node: keep the interface path in the regenerated A2A agent card

[vbcherepanov]

Fixes #673.

The caller's node set every HTTP interface in the regenerated card to the service root, so an agent that serves JSON-RPC at /invoke (the a2a-go samples) or HTTP+JSON under /a2a/rest was unreachable through the mesh.

• Provider: A2AService rewrites each JSONRPC or HTTP+JSON interface under target_url to a relative reference (invoke, a2a/rest, or "") when it relays the card.
• Caller: meshInterfaceURL resolves that reference under the mesh URL. An absolute URL, a URL outside the target path, or a reference with a dot segment, a leading /, a scheme or a host maps to the service root as before, so mixed node versions behave as today and a provider cannot point the caller at another path on the caller's node.

Tests: new unit tests in a2a_service_test.go; TestA2ACUJ now serves the agent at /invoke (404 on main, passes with the change). Through two nodes the A2A TCK (263b9cf, Python reference SUT) goes from 77 to 122 passed. go test -race ./... and the integration suite pass on Linux; golangci-lint reports 0 issues.

The Python and JS SDKs rewrite the card the same way; they are not changed here.

[gemini-code-assist]

Code Review

This pull request updates the A2A service to preserve sub-paths of agent interfaces (such as /invoke or /rest) below the mesh path when regenerating agent cards, rather than pointing all interfaces to the bare service root. It introduces response modification in the reverse proxy to relativize the URLs in the agent card, along with validation to prevent directory traversal or external redirects. Unit and integration tests, as well as documentation, have been updated accordingly. Feedback focuses on aligning with the repository style guide: specifically, logging a warning when skipping relativization due to compressed responses (Section 6) and ensuring test assertions explicitly print both observed and expected values (Section 3).

[gemini-code-assist]

3. Test coverage must follow the pyramid

The assertion message does not state both the observed and the expected value, which violates the repository style guide (Section 3, Rule 8). Please update the assertion to explicitly print both.

Suggested change

	if len(card.SupportedInterfaces) != 1 || card.SupportedInterfaces[0].URL != meshBase+"/invoke" {
	t.Errorf("interfaces not regenerated / gRPC not dropped: %+v", card.SupportedInterfaces)
	}
	if len(card.SupportedInterfaces) != 1 || card.SupportedInterfaces[0].URL != meshBase+"/invoke" {
	t.Errorf("interfaces not regenerated / gRPC not dropped: got %+v, want exactly one interface with URL %q", card.SupportedInterfaces, meshBase+"/invoke")
	}

References

1. Section 3, Rule 8: Tests are plain Go on the standard testing package... Flag assertion messages that do not state both the observed and the expected value. ^(link)

[aojea]

need to rebase also we like to have good visibility on errors #677 (comment) otherwise in a p2p network is hard to debug problems, that comment from the bot reviewer is legit

[vbcherepanov]

Rebased on main. A compressed card is now logged ([A2A] agent card of %q is compressed (%s), relayed with its interface URLs unchanged) instead of being skipped silently, and the integration assertion prints both values. Thanks for the review.

[aojea]

I just realized the e2e test added previously with streaming was not exercising the datapath https://github.com/google/agentmesh/compare/7390b7164c778df87855fdf4b423faeadf54472b..b9857a221d98f2e230d6174acc0980837d8d725a

[aojea]

sdk/js (rewriteAgentCardinsdk/js/src/libp2p-http.ts) and sdk/python (rewrite_agent_cardinsdk/python/src/agent_mesh/libp2p_http.py) still overwrite iface.url = base`, let's follow up with the same relative subpath resolution in another commit so we merge all fixes together

[vbcherepanov]

Added the SDK side in the same PR: rewriteAgentCard (JS) and rewrite_agent_card (Python) now resolve the provider's relative reference under the mesh URL with the node's rules, and the JS and Python tests carry the cases of TestMeshInterfaceURLStaysInService and TestA2AServiceCardKeepsInterfacePaths. I also checked both against the Go meshInterfaceURL on 400k random inputs, with no differences. JS 129/129, Python 168 passed on 3.12, go test ./internal/node/ ok. One thing left as before: an SDK member acting as a provider does not relativize its own card yet, so a Go caller still sees the service root for it. Happy to add that in a follow-up if you want it.

[aojea]

Thanks

[aojea]

One thing left as before: an SDK member acting as a provider does not relativize its own card yet, so a Go caller still sees the service root for it. Happy to add that in a follow-up if you want it.

sure, remember to add an integration or e2e test that validates the full code path and datapath ... integration test are faster ...