[Eric] TypeError in DebugClientBase.py

[detlev]

Hello again,

On Sonntag, 22. November 2009, Seth Hill wrote:
> On Nov 22, 2009, at 3:33 AM, detlev wrote:
> > On Samstag, 21. November 2009, Seth Hill wrote:
> >> I'm working with a django 1.1 project, trying to get debugging going.
> >> I'm working with a form in a view function. I set a breakpoint in the
> >> view function, and get a TypeError in DebugClientBase.py:1608. It
> >> looks like the debugger is going through the locals and calling
> >> unicode() on all of them. Some of the locals in this case don't
> >> support the unicode method. When the debugger calls the unicode()
> >> method, it triggers an exception inside the running wsgi server. I
> >> get an error message on the web page, and the debug session stops
> >> working.
> >>
> >> My code looks like:
> >>
> >> forms.py:
> >> class NewCustomerForm(forms.Form):
> >>      name = forms.CharField()
> >>      # etc
> >>
> >> views.py:
> >> def create_customer(request):
> >>      if request.method == "POST":  # breakpoint here
> >>          form = NewCustomerForm(request.POST)
> >>          if form.is_valid():       # exception occurs when stepping
> >> to here
> >>
> >>
> >> The line in DebugClientBase.py looks like:
> >>      valtypestr = unicode(type(value))[1:-1]
> >
> > I don't understand, why type(value) does not support the unicode()
> > method.
> 
> Now that you mention it, I don't either. I've been digging a little
> deeper, and it seems that this is django's problem:
> 
> A django.forms.forms.Form class defines __metaclass__ =
> DeclarativeFieldsMetaclass (see source code http://
> code.djangoproject.com/browser/django/trunk/django/forms/forms.py:
> 336). I'm not entirely sure what it does, but I gather that it
> converts the class attributes into fields which can be accessed by a
> class instance.
> 
> Anyway, the metaclass seems to be promoting the __unicode__ function
> 
> of Form to type(Form):
>  >>> f = Form()
>  >>> type(f)
> 
> <class 'django.forms.forms.Form'>

That seems to be a Django bug because the net result is, that you cannot 
convert the result of type(f) to a unicode string.

> 
>  >>> unicode(type(f))
> 
> Traceback (most recent call last):
>     File "<console>", line 1, in <module>
> TypeError: unbound method __unicode__() must be called with Form
> instance as first argument (got nothing instead)
> 
>  >>> type(Form)
> 
> <class 'django.forms.forms.DeclarativeFieldsMetaclass'>
> 
>  >>> import inspect
>  >>> inspect.getsource(type(f).__unicode__)
> 
> '    def __unicode__(self):\n        return self.as_table()\n'
>

Can you please check, what ist returned by 
"inspect.getsource(type(f).__repr__)"?

What is needed by the eric4 debugger backend is a method to return the type of 
a variable as a string.
 
> 
> Anyway, the effect is still that if you are running the debugger and
> have a Form instance as a local variable, it will blow up. I would be
> willing to be that debugging a Model instance would have a similar
> effect (since it also uses a metaclass).
> 
> Maybe, instead of below a workaround should be:
> 
> if type(value) is type:
>      valtypestr = unicode(type(value))[1:-1]
> else:
>      valtypestr = repr(type(value))[1:-1]
> 
> However, even when doing that I suppose some metaclass could screw up
> __repr__ just like django's DeclarativeFieldsMetaclass did with
> __unicode__.  (?)
> 
> >> I've "fixed" the error by wrapping the line in a try:
> >>
> >> try:
> >>      valtypestr = unicode(type(value))[1:-1]
> >> except TypeError:
> >>      valtypestr = repr(type(value))[1:-1]
> >>

Regards
Detlev
-- 
Detlev Offenbach
detlev at die-offenbachs.de