Documentation for list_parameters (#2315)

* list_parameters documentation

Signed-off-by: CursedRock17 <mtglucas1@gmail.com>

rclcpp/include/rclcpp/node.hpp

@@ -972,7 +972,16 @@ class Node : public std::enable_shared_from_this<Node>
 
   /// Return a list of parameters with any of the given prefixes, up to the given depth.
   /**
-   * \todo: properly document and test this method.
+   * Parameters are separated into a hierarchy using the "." (dot) character.
+   * The "prefixes" argument is a way to select only particular parts of the hierarchy.
+   *
+   * \param[in] prefixes The list of prefixes that should be searched for within the
+   * current parameters. If this vector of prefixes is empty, then list_parameters
+   * will return all parameters.
+   * \param[in] depth An unsigned integer that represents the recursive depth to search.
+   * If this depth = 0, then all parameters that fit the prefixes will be returned.
+   * \returns A ListParametersResult message which contains both an array of unique prefixes
+   * and an array of names that were matched to the prefixes given.
    */
   RCLCPP_PUBLIC
   rcl_interfaces::msg::ListParametersResult

rclcpp/test/rclcpp/node_interfaces/test_node_parameters.cpp

@@ -116,6 +116,13 @@ TEST_F(TestNodeParameters, list_parameters)
   EXPECT_NE(
     std::find(list_result4.names.begin(), list_result4.names.end(), parameter_name),
     list_result4.names.end());
+
+  // Return all parameters when the depth = 0
+  auto list_result5 = node_parameters->list_parameters(prefixes, 0u);
+  EXPECT_EQ(1u, list_result5.names.size());
+  EXPECT_NE(
+    std::find(list_result5.names.begin(), list_result5.names.end(), parameter_name),
+    list_result5.names.end());
 }
 
 TEST_F(TestNodeParameters, parameter_overrides)