[Nexthop][fboss2-dev] fboss2-dev switchport access vlan: validate VLAN exists before commit

[hillol-nexthop]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

fboss2-dev config interface <name> switchport access vlan <id> blindly wrote ingressVlan on the port and rewrote the matching vlanPorts entry without checking that the target VLAN existed in config.sw()->vlans() or that it had a corresponding L3 interface in config.sw()->interfaces(). The CLI then printed Config session committed successfully and triggered a warmboot; fboss_sw_agent SIGABRTed during initialization with:

switch initialization failed: VLAN <id> has no interface, even when corresp port <port> is enabled

Validate both conditions up front in queryClient() and throw std::invalid_argument with a descriptive message before touching the config or saving.

• CmdConfigInterfaceSwitchportAccessVlan.cpp: pre-flight check for VLAN existence + interface presence.
• CmdConfigInterfaceSwitchportAccessVlanTest.cpp: fixture now seeds sw.vlans / sw.interfaces; added negative tests for both rejection paths and assert the running config is unchanged after the throw.

Also removing RestartTest because this is redundant as feature specific tests like access vlan test would do the same thing.

Test plan

• Unit tests: queryClientThrowsWhenVlanDoesNotExist, queryClientThrowsWhenVlanHasNoInterface, plus updated positive case still passes against the seeded VLAN.

[joseph5wu]

The vlan existence check looks good to me but I'm not sure why do we need the vlan to have interfaces before you can set a port with an access vlan? Wouldn't this cli be used to assign the vlan to a port/interface?

[hillol-nexthop]

The vlan existence check looks good to me but I'm not sure why do we need the vlan to have interfaces before you can set a port with an access vlan? Wouldn't this cli be used to assign the vlan to a port/interface?

Yes you are right. I have changed it.