Make the ZODB-dependent functest of persistent.wref into standalone doctests.

Put them inside ZODB/tests in anticipation of separating persistent from
ZODB.

src/ZODB/tests/testPersistentWeakref.py

+##############################################################################
+#
+# Copyright (c) 2003 Zope Foundation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""ZODB-based (functional) tests persistent weakrefs
+"""
+__docformat__ = "reStructuredText"
+
+
+
+def test_weakrefs_functional():
+    """Persistent weak references
+
+    Persistent weak references are used much like Python weak
+    references.  The major difference is that you can't specify an
+    object to be called when the object is removed from the database.
+
+    Here's an example. We'll start by creating a persistent object and
+    a reference to it:
+
+    >>> from persistent.wref import WeakRef
+    >>> import persistent, ZODB.tests.MinPO
+    >>> import ZODB.tests.util
+    >>> ob = ZODB.tests.MinPO.MinPO()
+    >>> ref = WeakRef(ob)
+    >>> ref() is ob
+    True
+
+    The hash of the ref if the same as the hash of the referenced object:
+
+    >>> hash(ref) == hash(ob)
+    True
+
+    Two refs to the same object are equal:
+
+    >>> WeakRef(ob) == ref
+    True
+
+    >>> ob2 = ZODB.tests.MinPO.MinPO(1)
+    >>> WeakRef(ob2) == ref
+    False
+
+    Lets save the reference and the referenced object in a database:
+
+    >>> db = ZODB.tests.util.DB()
+
+    >>> conn1 = db.open()
+    >>> conn1.root()['ob'] = ob
+    >>> conn1.root()['ref'] = ref
+    >>> transaction.commit()
+
+    If we open a new connection, we can use the reference:
+
+    >>> conn2 = db.open()
+    >>> conn2.root()['ref']() is conn2.root()['ob']
+    True
+    >>> hash(conn2.root()['ref']) == hash(conn2.root()['ob'])
+    True
+
+    But if we delete the referenced object and pack:
+
+    >>> del conn2.root()['ob']
+    >>> transaction.commit()
+    >>> ZODB.tests.util.pack(db)
+
+    And then look in a new connection:
+
+    >>> conn3 = db.open()
+    >>> conn3.root()['ob']
+    Traceback (most recent call last):
+    ...
+    KeyError: 'ob'
+
+    Trying to dereference the reference returns None:
+
+    >>> conn3.root()['ref']()
+
+    Trying to get a hash, raises a type error:
+
+    >>> hash(conn3.root()['ref'])
+    Traceback (most recent call last):
+    ...
+    TypeError: Weakly-referenced object has gone away
+
+    Always explicitly close databases: :)
+
+    >>> db.close()
+    >>> del ob, ref, db, conn1, conn2, conn3
+
+    When multiple databases are in use, a weakref in one database may
+    point to an object in a different database.  Let's create two new
+    databases to demonstrate this.
+
+    >>> dbA = ZODB.tests.util.DB(
+    ...     database_name = 'dbA',
+    ...     )
+    >>> dbB = ZODB.tests.util.DB(
+    ...     database_name = 'dbB',
+    ...     databases = dbA.databases,
+    ...     )
+    >>> connA1 = dbA.open()
+    >>> connB1 = connA1.get_connection('dbB')
+
+    Now create and add a new object and a weak reference, and add them
+    to different databases.
+
+    >>> ob = ZODB.tests.MinPO.MinPO()
+    >>> ref = WeakRef(ob)
+    >>> connA1.root()['ob'] = ob
+    >>> connA1.add(ob)
+    >>> connB1.root()['ref'] = ref
+    >>> transaction.commit()
+
+    After a succesful commit, the reference should know the oid,
+    database name and connection of the object.
+
+    >>> ref.oid == ob._p_oid
+    True
+    >>> ref.database_name == 'dbA'
+    True
