[IOS-XR] learn igmp fails to run

[geortich]

Description

pyats/genie learn igmp fails to run due to a twofold problem.

1. There's an issue with the igmp parser. I have logged a separate issue including a fix, in the genieparser repo.
2. The codebase assumes that there is at least one VRF enabled for IGMP and that VRF has at least one IGMP enabled interface.

Example

• Apply patch in 1. above to fix the first issue

• run learn igmp on a device that doesn't have any IGMP enabled VRFs.

• output

Issue while building the feature

Traceback (most recent call last):
  File "src/genie/cli/commands/learn.py", line 365, in genie.cli.commands.learn.LearnCommand._retrieve_ops
  File "/usr/local/lib/python3.12/site-packages/genie/libs/ops/igmp/iosxr/igmp.py", line 201, in learn
    if 'interfaces' not in self.info['vrfs'][vrf]:
                           ~~~~~~~~~~~~~~~~~^^^^^
KeyError: 'Internet'

Expected Behaviour

The command should parse the command output successfully and if there's a VRF that isn't enabled for IGMP it should output an empty dictionary instead.

Fix

Replace lines 198-202 with

             if 'vrfs' not in self.info:
                 self.info['vrfs'] = {}

             if vrf not in self.info['vrfs']:
                 self.info['vrfs'][vrf] = {}
             
             if 'interfaces' not in self.info['vrfs'][vrf]:
                 self.info['vrfs'][vrf]['interfaces'] = {}

The first if statement, although not strictly necessary initialises the vrfs key if it is not already present.
The second one, initialises a nested VRF under the vrfs key, if it's not present already. This is required if a VRF is not enabled for IGMP.
The last if statement initialises the interfaces key. This again is required if a VRF is not enabled for IGMP and has no IGMP enabled interfaces.

Once the patch is applied learn igmp completes successfully and works as expected.

I have only pasted the output for the Internet VRF for brevity.

      "Internet": {
        "interfaces": {}
      },

Let me know if you'd like me to raise a PR with this fix.