five.intid 0.2.1

Zope2 support for zope.app.intid

Introduction

This package makes it possible to use zope.app.intid (and consequentually other packages that rely on it such as zope.app.keyreference) in a Zope2 environment.

Usage

First, let make sure the ofs utility provides the interface:

>>> from zope.app.intid.interfaces import IIntIds
>>> from five.intid import site
>>> import five.intid.tests as tests
>>> from zope.interface.verify import verifyObject
>>> from zope.component import getAllUtilitiesRegisteredFor
>>> from zope.app.component.hooks import setSite
>>> tests.setUp(self.app)

Content added before the utility won’t be registered(until explicitly called to). We’ll set some up now for later

>>> tests.manage_addSimpleContent(self.folder, 'mycont1', "My Content")
>>> content1 = self.folder.mycont1

five.intid.site has convenience functions for adding, get and removing an IntId utility: add_intid, get_intid, del_intid.

You can install the utility in a specific location:

>>> site.add_intids(self.folder)
>>> folder_intids = site.get_intids(self.folder)
>>> verifyObject(IIntIds, folder_intids)
True

You can tell add_intids to find the site root, and install there. It will be available everywhere:

>>> site.add_intids(self.folder, findroot=True)
>>> root_intids = site.get_intids(self.app)
>>> root_intids
<...IntIds ...>
>>> folder_intids is root_intids
False

And finally, do a remove:

>>> site.del_intids(self.folder, findroot=True)
>>> site.get_intids(self.app)
Traceback (most recent call last):
...
ComponentLookupError: (<InterfaceClass zope.app.intid.interfaces.IIntIds>, '')

Before we look at intid events, we need to set the traversal hook. Once we have done this, when we ask for all registered Intids, we will get the utility from test folder:

>>> setSite(self.folder)
>>> tuple(getAllUtilitiesRegisteredFor(IIntIds))
(<...IntIds ...>,)

When we add content, event will be fired to add keyreference for said objects the utilities (currently, our content and the utility are registered):

>>> from five.intid.lsm import USE_LSM
>>> tests.manage_addSimpleContent(self.folder, 'mycont2', "My Content")
>>> content2 = self.folder.mycont2
>>> intid = site.get_intids(self.folder)
>>> if USE_LSM:
...     len(intid.items()) == 1
... else:
...     len(intid.items()) == 2
True

Pre-existing content will raise a keyerror if passed to the intid utility:

>>> intid.getId(content1)
Traceback (most recent call last):
...
KeyError: <SimpleContent at /test_folder_1_/mycont1>

We can call the keyreferences, and get the objects back:

>>> if USE_LSM:
...     intid.items()[0][1]()
... else:
...     intid.items()[1][1]()
<SimpleContent at /test_folder_1_/mycont2>

we can get an object’s intid from the utility like so:

>>> ob_id = intid.getId(content2)

and get an object back like this:

>>> intid.getObject(ob_id)
<SimpleContent at /test_folder_1_/mycont2>

these objects are aquisition wrapped on retrieval:

>>> type(intid.getObject(ob_id))
<type 'ImplicitAcquirerWrapper'>

We can even turn an unwrapped object into a wrapped object by resolving it from it’s intid, also the intid utility should work even if it is unwrapped:

>>> from Acquisition import aq_base
>>> resolved = intid.getObject(intid.getId(aq_base(content2)))
>>> type(resolved)
<type 'ImplicitAcquirerWrapper'>
>>> unwrapped = aq_base(intid)
>>> unwrapped.getObject(ob_id) == resolved
True
>>> unwrapped.getId(content2) == ob_id
True

When an object is added or removed, subscribers add it to the intid utility, and fire an event is fired (zope.app.intid.interfaces.IIntIdAddedEvent, zope.app.intid.interfaces.IIntIdRemovedEvent respectively).

five.intid hooks up these events to redispatch as object events. The tests hook up a simple subscriber to verify that the intid object events are fired (these events are useful for catalogish tasks).

>>> tests.NOTIFIED[0]
'<SimpleContent at mycont2> <...IntIdAddedEvent instance at ...'

Registering and unregistering objects does not fire these events:

>>> tests.NOTIFIED[0] = "No change"
>>> uid = intid.register(content1)
>>> intid.getObject(uid)
<SimpleContent at /test_folder_1_/mycont1>

>>> tests.NOTIFIED[0]
'No change'

>>> intid.unregister(content1)
>>> intid.getObject(uid)
Traceback (most recent call last):
...
KeyError: ...

>>> tests.NOTIFIED[0]
'No change'

Renaming an object should not break the rewrapping of the object:

>>> self.setRoles(['Manager'])
>>> folder.mycont2.meta_type = 'Folder' # We need a metatype to move
>>> folder.manage_renameObject('mycont2','mycont_new')
>>> moved = intid.getObject(ob_id)
>>> moved
<SimpleContent at /test_folder_1_/mycont_new>

Nor should moving it:

>>> from OFS.Folder import manage_addFolder
>>> manage_addFolder(self.folder, 'folder2', "folder 2")
>>> cut = folder.manage_cutObjects(['mycont_new'])
>>> ignore = folder.folder2.manage_pasteObjects(cut)
>>> moved = intid.getObject(ob_id)
>>> moved
<SimpleContent at /test_folder_1_/folder2/mycont_new>
>>> moved.aq_parent
<Folder at /test_folder_1_/folder2>

