The final INTERNAL_IPS fix for development hosts

Django’s INTERNAL_IPS setting is an ongoing source of frustration and confusion (not only, but also) for users of django-debug-toolbar, especially when using non-local addresses. This is very useful for testing a website using mobile devices if you do not have a very fast internet connection where it does not matter whether you connect to a host through the local network or via the internet, for example using localtunnel.

For some time we had a utility function which automatically added all detected network interface IPs to INTERNAL_IPS. However, this does not work when using virtualization software such as Docker or Vagrant with port forwarding, because the VM’s (or container’s) IP isn’t what you want – you want the host IP.

Once I took a step back I saw a different, but much simpler solution. INTERNAL_IPS can be replaced with an object which simply answers True to all __contains__-type questions:

if DEBUG:
    # `debug` is only True in templates if the vistor IP is in INTERNAL_IPS.
    INTERNAL_IPS = type(str('c'), (), {'__contains__': lambda *a: True})()