advertised to Plone using z3c.autoinclude.

Hello, world!

Before we can start building an egg we need 3 things: The package name, version and a file-like object to write to. This can be StringIO, a file or even a Django HTTPResonse:

from isotoma.egglayer import Package
p = Package(open("test.zip", "w"), "test.package", "1.0")

You don’t need to worry about directories. You just add files:

p.add("test/package/__init__.py", "print 'Hello, world!'")

Any files you add are tracked so that the SOURCES.txt for the egg is correct.

When you have finished adding content to the package you call the close() method. This will generate the egg-info directory and a setup.py:

p.close()

Python will automatically call close() during __del__ if you do not.

Dynamically generating packages from Django

We set up a new view subclass like this:

from django.views.generic import View
from django.http import HttpResponse
from django import template
from isotoma.egglayer import Package

class MyCustomizedEgg(View):

    def get(self, request, *args, **kwargs):
        response = HttpResponse(content_type="application/zip")
        response['Cache-Control'] = 'no-cache'
        response['Content-Disposition'] = 'filename=test.customegg-1.0.zip'

        p = Package(response, 'test.customegg', '1.0')
        p.add("test/customegg/foo.py", "print "hello world")
        p.close()

        return response

Because a HttpResonse is a file like object we can wire it up directly as the output of the Package object. You can set a Cache-Control header to stop the egg being cached while you are testing, but your final code shouldn’t require it. The Content-Disposition header allows your browser to suggest a sensible filename when saving your dynamically generated package. If you are using this view from a tool like pip or buildout it may or may not care about this header.

(Obviously you will need to wire this into urls.py - see the wonderful Django documentation for how to do this).

Changelog

0.0.4 (2012-01-31)

• Add a helper for creating properties.xml files.

0.0.3 (2011-12-21)

• Make plone xmlns available by default in configure.zcml

0.0.2 (2011-12-14)

• Add a helper for generating propertiestool.xml:

  p = Profile("default")
  p.propertiestool.set("site_properties", "someproperty", "somevalue")
  pkg.add_profile(p)

• Add a helper for generated records in registry.xml:

  p = Profile("default")
  p.registry.set("plone.app.theming.interfaces.IThemeSettings.hostnameBlacklist", ["localhost"])
  pkg.add_profile(p)

0.0.1 (2011-12-14)

• Some basic abstractions to help generating Plone GenericSetup profiles:

  p = Profile("default")
  p.dependencies.extend([
       "my.other.egg:default",
       ])
  pkg.add_profile(p)

• Can inject raw zcml into conficture.zcml:

  pkg.zcml_stanza.apend('<i18n:registerTranslations directory="locales"/>')

• __init__.py will be automatically created for the root non-namespaced folder in your project. For plone project it will have a no-op initialize() that is referenced by configure.zcml.

0.0.0 (2011-12-09)

• Initial version.