Fix connection to wifi APs from user menu (RH #1628263)

In recent Fedora 29, connecting to wifi access points from the user menu (top-right menu) does not work. Clicking the 'Connect' button just animates it but does nothing else. The logs show an error "JS ERROR: Error: Expected type utf8 for Argument 'specific_object' but got type 'undefined'".

Looking into this, it seems the problem is these uses of the path property of an NMAccessPoint. NMAccessPoint inherits from NMObject, and NMObject does have a path property:

https://developer.gnome.org/libnm/stable/NMObject.html#NMObject--path

so at first glance this seems fine. But I poked around a bit using libnm via Python (which goes via introspection, just like this JS code does), and found that indeed AccessPoint objects don't seem to have a path property there either.

Looking at the libnm code, this actually makes sense, because the property is marked "(skip)":

https://github.com/NetworkManager/NetworkManager/blob/master/libnm/nm-object.c#L1291

and the introspection docs suggest that means it should be left out of introspected output:

https://wiki.gnome.org/Projects/GObjectIntrospection/Annotations#Symbol_visibility

I'm a bit concerned that this was only found recently - whereas the change to use .path in gnome-shell dates from October 2017 (d71af5e5) and the property has been marked (skip) in NM since at least 2016 - but this all seems to add up. The obvious fix is to replace use of .path with .get_path(), which returns the path and is not marked (skip) and so is available via introspection. I tested that this works in Python and also did a test build of gnome-shell with this change and installed it on an affected system, it does seem to fix the bug.

Signed-off-by: Adam Williamson awilliam@redhat.com