Summary

Make fboss2 show interface phymap handle platforms without an external PHY (XPHY) or MACsec-capable PHY ports as a supported empty result.

The command now checks the QsfpService MACsec-capable port list before requesting the MACsec PHY map. When the list is empty, it returns the existing user-facing result:

No Phy port map for this platform

Root cause

CmdShowInterfacePhymap::queryClient() unconditionally called macsecGetPhyPortInfo(). QsfpService protects that RPC with validateHandler(), which throws FbossError("Macsec handler not initialized") when the platform did not create a MACsec handler.

That is expected on platforms such as Cisco C8501 / Morgan800CC, which do not have an XPHY. The CLI treated a supported platform capability difference as a command failure.

Fix details and compatibility

• Query getMacsecCapablePorts() first. This API returns an empty list when there is no PHY manager or no PHY port advertising the MACsec feature.
• Call macsecGetPhyPortInfo() only when at least one MACsec-capable port exists.
• Reuse the existing empty-model output instead of matching exception strings.
• No Thrift API or server behavior changes are required.
• Platforms with MACsec-capable XPHY ports continue through the existing PHY-map RPC and rendering path.

Unit-test coverage

• Added CmdShowInterfacePhymapTest.noXphyPlatform with a mocked empty MACsec-capable port list.
• The test verifies that query execution succeeds, the returned model has no PHY map, and output is exactly No Phy port map for this platform.
• Added the test to both BUCK and CMake FBOSS CLI test targets.

Test Plan

• pre-commit run --from-ref upstream/main --to-ref HEAD — passed, including clang-format and repository checks.
• Built a full C8501 FBOSS image carrying the equivalent backport: fboss-gr2-stable-20260903-fbc276b.1-1-ge405635.
• Validated on a Cisco C8501 / Morgan800CC lab switch.

Before:

$ fboss2 show interface phymap
Thrift call failed: 'Macsec handler not initialized'

After:

$ fboss2 show interface phymap
No Phy port map for this platform

• The fixed command exited with status 0 in 32 ms.
• Confirmed fboss_sw_agent, fboss_hw_agent@0, and qsfp_service remained active after validation.