Let’s move it back:

>>> cut = folder.folder2.manage_cutObjects(['mycont_new'])
>>> ignore = folder.manage_pasteObjects(cut)
>>> folder.manage_renameObject('mycont_new','mycont2')

We can create an object without acquisition so we can be able to add intid to it :

>>> from five.intid.tests import DemoPersistent
>>> demo1 = DemoPersistent()
>>> demo1.__parent__ = self.app
>>> from zope.event import notify
>>> from zope.app.container.contained import ObjectAddedEvent
>>> notify(ObjectAddedEvent(demo1))
>>> nowrappid = intid.getId(demo1)
>>> demo1 == intid.getObject(nowrappid)
True

This is a good time to take a look at keyreferences, the core part of this system.

Key References in Zope2

Key references are hashable objects returned by IKeyReference. The hash produced is a unique identifier for whatever the object is referencing(another zodb object, a hook for sqlobject, etc).

object retrieval in intid occurs by calling a key reference. This implementation is slightly different than the zope3 due to acquisition.

The factories returned by IKeyReference must persist and this dictates being especially careful about references to acquisition wrapped objects as well as return acq wrapped objects as usually expected in zope2.

>>> ref = intid.refs[ob_id]
>>> ref
<five.intid.keyreference.KeyReferenceToPersistent object at ...>

The reference object holds a reference to the unwrapped target object and a property to fetch the app(also, not wrapped ie <type ‘ImplicitAcquirerWrapper’>):

>>> ref.object
<SimpleContent at mycont2>

>>> type(ref.object)
<class 'Products.Five.tests.testing.simplecontent.SimpleContent'>

>>> ref.root
<Application at >

Calling the reference object (or the property wrapped_object) will return an acquisition object wrapped object (wrapped as it was created):

>>> ref.wrapped_object == ref()
True

>>> ref()
<SimpleContent at /test_folder_1_/mycont2>

>>> type(ref())
<type 'ImplicitAcquirerWrapper'>

The resolution mechanism tries its best to end up with the current request at the end of the acquisition chain, just as it would be under noraml circumstances:

>>> ref.wrapped_object.aq_chain[-1]
<ZPublisher.BaseRequest.RequestContainer object at ...>

The hash calculation is a combination of the database name and the object’s persistent object id(oid):

>>> ref.dbname
'unnamed'

>>> hash((ref.dbname, ref.object._p_oid)) == hash(ref)
True

>>> tests.tearDown()

Acquisition Loops

five.intid detects loops in acquisition chains in both aq_parent and __parent__.

Setup a loop:

>>> import Acquisition
>>> class Acq(Acquisition.Acquirer): pass
>>> foo = Acq()
>>> foo.bar = Acq()
>>> foo.__parent__ = foo.bar

Looking for the root on an object with an acquisition loop will raise an error:

>>> from five.intid import site
>>> site.get_root(foo.bar)
Traceback (most recent call last):
...
AttributeError: __parent__ loop found

Looking for the connection on an object with an acquisition loop will simply return None:

>>> from five.intid import keyreference
>>> keyreference.connectionOfPersistent(foo.bar)

FSObjects

The FSObjects from CMFCore can have pickling problems if the five.intid event handlers end up adding an FSObject to a connection. As such they’re omitted.

>>> from zope import interface, component
>>> from five.intid import keyreference
>>> component.getSiteManager().registerAdapter(
...     factory=keyreference.connectionOfPersistent)

>>> from Products.CMFCore import FSPythonScript
>>> foo = FSPythonScript.FSPythonScript('foo', __file__)
>>> self.app._setObject('foo', foo)
'foo'

>>> keyref = keyreference.KeyReferenceToPersistent(self.app.foo)
Traceback (most recent call last):
...
UnsettableAttributeError: <FSPythonScript at foo>
>>> foo in self.app._p_jar._registered_objects
False

Note: I’m not sure whether the real problem here is in five.intid or in FSObject. FSObject implements IPersistent so it seems like instances should be addable to connections without error so it can be argued that the error is in FSObject. On the other hand, FSObject instances were probably only ever intended to be used in DirectoryViews in CMF skins. As such it could also be argued that five.intid is behaving improperly by aggressively trying handle events for all objects implementing IPersistent.

There’s another related problem with DirectoryView objects that isn’t covered here. DirectoryView stores instances of Persistent classes (like FSPageTemplate) in a global registry and thus counts on those instances never being added to a ZODB connection. When the five.intid event handlers add such objects to a ZODB connection, the retrieval from global state could result in an instance from a closed connection being de-ghosted raising a ConnectionStateError.

Changelog

0.2.1 - Nov 05, 2008

• Avoid unnecessary adapter lookups in __cmp__ as __cmp__ is called rather often and is performance sensitive. Cumulative time now 0.080 vs previous 1.820 for 6000 compares when profiling. [tesdal]

• Avoid redundant __cmp__ calls in BTree traversal. [tesdal]

0.2.0 - May 20, 2008

• Cleanup documentation a little bit so it can be used for the pypi page. [wichert]

• Many changes by many people. [alecm, hannosch, maurits, mborch, reinout, rockt, witsch]

0.1.4 - November 11, 2006

• First public release. [brcwhit]