Merged r40536 from 2.9 branch:

ObjectManager now has an hasObject method to test presence. This
brings it in line with BTreeFolder.

doc/CHANGES.txt

@@ -26,6 +26,9 @@ Zope Changes
 
     Features added
 
+      - ObjectManager now has an hasObject method to test presence. This
+        brings it in line with BTreeFolder.
+
       - Using FastCGI is offically deprecated.
 
       - Improved logging of ConflictErrors. All conflict errors are

lib/python/OFS/ObjectManager.py

@@ -272,6 +272,20 @@ class ObjectManager(
             raise AttributeError, id
         return default
 
+    def hasObject(self, id):
+        """Indicate whether the folder has an item by ID.
+
+        This doesn't try to be more intelligent than _getOb, and doesn't
+        consult _objects (for performance reasons). The common use case
+        is to check that an object does *not* exist.
+        """
+        if (id in ('.', '..') or
+            id.startswith('_') or
+            id.startswith('aq_') or
+            id.endswith('__')):
+            return False
+        return getattr(aq_base(self), id, None) is not None
+
     def _setObject(self, id, object, roles=None, user=None, set_owner=1,
                    suppress_events=False):
         """Set an object into this container.

lib/python/OFS/interfaces.py

@@ -531,6 +531,10 @@ class IObjectManager(IZopeObject, ICopyContainer, INavigation, IManageable,
         """
         """
 
+    def hasObject(id):
+        """Indicate whether the folder has an item by ID.
+        """
+
     def objectIds(spec=None):
         """List the IDs of the subobjects of the current object.
 

lib/python/OFS/tests/testObjectManager.py

@@ -328,6 +328,22 @@ class ObjectManagerTests(PlacelessSetup, unittest.TestCase):
         om2._setObject(ob.getId(), ob)
         self.assertRaises(DeleteFailed, om1._delObject, 'om2')
 
+    def test_hasObject(self):
+        om = self._makeOne()
+        self.failIf(om.hasObject('_properties'))
+        self.failIf(om.hasObject('_getOb'))
+        self.failIf(om.hasObject('__of__'))
+        self.failIf(om.hasObject('.'))
+        self.failIf(om.hasObject('..'))
+        self.failIf(om.hasObject('aq_base'))
+        om.zap__ = True
+        self.failIf(om.hasObject('zap__'))
+        self.failIf(om.hasObject('foo'))
+        si = SimpleItem('foo')
+        om._setObject('foo', si)
+        self.assert_(om.hasObject('foo'))
+        om._delObject('foo')
+        self.failIf(om.hasObject('foo'))
 
     def test_setObject_checkId_ok(self):
         om = self._makeOne()