Add some checks for the optional fields of ModifyForm

MoinMoin/items/__init__.py

 # Copyright: 2012 MoinMoin:CheerXiao
 # Copyright: 2009 MoinMoin:ThomasWaldmann
 # Copyright: 2009-2011 MoinMoin:ReimarBauer
 # Copyright: 2009 MoinMoin:ChristopherDenter
 # Copyright: 2008,2009 MoinMoin:BastianBlank
 # Copyright: 2010 MoinMoin:ValentinJaniaut
 # Copyright: 2010 MoinMoin:DiogenesAugusto
 # License: GNU GPL v2 (or any later version), see LICENSE.txt for details.
 
 """
@@ skipping 424 matching lines @@
             """
             Dump useful data out of :self. :item contains the old item and
             should not be the primary data source; but it can be useful in case
             the data in :self is not sufficient.
 
             :returns: a tuple (meta, data, contenttype_guessed, comment),
                       suitable as arguments of the same names to pass to
                       item.modify
             """
             meta = self['meta_form'].value.copy()
-            meta.update(item.meta_text_to_dict(self['extra_meta_text'].value))
+            if self['extra_meta_text']:  # it's an optional field
+                meta.update(item.meta_text_to_dict(self['extra_meta_text'].value))

[Thomas.J.Waldmann, 2013/07/23 15:18:59]

what happens without that check?

what values have are present in that case for:

self['extra_meta_text'].value
self['extra_meta_text']

[spy, 2013/07/24 21:11:43]

Without that check in case when the 'extra_meta_text' field wasn't set up (for
example when the 'extra_meta_text' wasn't sent with the POST request) it raises
an exception in item.meta_text_to_dict(self['extra_meta_text'].value). The value
is None and it is used in json deserialization.

This check is useful for the +addcomment view implementation, because there is
no 'extra_meta_text' form field to be sent to this view. We can reuse the
existing _dump method if we check the 'extra_meta_text' field was set up
correctly.


Here is the code snippet from flatland's scalars.py:

class Scalar(Element):
    ...
    def __nonzero__(self):
        return True if self.u and self.value else False
    ...

If the field was not set up:
self['extra_meta_text'].value is equal to None
self['extra_meta_text'] is equal to False

[Thomas.J.Waldmann, 2013/07/26 12:02:17]

ok.

             data, contenttype_guessed = self['content_form']._dump(item.content)
             comment = self['comment'].value
             return meta, data, contenttype_guessed, comment
 
     def do_modify(self):
         """
         Handle +modify requests, both GET and POST.
 
         This method should be overridden in subclasses, providing polymorphic
         behavior for the +modify view.
@@ skipping 365 matching lines @@
         # pointless for non-existing items
         pass
 
     def destroy(self, comment=u'', destroy_item=False):
         # pointless for non-existing items
         pass
 
 
 from ..util.pysupport import load_package_modules
 load_package_modules(__name__, __path__)