Staticfiles template tag does not fail silently

[Bouke Haarsma]

Last night we had a major outage on our site, due to a missing static file. We used {% static 'css/fancybox.jquery.css' %} in our base template, but that file had gone missing. As there were some caches involved, the problem presented only a few hours later when the caches expired. From what I understand is that template tags should fail silently as per the docs:

render() should never raise TemplateSyntaxError or any other exception. It should fail silently, just as template filters should.

So I was surprised that instead of failing silently, the template tag raised an exception (and brought the whole site to a stop). I think the template tag should fail silently instead of raising the exception.

 File "app/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 136, in get_response
   response = response.render()

 File "app/local/lib/python2.7/site-packages/django/template/response.py", line 104, in render
   self._set_content(self.rendered_content)

 File "app/local/lib/python2.7/site-packages/django/template/response.py", line 81, in rendered_content
   content = template.render(context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 140, in render
   return self._render(context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 134, in _render
   return self.nodelist.render(context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 823, in render
   bit = self.render_node(node, context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 837, in render_node
   return node.render(context)

 File "app/local/lib/python2.7/site-packages/django/template/loader_tags.py", line 123, in render
   return compiled_parent._render(context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 134, in _render
   return self.nodelist.render(context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 823, in render
   bit = self.render_node(node, context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 837, in render_node
   return node.render(context)

 File "app/local/lib/python2.7/site-packages/django/template/base.py", line 1107, in render
   return func(*resolved_args, **resolved_kwargs)

 File "app/local/lib/python2.7/site-packages/django/contrib/staticfiles/templatetags/staticfiles.py", line 13, in static
   return staticfiles_storage.url(path)

 File "app/config/storages.py", line 40, in url
   url = super(StaticStorage, self).url(name, force)

 File "app/local/lib/python2.7/site-packages/django/contrib/staticfiles/storage.py", line 114, in url
   hashed_name = self.hashed_name(clean_name).replace('\\', '/')

 File "app/local/lib/python2.7/site-packages/django/contrib/staticfiles/storage.py", line 74, in hashed_name
   (clean_name, self))

ValueError: The file 'styles/jquery.fancybox.css' could not be found with <config.storages.StaticStorage object at 0x36fee90>.

[Moritz Sichert]

Added patch (​Github Pull Request)

[Jannis Leidel]

First of all, please don't accept your own tickets, we have a community of ticket triagers that didn't have a chance to see this ticket since you didn't leave it at the Unreviewed state.

Secondly, I'm sorry but this isn't Django's fault, if you're missing a file, it's good to raise an exception. You quoted a part of the documentation of how to write the render method of custom template tags, not how template tags should work in general. It is an error to refer to a file with the staticfiles' static template tag as it uses a storage backend to calculate the URL of the static files. If you just want to generate a URL that is concatenated with STATIC_URL, use the core static template tag: ​https://docs.djangoproject.com/en/dev/ref/templates/builtins/?from=olddocs#std:templatetag-static

[anon0405@…]

It would be nice if there were a setting that toggled whether this fails loudly or silently -- often it is better to serve an html file with broken formatting (missing css), missing functionality (missing js), or missing niceties (missing .ico) than to throw up a server error and prevent any information from reaching the end user.

Especially where the behavior of {% static %} is explicitly to not raise errors in development, the current behavior creates time bombs that are out of step with the rest of django's template error philosophy -- fail silently whenever possible.

Two options are:

• {% static 'file/path.stuff' True %} -- passing an optional parameter of whether to fail silently, so this can be turned on/off as needed
• STATIC_TAG_FAILS_SILENTLY=True -- an option in settings.py

If there isn't a way to make it fail silently in production, then the errors should somehow be raised in DEV so they are caught and fixed.