When building net-misc/networkmanager-1.2.4 the vapi files are generated. libnm-util.vapi is generated properly, but libnm-glib.vapi is empty (it only contains a comment which indicates it has been generated by vapigen-0.32. The build-log also shows that vapigen was run successful. I need this vapi file to build some vala application which uses networkmanager. As a workaround I now use the .vapi file from the libnm-glib-dev Ubuntu package.
Can you report this to upstream and post the link here please? Thanks bugzilla.gnome.org
Also this is indeed a problem, please note that upstream considers libnm-glib deprecated.
fixed in 1.4