[Zope-dev] zope.xmlpickle

[Jim Fulton]

Michael Dunstan wrote:
> Hi all,
> 
> I have been trying out ``zope.xmlpickle`` as a alternative to
> XMLExportImport in Zope2.

Cool. xmlpickle is really a newer version of the xml pickler used in
Zope 2's export/import.  It's main goal is to provide nicer pickles:

- More readable

- More diff friendly.  It does this my:

   - sorting dictionary items

   - eliminating unused memo references

It would be nice to integrate this back into the export/import
machinery.  Some care would be needed to make it compatible with
the old xml pickles.

 > Seems to do the job just fine. Grab Zope
> 2.9.3 and install zope.xmlpickle by hand using something of the form:
> 
>  % cd /opt/Zope-2.9/lib/python/zope
>  % svn checkout 
> svn://svn.zope.org/repos/main/Zope3/trunk/src/zope/xmlpickle
> 
> Then using zopectl debug:
> 
>  >>> from zope.xmlpickle import dumps
> 
> Picking on something simple to start with:
> 
>  >>> xml = dumps(app.acl_users.aq_base)
>  >>> print xml
>  <?xml version="1.0" encoding="utf-8" ?>
>  <pickle>
>    <initialized_object>
>      <klass>
>        <global name="__newobj__" module="copy_reg"/>
>      </klass>
>      <arguments>
>        <tuple>
>          <global name="SiteErrorLog"
> module="Products.SiteErrorLog.SiteErrorLog"/>
>        </tuple>
>      </arguments>
>      <state>
>        <dictionary>
>          <item key="_ignored_exceptions">
>              <tuple>
>                <string>Unauthorized</string>
>                <string>Redirect</string>
>                <string>NotFound</string>
>              </tuple>
>          </item>
>          <item key="copy_to_zlog">
>              <true/>
>          </item>
>          <item key="keep_entries">
>              <int>20</int>
>          </item>
>        </dictionary>
>      </state>
>    </initialized_object>
>  </pickle>
> 
> 
> That looks okay. But I strike problems with ``Missing.Value`` when
> trying this on something that includes a catalog. The simplest way
> to recreate the problem::
> 
>  >>> import Missing
>  >>> dumps(Missing.Value())
>  Traceback (most recent call last):
>    File "<stdin>", line 1, in ?
>    File "/opt/Zope-2.9/lib/python/zope/xmlpickle/xmlpickle.py", line
> 146, in dumps
>      p = _dumpsUsing_PicklerThatSortsDictItems(ob, 1)
>    File "/opt/Zope-2.9/lib/python/zope/xmlpickle/xmlpickle.py", line
> 73, in _dumpsUsing_PicklerThatSortsDictItems
>      _PicklerThatSortsDictItems(file, bin).dump(object)
>    File 
> "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py", 
> 
> line 231, in dump
>      self.save(obj)
>    File 
> "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py", 
> 
> line 324, in save
>      self.save_global(obj, rv)
>    File 
> "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py", 
> 
> line 753, in save_global
>      module = whichmodule(obj, name)
>    File 
> "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/pickle.py", 
> 
> line 825, in whichmodule
>      if func in classmap:
>  TypeError: unhashable type
> 
> Meanwhile, dumps seems to work quite happy with many other examples
> that I tried. Including all the content of a plone site minus a couple
> of the catalogs. And ``zope.xmlpickle.loads`` seems to do the right 
> thing too.
> 
> Any suggestions on getting a successful dumps of a Missing.Value?

You need someone with pickle zen to look at this.  I don't have time
right now myself.  If you don't find any other takers, then put an
issue in the Zope 3 collector.

Jim

-- 
Jim Fulton           mailto:jim at zope.com       Python Powered!
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