ToolbarMiddleware interferes with WhiteNoise Cache-Control header

[bhrutledge]

Summary

I'm switching an app from hosting static files on S3 to serving them from Django via WhiteNoise, behind the CloudFront CDN. WhiteNoise uses a middleware to intercept requests to STATIC_URL, and returns a file response. This is all relatively straightforward to set up.

Expected behaviour

• Hashed static files served via WhiteNoise should have a far-future Cache-Control header
• More broadly, Django CMS shouldn't set a "never cache" header for responses that don't include a toolbar

Actual behaviour

During testing I discovered that the Cache-Control header was still being set to "never cache" for static files. A dive through PDB led me to the ToolbarMiddleware and the behavior of using the cache-disabled EmptyToolbar while processing the response for non-CMS pages.

One possible workaround is to set CMS_TOOLBAR_HIDE = True, which short-circuits ToolbarMiddleware processing. However, this causes problems for us because we have views that have toolbar-related functionality, but aren't CMS pages. As a workaround for that, I subclassed ToolbarMiddleware to override is_cms_request to recognize the additional views.

Environment

• Python version: 2.7.15
• Django version: 1.11.18
• django CMS version: 3.4.5