KeyError would be raised during ZODB serialization; catch that. Not sure if...

KeyError would be raised during ZODB serialization; catch that. Not sure if this is the best solution or not but it gets zope.container passing.

persistent/persistence.py

@@ -390,8 +390,16 @@ class Persistent(object):
         # detail, the '_cache' attribute of the jar.  We made it a
         # private API to avoid the cycle of keeping a reference to
         # the cache on the persistent object.
-        if self.__jar is not None and self.__oid is not None:
-            self.__jar._cache.mru(self.__oid)
+        if self.__jar is not None and self.__oid is not None and self._p_state >= 0:
+            # This scenario arises in ZODB: ZODB.serialize.ObjectWriter
+            # can assign a jar and an oid to newly seen persistent objects,
+            # but because they are newly created, they aren't in the
+            # pickle cache yet. There doesn't seem to be a way to distinguish
+            # that at this level, all we can do is catch it
+            try:
+                self.__jar._cache.mru(self.__oid)
+            except KeyError:
+                pass
 
 
 def _estimated_size_in_24_bits(value):

persistent/tests/test_persistence.py

@@ -1319,7 +1319,29 @@ class PyPersistentTests(unittest.TestCase, _Persistent_Base):
 
     def _clearMRU(self, jar):
         jar._cache._mru[:] = []
- 
+
+    def test_accessed_with_jar_and_oid_but_not_in_cache(self):
+        # This scenario arises in ZODB: ZODB.serialize.ObjectWriter
+        # can assign a jar and an oid to newly seen persistent objects,
+        # but because they are newly created, they aren't in the
+        # pickle cache yet.
+        # Nothing should blow up when this happens
+        from persistent._compat import _b
+        KEY = _b('123')
+        jar = self._makeJar()
+        c1 = self._makeOne()
+        c1._p_oid = KEY
+        c1._p_jar = jar
+        orig_mru = jar._cache.mru
+        def mru(oid):
+            # Mimic what the real cache does
+            if oid not in jar._cache._mru:
+                raise KeyError(oid)
+            orig_mru(oid)
+        jar._cache.mru = mru
+        c1._p_accessed()
+        self._checkMRU(jar, [])
+
 _add_to_suite = [PyPersistentTests]
 
 if not os.environ.get('PURE_PYTHON'):
@@ -1336,7 +1358,7 @@ if not os.environ.get('PURE_PYTHON'):
 
             def _checkMRU(self, jar, value):
                 pass # Figure this out later
-        
+
             def _clearMRU(self, jar):
                 pass # Figure this out later