[Eric] TypeError in DebugClientBase.py

[detlev]

On Dienstag, 24. November 2009, Seth Hill wrote:
> Hello,
> 
> I filed a bug report with the django folks too (
> http://code.djangoproject.com/ticket/12256). We determined that the issue
> isn't specific to django's use of metaclasses, but is in fact an issue with
> some older versions of python. This class:
> 
> class Foo(object):
>     def __init__(self, x):
>         self.x = x
>     def __unicode__(self):
>         print self.x
> 
> Generates the same TypeError when you call unicode(type(Foo())). My python
> is 2.5.1. I wasn't able to duplicate the issue on my Mac under python
>  2.6.2. I haven't been able to find a bug about this in the python bug list
>  though.

Over here it is working fine under openSUSE 11.2 with Python 2.6.2. 
Unfortunately I don't have a Python 2.5.x installation any more.

> 
> On Mon, Nov 23, 2009 at 9:16 AM, detlev <detlev at die-offenbachs.de> wrote:
> > 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__)"?
> >
> >>> inspect.getsource(type(f).__repr__)
> 
> Traceback (most recent call last):
>   File "<console>", line 1, in <module>
>   File "C:\Software\Python25\lib\inspect.py", line 629, in getsource
>     lines, lnum = getsourcelines(object)
>   File "C:\Software\Python25\lib\inspect.py", line 618, in getsourcelines
>     lines, lnum = findsource(object)
>   File "C:\Software\Python25\lib\inspect.py", line 461, in findsource
>     file = getsourcefile(object) or getfile(object)
>   File "C:\Software\Python25\lib\inspect.py", line 383, in getsourcefile
>     filename = getfile(object)
>   File "C:\Software\Python25\lib\inspect.py", line 363, in getfile
>     raise TypeError('arg is not a module, class, method, '
> TypeError: arg is not a module, class, method, function, traceback, frame,
> or code object
> 
> I assume this means that __repr__ hasn't been defined (not in source code
> anyway).
> 
> However, this also doesn't work even if I do define __repr__:
> >>> class Foo(Form):
> 
> ...    def __repr__(self):
> ...        return 'called repr'
> ...
> 
> >>> inspect.getsource(Foo().__repr___)
> 
> Traceback (most recent call last):
>   File "<console>", line 1, in <module>
>   File "C:\Software\Python25\lib\inspect.py", line 629, in getsource
>     lines, lnum = getsourcelines(object)
>   File "C:\Software\Python25\lib\inspect.py", line 618, in getsourcelines
>     lines, lnum = findsource(object)
>   File "C:\Software\Python25\lib\inspect.py", line 468, in findsource
>     raise IOError('could not get source code')
> IOError: could not get source code
> 
> >>> repr(Foo())
> 
> 'called repr'
> 
> But that might be because I'm doing it on the console.
> 
> > What is needed by the eric4 debugger backend is a method to return the
> > type of
> > a variable as a string.
> 
> This is kinda wacky, but might work:
> 
> t = type(value)
> if not t is type:
>     t = type(t)
> valtypestr = unicode(t)[1:-1]
> 
> If f = Foo(), and Foo defines a metaclass, then type(f) isn't <type
>  'type'>. However, type(type(f)) should be.
> 
> > > 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
> 


-- 
Detlev Offenbach
detlev at die-offenbachs.de