Some servers may not support current-user-principal

[tobixen]

I found a URL to some old test calendar that I hadn't been running tests towards for quite a while. It seems to be a sabre-variant (possibly baikal or a relative of baikal). None of the tests would pass. I looked a bit closer and found that the calendar server does not return any current principal. Reading the sabre documentation, I noticed that one needs to install an ACL module to get support for the current-user-principal property.

This is a big problem, since the documented and recommended way to use the library is "find the principal, then use that object to do other operations". It is possible to instantiate calendars without using the current-user-principal property if one knows the calendar-URLs.

It's needed to:

• Fix the test framework so that some tests will be run even on servers not supporting current-user-principal.
• Fix the code so that it breaks more or less gracefully if current-user-principal is not supported.
• Highlight this in the documentation
• Consider this issue when working on the 1.0 API.

None of this will make it into the v0.9-release.

[tobixen]

Revisited that server, seems like there is some kind of communication issue, it should definitively support current-user-principal. Raised an issue at sabre-io/dav#1426