[bug] CompressStaticFilesStorage: "malformed css" error on collectstatic

[pandafy]

Describe the bug
The openwisp_utils.storage.CompressStaticFilesStorage backend causes collectstatic to fail when used in environments with the latest version of drf-yasg. The static files compressor (csscompressor) triggers ValueError: malformed css.

Steps To Reproduce
Steps to reproduce the behavior:

1. Set up a Django project using drf-yasg and configure openwisp_utils.storage.CompressStaticFilesStorage as the staticfiles backend
2. Run collectstatic
3. See error: ValueError: malformed css

Expected behavior
collectstatic completes successfully, even with modern CSS from third-party packages such as drf-yasg.

[pandafy]

If anyone runs into this issue, downgrading to drf-yasg==1.21.11 fixes the issue with the collectstatic command. This can be used as a workaround until this issue is fixed.

[SAMurai-16]

hi @pandafy i would like to work on this one

[pandafy]

Sure @SAMurai-16, we need to understand the root the problem first.

[SAMurai-16]

I tried to reproduce the issue and found that drf-yasg==1.21.11 can be updated to 1.21.14 by excluding drf-yasg's CSS files from minification in CompressStaticFilesStorage. The newer drf-yasg versions include Swagger UI CSS that is incompatible with the csscompressor library.
The files are pre-minified by Swagger UI so excluding drf-yasg's CSS files from minification shouldn't be a problem.

[nemesifier]

The package we're using for minification and compression is unmaintained. I drafted an alternative here:
https://github.com/openwisp/django-minify-compress-staticfiles

Help in making it work, fix CI and add more tests is welcome, once it works we can publish it on Pypi and switch to it.

[nemesifier]

Once openwisp/django-minify-compress-staticfiles#7 is merged and released, we can replace what we're using now with this new package.

We may have to update ansible-openwisp2 and docker-openwisp, I am not 100% sure, maybe we won't but let's double check.