#12787: TemplateDoesNotExist exception does not report the correct template_name
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Reporter: trigeek38 | Owner: anonymous
Status: assigned | Milestone: 1.2
Component: Template system | Version: SVN
Resolution: | Keywords: TemplateDoesNotExist
Stage: Accepted | Has_patch: 1
Needs_docs: 0 | Needs_tests: 1
Needs_better_patch: 0 |
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Changes (by kmtracey):
* needs_docs: 1 => 0
* needs_tests: 0 => 1
Comment:
jkatzer: In the future please attach a single diff file created by svn
diff from the root of the tree. See:
http://docs.djangoproject.com/en/dev/internals/contributing/#patch-style.
That's much easier to deal with than a bunch of individual .diff files
zipped up.
I'm uncomfortable with the originally proposed way of fixing this, so I've
attached an alternative approach. The root cause of this bug is similar to
#12992. During `load_template`, the load of the requested template may
succeed but then `get_template_from_string` may raise
!TemplateDoesNotExist if the loaded template can't be compiled due to some
other template not existing. That !TemplateDoesNotExist, raised by
`load_template`, is interpreted by its caller to mean that the requested
template doesn't exist, leading to an erroneous report of the actual
problem on the debug page.
Attached patch changes the loader to code to fall back to returning the
template source and name, as it used to, if it was able to find the
requested template but attempting to compile it raises a
!TemplateSyntaxError. Thus the loader will only raise !TemplateSyntaxError
if the specifically-requested template does not exist. That prevents this
code:
{{{
#!python
for loader in template_source_loaders:
try:
source, display_name = loader(name, dirs)
return (source, make_origin(display_name, loader, name, dirs))
except TemplateDoesNotExist:
pass
raise TemplateDoesNotExist(name)
}}}
from moving on and trying other loaders, then ultimately ending with
`TemplateDoesNotExist(name)`, which mis-identifies the template that does
not exist.
That change alone is not sufficient to fix the problem, though. The
extends node `get_parent` method catches !TemplateDoesNotExist and turns
it into a !TemplateSyntaxError stating that the template specified to be
extended does not exist. Prior to r11862, the call covered by the
try/except was a `find_template_source` call, which would only raise
!TemplateDoesNotExist if that specific template does not exist. In r11862
the call inside the try/except was changed to `get_template`, which both
finds the source and compiles it, and so may raise !TemplateDoesNotExist
if some other template needed to compile the extended template does not
exist. We could either put the code here back the way it was before r11862
or remove this try/except entirely. The attached patch does the latter,
because I don't really see what additional value is added by the different
message ("... can't be extended because it doesn't exist") over a plain
template does not exist message.
There is a test in the patch, but it's not really sufficient since it does
not test both the base loader case and the cached loader case. But it does
illustrate when the problem arises.
--
Ticket URL: <http://code.djangoproject.com/ticket/12787#comment:6>
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