Neutron 'list' commands do not display 'fields' when there are no resources

[vishal yadav]

Neutron 'list commands' do not display 'fields' when there are no resources available.

neutron --version - 2.3.4
tenant - admin

Examples:
1) (Neutron) When there is no network:
[devbox@localhost devstack]$ neutron net-list

2) (Neutron) When there is no subnet:
[devbox@localhost devstack]$ neutron subnet-list

3) (Neutron) When there is no router:
[devbox@localhost devstack]$ neutron router-list

4) (Nova) When there is no instance:
[devbox@localhost devstack]$ nova list
+----+------+--------+------------+-------------+----------+
| ID | Name | Status | Task State | Power State | Networks |
+----+------+--------+------------+-------------+----------+
+----+------+--------+------------+-------------+----------+

5) (Cinder) When there is no volume:
[devbox@localhost devstack]$ cinder list
+----+--------+--------------+------+-------------+----------+-------------+
| ID | Status | Display Name | Size | Volume Type | Bootable | Attached to |
+----+--------+--------------+------+-------------+----------+-------------+
+----+--------+--------------+------+-------------+----------+-------------+

Neutron client should also display 'fields' when there are no resources:
1) To keep consistent behaviour with other OpenStack clients.
2) User should get the idea what information will be displayed about the resources even though there are no corresponding network resources.

[Sripriya (sseetha)]

Can you please confirm if this is a bug and change the status to 'Confirmed'?

[vishal yadav (vishalcdac07)]

It is a bug either with priority 'low' or 'wishlist.

[vishal yadav (vishalcdac07)]

While going through related issues, I found below bugs which are reason for this limitation (prettytable 0.6 and cliff dependencies)
- https://bugs.launchpad.net/python-neutronclient/+bug/1165962
- https://bugs.launchpad.net/python-neutronclient/+bug/1265926

Though above bugs were fixed to prevent gate failures, limitation to display empty lines for "list command" output in case of no resource still persists.

I am wondering if this limitation has been fixed in cliff (to behave similar to prettytable-0.7.2) to display formatted output in case of empty resource as specified in https://bugs.launchpad.net/python-neutronclient/+bug/1165962/comments/2

What about other python-*clients (nova, cinder, glance etc.) which are currently using prettytable>=0.6,<0.8? I am not sure if these clients are using cliff.

[Terry Howe (thowe-g)]

I disagree that headers should be displayed if there is no data. It could also cause variations on the headers that are displayed in the data/no data cases which would be confusing. Sometimes the headers are dependent on the data that is available like if there is a --long option.