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
3349	If an ImportError occurs within some loaders a rather confusing exception is raised.	Chris Wagner <cw264701@…>	nobody	"The problem is, when Django attempts to load a custom tag library (in source:django/trunk/django/template/__init__.py, in the {{{get_library()}}} function), it ''traps'' all {{{ImportError}}}'s, regardless of where they are ''thrown'' from:
{{{
try:
    mod = __import__(module_name, {}, {}, [''])
except ImportError, e:
    raise InvalidTemplateLibrary, ""Could not load template library from %s, %s"" % (module_name, e)
}}}

An example...

If I have a ""view"" like so:
{{{
def my_view(request):
    return render_to_response('my.tpl', {})
}}}

...And a corresponding template:
{{{
{% load tag_lib %}
<h1>my template</h1>
...
}}}

...Now, here's the tag library {{{tag_lib}}}:
{{{
import notthere
...
}}}

...Invoking our view, now, will yield a not-very-easy-to-understand (unless you already know the problem) error message:
{{{
TemplateSyntaxError at /my_view
'tag_lib' is not a valid tag library: Could not load template library from django.templatetags.tag_lib, No module named notthere
Request Method:     GET
Request URL:        http://localhost:8000/my_view
Exception Type:     TemplateSyntaxError
Exception Value:    'tag_lib' is not a valid tag library: Could not load template library from django.templatetags.tag_lib, No module named notthere
Exception Location: /usr/lib/python2.4/site-packages/Django-0.95-py2.4.egg/django/template/defaulttags.py in load, line 692
}}}
You may need to look closely to notice that the root of the problem was that our tag library tried to load a module {{{notthere}}}; the problem ''was not'' that we tried to load a non-existant tag library.

This is essentially the same message that you will get when trying to load a tag library that is completely non-existant - i.e., if our template were:
{{{
{% load not_tag_lib %}
<h1>my template</h1>
...
}}}

We would now see the error message:
{{{
TemplateSyntaxError at /my_view
'not_tag_lib' is not a valid tag library: Could not load template library from django.templatetags.not_tag_lib, No module named not_tag_lib
...
}}}

The type of error message that I would like to see would be one that is not obfuscated and wrapped in a {{{TemplateSyntaxError}}} exception.  Such a useful error message ''will'' be displayed if some other problem occurs in our tag library; for instance, if our tag library looks like
{{{
blablabla
...
}}}
then we will be greeted with the slightly-more-decipherable error message,
{{{
NameError at /my_view
name 'blablabla' is not defined
Request Method:     GET
Request URL:        http://localhost:8000/my_view
Exception Type:     NameError
Exception Value:    name 'blablabla' is not defined
Exception Location: /usr/lib/python2.4/site-packages/Django-0.95-py2.4.egg/django/template/__init__.py in get_library, line 880
}}}

I'm not certain that there's a way around this (I'm relatively new to Python), but I suspect it is possible to resolve by (somehow) determining which file/line the ImportError originated from/on, and adjusting the error message that is raised in the {{{get_library()}}} function.  I'd be willing to spend time on a patch if I you're all willing to accept one. :)"		closed	Template system	dev		fixed		me@… ramusus@… andrewbadr.etc@…	Accepted	1	0	1	0	0	0