[YAML Parser] Support parameter value parsing (ros2#471)

* Support parameter YAML string value parsing.

Signed-off-by: Michel Hidalgo <michel@ekumenlabs.com>

* Address peer review comments.

- Improve test coverage using new getter API.
- Unify function return style and improve readability.

Signed-off-by: Michel Hidalgo <michel@ekumenlabs.com>

* Clean up allocations in rcl_yaml_param_parser package tests.

Signed-off-by: Michel Hidalgo <michel@ekumenlabs.com>

rcl_yaml_param_parser/CMakeLists.txt

@@ -49,6 +49,7 @@ install(TARGETS ${PROJECT_NAME}
 if(BUILD_TESTING)
   find_package(ament_cmake_gtest REQUIRED)
   find_package(ament_lint_auto REQUIRED)
+  find_package(osrf_testing_tools_cpp REQUIRED)
   ament_lint_auto_find_test_dependencies()
 
   # Gtests
@@ -57,6 +58,8 @@ if(BUILD_TESTING)
   )
   if(TARGET test_parse_yaml)
     target_link_libraries(test_parse_yaml ${PROJECT_NAME})
+    target_include_directories(test_parse_yaml
+      PRIVATE ${osrf_testing_tools_cpp_INCLUDE_DIRS})
   endif()
 
 endif()

rcl_yaml_param_parser/include/rcl_yaml_param_parser/parser.h

@@ -25,28 +25,53 @@ extern "C"
 {
 #endif
 
-/// \brief Init param structure
+/// \brief Initialize parameter structure
 /// \param[in] allocator memory allocator to be used
 /// \return a pointer to param structure on success or NULL on failure
 RCL_YAML_PARAM_PARSER_PUBLIC
 rcl_params_t * rcl_yaml_node_struct_init(
   const rcutils_allocator_t allocator);
 
-/// \brief Free param structure
-/// \param[in] params_st points to the populated paramter struct
+/// \brief Free parameter structure
+/// \param[in] params_st points to the populated parameter struct
 RCL_YAML_PARAM_PARSER_PUBLIC
 void rcl_yaml_node_struct_fini(
   rcl_params_t * params_st);
 
 /// \brief Parse the YAML file, initialize and populate params_st
 /// \param[in] file_path is the path to the YAML file
-/// \param[inout] params_st points to the populated paramter struct
+/// \param[inout] params_st points to the populated parameter struct
 /// \return true on success and false on failure
 RCL_YAML_PARAM_PARSER_PUBLIC
 bool rcl_parse_yaml_file(
   const char * file_path,
   rcl_params_t * params_st);
 
+/// \brief Parse a parameter value as a YAML string, updating params_st accordingly
+/// \param[in] node_name is the name of the node to which the parameter belongs
+/// \param[in] param_name is the name of the parameter whose value will be parsed
+/// \param[in] yaml_value is the parameter value as a YAML string to be parsed
+/// \param[inout] params_st points to the parameter struct
+/// \return true on success and false on failure
+RCL_YAML_PARAM_PARSER_PUBLIC
+bool rcl_parse_yaml_value(
+  const char * node_name,
+  const char * param_name,
+  const char * yaml_value,
+  rcl_params_t * params_st);
+
+/// \brief Get the variant value for a given parameter, zero initializing it in the
+/// process if not present already
+/// \param[in] node_name is the name of the node to which the parameter belongs
+/// \param[in] param_name is the name of the parameter whose value is to be retrieved
+/// \param[inout] params_st points to the populated (or to be populated) parameter struct
+/// \return parameter variant value on success and NULL on failure
+RCL_YAML_PARAM_PARSER_PUBLIC
+rcl_variant_t * rcl_yaml_node_struct_get(
+  const char * node_name,
+  const char * param_name,
+  rcl_params_t * params_st);
+
 /// \brief Print the parameter structure to stdout
 /// \param[in] params_st points to the populated parameter struct
 RCL_YAML_PARAM_PARSER_PUBLIC

rcl_yaml_param_parser/package.xml

@@ -16,6 +16,7 @@
   <test_depend>ament_cmake_gtest</test_depend>
   <test_depend>ament_lint_common</test_depend>
   <test_depend>ament_lint_auto</test_depend>
+  <test_depend>osrf_testing_tools_cpp</test_depend>
 
   <export>
     <build_type>ament_cmake</build_type>