ManifestStaticFilesStorage should also check in debug mode whether referenced file actually exists

[Fabian Köster]

We just had a case where we referenced a static file somewhere in the code like this

from django.templatetags.static import static
static("/path/to/a/file.png")

This worked perfectly fine on the development system and also on the staging systems. After deployment to the production system we noticed that it does not work when debug mode is disabled (debug = False) and the staticfiles are searched using the staticfiles.json manifest. In the code above we used an absolute path to the file whereas in the manifest all files are given with their relative path.

The following code can be used to reproduce the problem (using force=True is equivalent to debug=False in this case):

from django.contrib.staticfiles.storage import ManifestStaticFilesStorage
>>> ManifestStaticFilesStorage().url("path/to/a/file.png")
'/static/path/to/a/file.png'
>>> ManifestStaticFilesStorage().url("/path/to/a/file.png")
'/static/path/to/a/file.png'
>>> ManifestStaticFilesStorage().url("path/to/a/file.png", force=True)
'/static/path/to/a/file.f208556b8835.png'
>>> ManifestStaticFilesStorage().url("/path/to/a/file.png", force=True)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
    ManifestStaticFilesStorage().url('/path/to/a/file.png', force=True)
  File "/app/.pyenv/versions/3.7.2/lib/python3.7/site-packages/django/contrib/staticfiles/storage.py", line 153, in url
    return self._url(self.stored_name, name, force)
  File "/app/.pyenv/versions/3.7.2/lib/python3.7/site-packages/django/contrib/staticfiles/storage.py", line 132, in _url
    hashed_name = hashed_name_func(*args)
  File "/app/.pyenv/versions/3.7.2/lib/python3.7/site-packages/django/contrib/staticfiles/storage.py", line 420, in stored_name
    raise ValueError("Missing staticfiles manifest entry for '%s'" % clean_name)
ValueError: Missing staticfiles manifest entry for '/path/to/a/file.png'

I think the behaviour should be the same regardless if debug is True or False. I therefore propose to add a check to the debug = True code path that checks for the existance of the file as well so when referencing a non-existing file or giving an absolute path raises the same exception as it would on the production system with debug = False. I will create a PR for this in a few minutes.

[Fabian Köster]

Created a PR: ​https://github.com/django/django/pull/13587

[Carlton Gibson]

Hi Fabian. I think we have to save wontfix here - this is expected behaviour.

Passing an absolute path to static isn’t correct: all paths should be relative to STATIC_ROOT (​which is quite insistent that it ends in a `/`, so that relative paths can be appended). All the doc examples show using a relative path. Your examples using relative paths all work as expected so...

I think any change here would need to go via the DevelopersMailingList. Thanks.