I have defined some harnesses to group together a common set of signals between different schematic pages/hierarchy levels. Some of the pages are re-used in other designs, and in some of those designs one or more of the signals should be connected to ground. Doing so creates this error in schematic:
Global Power-Object GND has been reduced to local level by presence of port
and all of the grounds on that page are now disconnected, breaking the layout. I did find one documentation page about this error but all it says is "don't do that" without offering a way to make it work.
I temporarily worked around it by adding a net tie component - I made a 0603 footprint with a piece of copper between the pads.
The workaround schematic looks like this:
In this particular case this is OK to have a (dummy) component in the ground path, however in most cases the net that's part of the harness should have any component pins tie directly to the ground plane so this workaround isn't useful.
