collectstatic post-processing fails for references inside comments

[shreyas@…]

"python manage.py collectstatic" is attempting to parse references inside css comments and generating errors during post-processing. I am using:
STATICFILES_STORAGE = 'django.contrib.staticfiles.storage.CachedStaticFilesStorage'

eg.
The following snippet of code in test.css:

.gfg-collapse-closed {
  /* background-image : url('arrow_close.gif'); */
}

produces the following error:

ValueError: The file 'stylesheets/arrow_close.gif' could not be found with <django.contrib.staticfiles.storage.CachedStaticFilesStorage object at 0x1078a3910>.
collectstatic

Ideally, collectstatic should respect CSS comments and should not attempt to parse/reference files in lines that are commented out.

If the fix is too complex, a simple workaround might be to include a --ignore-error flag that would allow the application to continue post-processing even when it sees errors

[Kevin Christopher Henry]

CachedFilesMixin is using simple ​regular expressions to match url and @import statements, and so is picking up the ones inside comments. It would also have a problem if the text was inside a string.

If it's possible to rewrite the regex to cover all the corner cases, that would be the easy fix. But I doubt it. The robust way would be to parse the css files properly, but that would mean rewriting a lot of code...

[anonymous]

Could you recommend a path forward? Can we at least have it skip failed imports with a warning rather than break?

-Shreyas

[Pablo SEMINARIO]

I'm agree with the comment of @marfire, the correct way to do this is with a CSS parser, because there are many cases to be treated (multi-line comments, nested comments, broken comments, etc.)

Adding an option to skip failed imports was reported in ticket:19650 and it was marked as a duplicated of ticket:18958.

If you really need ignore these errors, you can create a subclass of CachedFilesMixin on your own project and add a try...except statement to handle these kind of exceptions.

[German Larrain]

This bit me today. "Dumb" workaround: replace that url in your comments with u r l.

[Ben Spaulding]

Just as an additional datapoint and another thing to consider if it comes to parsing the CSS, I recently started working on a project where the designers used some CSS expressions for an IE-specific stylesheet. The JScript used in one expression puts a particularly crazy bit like .replace('url("','').replace('")',''). As marfire said, that url bit in a string raises an exception. Fortunately I can overcome this for my project with a simple sublcass to make a very small change to the regular expression used. But that is one other thing to consider if it is decided that the CachedStaticFilesStorage needs to be more robust.