(While not directly related to Quixote, I hope this is
of interest to some list readers)

I ran into a bug involving persistent ZODB variables
and SimpleTAL 3.7 and thought I should pass along a
description (and a solution).

The long and the short of it is that the python
function callable returns true for *all* ZODB
persistent variables.

This means trying to do things like
someone@somewhere.com
will fail if user is a persistent variable.

There is a thread about callable and persistent
variables here:

http://mail.zope.org/pipermail/zodb-dev/2003-October/006076.html

The suggested replacement for callable (when placed in
simpleTALES.py) seems to do the trick.  Here it is:

def callable(thing):
    import ExtensionClass, __builtin__
    if hasattr(thing, '__basicnew__'):
        # __basicnew__ is a sign of ExtensionClass;
nothing in the
        # Python core, or any other known extension
module, has it.
        return (isinstance(thing,
ExtensionClass.ExtensionClass) or
                hasattr(thing, "__call__"))
    else:
        # Under the theory that only ExtensionClass
sets tp_call
        # even when instances aren't intended to be
callable.
        return __builtin__.callable(thing)


Below is an example trace of the error:

File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTAL.py",
line 608, in expand
    self.expandInline (context, encodingFile,
interpreter)
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTAL.py",
line 536, in expandInline
    ourInterpreter.execute (self)
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTAL.py",
line 199, in execute
    self.commandHandler[cmnd[0]] (cmnd[0], cmnd[1])
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTAL.py",
line 287, in cmdContent
    result = self.context.evaluate (args[2],
self.originalAttributes)
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTALES.py",
line 388, in evaluate
    return self.evaluatePath (expr)
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTALES.py",
line 430, in evaluatePath
    return self.traversePath (allPaths[0])
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTALES.py",
line 577, in traversePath
    temp = val.value((index,pathList))
  File
"/home/dpotter/localpy/rssdemo/ui/gotham/simpletal/simpleTALES.py",
line 99, in value
    return apply (self.ourValue, ())
AttributeError: __call__

Regards,
Dan