fix(gateway): reconstruct nested plugin config from dotted ROS params

[mfaferek93]

Summary

extract_plugin_config() built a flat JSON object keyed by the dotted parameter remainder. For a ROS parameter plugins.<plugin>.native_alarms.enabled it produced {"native_alarms.enabled": true}. Every plugin, however, reads its config as a nested object (config.contains("native_alarms"), config["native_alarms"]["enabled"]), so the lookup always missed.

Effect: the entire plugins.<name>.* ROS-param surface was silently dead for any nested key, across every plugin - native_alarms + discovery, discovery/auto_browse/auto_alarms, severity_bands, and so on. Only single-level keys, node_map YAML, and flat env vars worked; configuring a plugin's nested blocks through gateway parameters had no effect and raised no error.

Fix

Reconstruct a nested JSON object from the dotted keys: after stripping the plugins.<plugin>. prefix, split the remainder on . and build nested objects. Preserved end to end:

• single-level keys stay flat (no change to existing flat config),
• both parameter sources (NodeOptions parameter_overrides and the --params-file YAML via list_parameters),
• array/list leaves kept verbatim,
• the read-only .path key stays excluded.

A key used both as a leaf and an intermediate (e.g. discovery: true and discovery.enabled: true) resolves to the nested object deterministically and warns, never crashing.

The extraction helpers moved into param_utils.hpp so the behavior is unit-testable.

Testing

test_plugin_config gains coverage locking the nested shape: 2-level, 3-level (severity_bands), an array leaf, .path exclusion, and a leaf/intermediate collision. These assertions fail against the old flat implementation. Built and ran the gateway gtests in a ros:jazzy container: test_plugin_config passes (1/1, all cases). clang-format-18 clean.

[Copilot]

Pull request overview

This PR fixes plugin configuration extraction in ros2_medkit_gateway so ROS parameters under plugins.<name>.* correctly reconstruct nested JSON objects from dotted keys (instead of producing a flat JSON map that plugins never match), and adds unit tests to lock in the expected nested shape.

Changes:

• Move extract_plugin_config() (and its helpers) into param_utils.hpp and rebuild nested JSON config by splitting dotted keys into object hierarchies.
• Remove the old flat extraction implementation from gateway_node.cpp and use the shared helper.
• Extend test_plugin_config with cases covering 2-/3-level nesting, array leaves, .path exclusion, and leaf/intermediate collisions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/ros2_medkit_gateway/test/test_plugin_config.cpp	Adds unit coverage asserting nested JSON reconstruction and collision behavior for plugin config extraction.
src/ros2_medkit_gateway/src/gateway_node.cpp	Removes the old flat extract_plugin_config() implementation and uses the shared helper from param_utils.hpp.
src/ros2_medkit_gateway/include/ros2_medkit_gateway/param_utils.hpp	Implements nested insertion for dotted keys and exposes extract_plugin_config() for reuse/testing.

[bburda]

Test coverage gaps (outside the diff):

• Nested reconstruction is only tested through the NodeOptions parameter_overrides source. Both extract_plugin_config tests set overrides, so config is non-empty and the function returns before the --params-file path runs (declare_plugin_params_from_yaml -> list_parameters -> the second insert_nested_param loop). That YAML path is the production one. The existing YAML tests call declare_plugin_params_from_yaml directly and only check flat single-level keys; none call extract_plugin_config. So a regression in the second source (the list_prefix without trailing dot, the substr, the second loop) would produce flat or empty config in production and no test would fail. Worth adding a test that loads nested keys from a --params-file, builds a node with no parameter_overrides, calls extract_plugin_config, and asserts the nested object (with one array leaf).

• The leaf/intermediate collision test only covers one order: scalar first (discovery), then the nested key (discovery.enabled). That path hits the intermediate branch at param_utils.hpp:96-108. The reverse order (nested key first, then the scalar) goes through the leaf guard at param_utils.hpp:113-119, which no test exercises, even though the docstring says the result is the same in either order. Worth adding the reversed case.

[mfaferek93]

Addressed the review-body test-coverage gaps in 3e1c35f:

• YAML source untested: right, both extract_plugin_config tests set overrides and return at source 1, so the --params-file path (declare_plugin_params_from_yaml -> list_parameters -> second insert loop) was never checked. Added ExtractPluginConfigReconstructsNestedFromYaml: loads nested keys from a --params-file, node has no parameter_overrides, calls extract_plugin_config, asserts the 2-/3-level nesting plus an array leaf and .path exclusion.
• Collision only one order: right, scalar-first hit the intermediate branch, the leaf guard was never exercised. Added ExtractPluginConfigLeafIntermediateCollisionReversed (nested key first, scalar second).

Built ros2_medkit_gateway and ran ctest -R test_plugin_config in a clean ros:jazzy container: 7/7 pass.