+    >>> ref.dm is ob._p_jar is connA1
+    True
+
+    If we open new connections, we should be able to use the reference.
+
+    >>> connA2 = dbA.open()
+    >>> connB2 = connA2.get_connection('dbB')
+    >>> ref2 = connB2.root()['ref']
+    >>> ob2 = connA2.root()['ob']
+    >>> ref2() is ob2
+    True
+    >>> ref2.oid == ob2._p_oid
+    True
+    >>> ref2.database_name == 'dbA'
+    True
+    >>> ref2.dm is ob2._p_jar is connA2
+    True
+
+    Always explicitly close databases: :)
+
+    >>> dbA.close()
+    >>> dbB.close()
+
+    """
+
+
+def test_PersistentWeakKeyDictionary():
+    """Persistent weak key dictionary
+
+    This is akin to WeakKeyDictionaries. Note, however, that removal
+    of items is extremely lazy. See below.
+
+    We'll start by creating a PersistentWeakKeyDictionary and adding
+    some persistent objects to it.
+
+    >>> from persistent.wref import PersistentWeakKeyDictionary
+    >>> d = PersistentWeakKeyDictionary()
+    >>> import ZODB.tests.util
+    >>> p1 = ZODB.tests.util.P('p1')
+    >>> p2 = ZODB.tests.util.P('p2')
+    >>> p3 = ZODB.tests.util.P('p3')
+    >>> d[p1] = 1
+    >>> d[p2] = 2
+    >>> d[p3] = 3
+
+    We'll create an extra persistent object that's not in the dict:
+
+    >>> p4 = ZODB.tests.util.P('p4')
+
+    Now we'll excercise iteration and item access:
+
+    >>> l = [(str(k), d[k], d.get(k)) for k in d]
+    >>> l.sort()
+    >>> l
+    [('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
+
+    And the containment operator:
+
+    >>> [p in d for p in [p1, p2, p3, p4]]
+    [True, True, True, False]
+
+    We can add the dict and the referenced objects to a database:
+
+    >>> db = ZODB.tests.util.DB()
+
+    >>> conn1 = db.open()
+    >>> conn1.root()['p1'] = p1
+    >>> conn1.root()['d'] = d
+    >>> conn1.root()['p2'] = p2
+    >>> conn1.root()['p3'] = p3
+    >>> transaction.commit()
+
+    And things still work, as before:
+
+    >>> l = [(str(k), d[k], d.get(k)) for k in d]
+    >>> l.sort()
+    >>> l
+    [('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
+    >>> [p in d for p in [p1, p2, p3, p4]]
+    [True, True, True, False]
+
+    Likewise, we can read the objects from another connection and
+    things still work.
+
+    >>> conn2 = db.open()
+    >>> d = conn2.root()['d']
+    >>> p1 = conn2.root()['p1']
+    >>> p2 = conn2.root()['p2']
+    >>> p3 = conn2.root()['p3']
+    >>> l = [(str(k), d[k], d.get(k)) for k in d]
+    >>> l.sort()
+    >>> l
+    [('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
+    >>> [p in d for p in [p1, p2, p3, p4]]
+    [True, True, True, False]
+
+    Now, we'll delete one of the objects from the database, but *not*
+    from the dictionary:
+
+    >>> del conn2.root()['p2']
+    >>> transaction.commit()
+
+    And pack the database, so that the no-longer referenced p2 is
+    actually removed from the database.
+
+    >>> ZODB.tests.util.pack(db)
+
+    Now if we access the dictionary in a new connection, it no longer
+    has p2:
+
+    >>> conn3 = db.open()
+    >>> d = conn3.root()['d']
+    >>> l = [(str(k), d[k], d.get(k)) for k in d]
+    >>> l.sort()
+    >>> l
+    [('P(p1)', 1, 1), ('P(p3)', 3, 3)]
+
+    It's worth nothing that that the versions of the dictionary in
+    conn1 and conn2 still have p2, because p2 is still in the caches
+    for those connections.
+
+    Always explicitly close databases: :)
+
+    >>> db.close()
+
+    """
+
+def test_suite():
+    from doctest import DocTestSuite
+    return DocTestSuite()