New Feature:

  The filestorage packer configuration option noe accepts calues of
  the form ``modname:expression``, allowing the use of packer
  factories with options.

src/CHANGES.txt

@@ -41,6 +41,10 @@ New Features
   index file if an output file name is given via the --output/-o
   option.
 
+- The filestorage packer configuration option noe accepts calues of
+  the form ``modname:expression``, allowing the use of packer
+  factories with options.
+
 Bugs Fixed
 ----------
 

src/ZODB/FileStorage/zconfig.txt

@@ -134,6 +134,33 @@ packer
 
     >>> fs.close()
 
+    If the packer contains a ':', then the text after the first ':' is
+    interpreted as an expression. This is handy to pass limited
+    configuration information to the packer:
+
+    >>> def packer_factory(name):
+    ...     def packer(storage, referencesf, stop, gc):
+    ...         print repr(name), referencesf, storage is fs, gc,
+    ...         print storage.pack_keep_old
+    ...     return packer
+    >>> ZODB.FileStorage.config_demo_printing_packer_factory = packer_factory
+
+    >>> fs = ZODB.config.storageFromString("""
+    ... <filestorage>
+    ...     path my.fs
+    ...     packer ZODB.FileStorage:config_demo_printing_packer_factory('bob ')
+    ... </filestorage>
+    ... """)
+
+    >>> import time
+    >>> db = ZODB.DB(fs) # writes object 0
+    >>> fs.pack(time.time(), 42)
+    'bob ' 42 True True True
+
+    >>> fs.close()
+
+
+
 pack-gc
     If false, then no garbage collection will be performed when
     packing.  This can make packing go much faster and can avoid

src/ZODB/component.xml

@@ -44,7 +44,7 @@
         raised.
       </description>
     </key>
-    <key name="packer" datatype="dotted-name">
+    <key name="packer" datatype="string">
       <description>
         The dotted name (dotted module name and object name) of a
         packer object.  This is used to provide an alternative pack

src/ZODB/config.py

@@ -158,8 +158,15 @@ class FileStorage(BaseConfig):
         config = self.config
         options = {}
         if getattr(config, 'packer', None):
-            m, name = config.packer.rsplit('.', 1)
-            options['packer'] = getattr(__import__(m, {}, {}, ['*']), name)
+            packer = config.packer
+            if ':' in packer:
+                m, expr = packer.split(':', 1)
+                m = __import__(m, {}, {}, ['*'])
+                options['packer'] = eval(expr, m.__dict__)
+            else:
+                m, name = config.packer.rsplit('.', 1)
+                m = __import__(m, {}, {}, ['*'])
+                options['packer'] = getattr(m, name)
 
         for name in ('blob_dir', 'create', 'read_only', 'quota', 'pack_gc',
                      'pack_keep_old'):