id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
10354	encoding.force_unicode exception unclear/vague, update to clarify exception	monkut	nobody	"I just spent over an hour tracking down a bug in my code.

It was a very simple beginner mistake.
I forgot to return a value in a model's unicode method.



{{{
class MyModel(models.Model):
    name = models.CharField()

    def __unicode__(self):
        self.name[:25]   
}}}

Unfortunatly this isn't caught a propagated in a clear way and results in the following exception, when accessing the admin applicaiton.


{{{
TypeError at /admin/specmaker/project/add/
coercing to Unicode: need string or buffer, NoneType foundRequest Method:	POST
Request URL:	http://127.0.0.1:8000/admin/specmaker/project/add/
Exception Type:	TypeError
Exception Value:	coercing to Unicode: need string or buffer, NoneType found
Exception Location:	C:\Python26\Lib\site-packages\django\utils\encoding.py in force_unicode, line 49
Python Executable:	C:\Python26\python.exe
Python Version:	2.6.0
Python Path:	['D:\\PROGRAMMING\\Workspace\\GEODJANGO-TUTORIAL\\geodjango\\specmgr', 'C:\\Python26\\lib\\site-packages\\setuptools-0.6c9-py2.6.egg', 'C:\\Python26\\lib\\site-packages\\sphinx-0.4.3-py2.6.egg', 'C:\\Python26\\lib\\site-packages\\docutils-0.5-py2.6.egg', 'C:\\Python26\\lib\\site-packages\\jinja-1.2-py2.6-win32.egg', 'C:\\Python26\\lib\\site-packages\\pygments-0.11.1-py2.6.egg', 'C:\\Python26\\python26.zip', 'C:\\Python26\\DLLs', 'C:\\Python26\\lib', 'C:\\Python26\\lib\\plat-win', 'C:\\Python26\\lib\\lib-tk', 'C:\\Python26', 'C:\\Python26\\lib\\site-packages', 'C:\\Python26\\lib\\site-packages\\PIL', 'C:\\Python26\\lib\\site-packages\\win32', 'C:\\Python26\\lib\\site-packages\\win32\\lib', 'C:\\Python26\\lib\\site-packages\\Pythonwin']
Server time:	Wed, 25 Feb 2009 17:58:37 +0900
}}}


I'm sure regular users of django may no what causes this right-away, but beginners like myself may be stuck trying to debug django code trying to find what this exception is.

I propose something like this (encoding.force_unicode) to clarify this exception:


{{{
def force_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
    """"""
    Similar to smart_unicode, except that lazy instances are resolved to
    strings, rather than kept as lazy objects.

    If strings_only is True, don't convert (some) non-string-like objects.
    """"""
    if strings_only and isinstance(s, (types.NoneType, int, long, datetime.datetime, datetime.date, datetime.time, float)):
        return s
    try:
        if not isinstance(s, basestring,):
            if hasattr(s, '__unicode__'):
                try:
                    s = unicode(s)
                except TypeError:
                    msg = u""%s's __unicode__ method not returning proper unicode string"" % (repr(type(s)))
                    raise TypeError(msg)
}}}

So the error will display as:


{{{
TypeError at /admin/specmaker/project/add/
<class 'specmgr.specmaker.models.Project'>'s __unicode__ method not returning proper unicode stringRequest Method:	POST
Request URL:	http://127.0.0.1:8000/admin/specmaker/project/add/
Exception Type:	TypeError
Exception Value:	<class 'specmgr.specmaker.models.Project'>'s __unicode__ method not returning proper unicode string
Exception Location:	C:\Python26\lib\site-packages\django\utils\encoding.py in force_unicode, line 53
Python Executable:	C:\Python26\python.exe
Python Version:	2.6.0
Python Path:	['D:\\PROGRAMMING\\Workspace\\GEODJANGO-TUTORIAL\\geodjango\\specmgr', 'C:\\Python26\\lib\\site-packages\\setuptools-0.6c9-py2.6.egg', 'C:\\Python26\\lib\\site-packages\\sphinx-0.4.3-py2.6.egg', 'C:\\Python26\\lib\\site-packages\\docutils-0.5-py2.6.egg', 'C:\\Python26\\lib\\site-packages\\jinja-1.2-py2.6-win32.egg', 'C:\\Python26\\lib\\site-packages\\pygments-0.11.1-py2.6.egg', 'C:\\Python26\\python26.zip', 'C:\\Python26\\DLLs', 'C:\\Python26\\lib', 'C:\\Python26\\lib\\plat-win', 'C:\\Python26\\lib\\lib-tk', 'C:\\Python26', 'C:\\Python26\\lib\\site-packages', 'C:\\Python26\\lib\\site-packages\\PIL', 'C:\\Python26\\lib\\site-packages\\win32', 'C:\\Python26\\lib\\site-packages\\win32\\lib', 'C:\\Python26\\lib\\site-packages\\Pythonwin']
Server time:	Wed, 25 Feb 2009 18:21:57 +0900
}}}



  "		closed	Core (Other)	1.0		wontfix	exception-clarification		Unreviewed	1	0	0	0	0	0