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
12992	New template loaders lose debug information	Karen Tracey	nobody	"For a !TemplateSyntaxErorr, if you have the new-style template loaders in `settings.py`:

{{{
#!python
TEMPLATE_LOADERS = (
    'django.template.loaders.filesystem.Loader',
    'django.template.loaders.app_directories.Loader',
#     'django.template.loaders.eggs.Loader',
)
}}}

The `Template error` section of the debug page doesn't report the name of the template file where the problem occurred. Instead it reports `In template &lt;unknown source&gt;, error at line <whatever>`. One problem is the angle brackets aren't displayed properly but the real problem is that the source file name is ""unknown"".

Problem is due to the new-style loader's returning already-compiled templates (from http://code.djangoproject.com/browser/django/trunk/django/template/loader.py#L36):

{{{
#!python
    def __call__(self, template_name, template_dirs=None):
        return self.load_template(template_name, template_dirs)

    def load_template(self, template_name, template_dirs=None):
        source, origin = self.load_template_source(template_name, template_dirs)
        template = get_template_from_string(source, name=template_name)
        return template, origin
}}}

The old loaders return the `source, origin` as originally returned by `load_template_source`, and the template source is compiled into a `<django.template.Template>` when `get_template` finds what it got doesn't have a `render` (from http://code.djangoproject.com/browser/django/trunk/django/template/loader.py#L139):

{{{
#!python
def get_template(template_name):
    """"""
    Returns a compiled Template object for the given template name,
    handling template inheritance recursively.
    """"""
    template, origin = find_template(template_name)
    if not hasattr(template, 'render'):
        # template needs to be compiled
        template = get_template_from_string(template, origin, template_name)
    return template
}}}

That call to `get_template_from_string` includes the origin, which is what is needed to report the file name on the debug page.

Note `origin` in this bit of code is different from the `origin` returned by `load_template_source` above. That part of the `load_template_source` return value is called `display_name` in other parts of the code and is one of four args passed to `make_origin` to produce the `origin` passed in to `get_template_from_string` in the working path. So we cannot simply change the new-style loader code to pass the thing it calls `origin` to `get_template_from_string`. Nor does attempting to call `make_origin` with likely-seeming args in the new-style loader code work, possibly because I don't really have a clue what those args are supposed to all be. What does work is:

{{{
#!python
    def __call__(self, template_name, template_dirs=None):
        return self.load_template_source(template_name, template_dirs)
}}}

But I gather based on the doc here: http://docs.djangoproject.com/en/dev/ref/templates/api/#using-an-alternative-template-language that loaders are supposed to have a `load_template` method that returns a pre-compiled template so it would probably be better for someone with a clue in this area to figure out how to get the origin information properly attached to the already-compiled template returned by the new-style loaders.


"		closed	Template system	dev		fixed			Accepted	0	0	0	0	0	0