RewrittenYaml does not parse integers keys

[mrmara]

Bug report

• Operating System:
  • Ubuntu 22.04
• ROS2 Version:
  • Humble binaries
• Version or commit hash:
  -Nav2 from source: 30a14090847be6f51f6cd60cbc400a0e4ac38b44
• DDS implementation:
  • Cyclone

Steps to reproduce issue

RewrittenYaml method cannot properly parse yaml files with integers as key, e.g.:

node_number: 3
       0:
          node_name: "NODE1"
          node_frequency: 50
          diagnostic_message_enable: true
       1:
          node_name: "NODE2"
          node_frequency: 20
          diagnostic_message_enable: true
       2:
           node_name: "NODE3"
           node_frequency: 20
           diagnostic_message_enable: true

Expected behavior

RewrittenYaml() properly parse file and does not throw error

Actual behavior

Following error in thrown:

  File "/home/antoniomarangi/ws/install/nav2_common/local/lib/python3.10/dist-packages/nav2_common/launch/rewritten_yaml.py", line 89, in perform
    self.substitute_params(data, param_rewrites)
  File "/home/antoniomarangi/ws/install/nav2_common/local/lib/python3.10/dist-packages/nav2_common/launch/rewritten_yaml.py", line 116, in substitute_params
    yaml_paths = self.pathify(yaml)
  File "/home/antoniomarangi/ws/install/nav2_common/local/lib/python3.10/dist-packages/nav2_common/launch/rewritten_yaml.py", line 156, in pathify
    self.pathify(d, "", paths, joinchar=joinchar)
  File "/home/antoniomarangi/ws/install/nav2_common/local/lib/python3.10/dist-packages/nav2_common/launch/rewritten_yaml.py", line 164, in pathify
    self.pathify(v, pn + k, paths, joinchar=joinchar)
  File "/home/antoniomarangi/ws/install/nav2_common/local/lib/python3.10/dist-packages/nav2_common/launch/rewritten_yaml.py", line 164, in pathify
    self.pathify(v, pn + k, paths, joinchar=joinchar)
  File "/home/antoniomarangi/ws/install/nav2_common/local/lib/python3.10/dist-packages/nav2_common/launch/rewritten_yaml.py", line 164, in pathify
    self.pathify(v, pn + k, paths, joinchar=joinchar)
  [Previous line repeated 3 more times]
TypeError: can only concatenate str (not "int") to str

[ERROR] [launch]: Caught exception in launch (see debug for traceback): can only concatenate str (not "int") to str

---

Feature description

I do not know if using integers as key is a best practice or not, but is allowed by yaml format.
Moreover, it is really practical when the number of certain parameters is known a priori but can frequently change, e.g.:

// Declare parameters
get_parameter("node_number", node_number);
  for (int i = 0; i < node_number; i++)
  {
    std::string node_item = "nodes." + std::to_string(i);
		this->declare_parameter(node_item + ".node_name", "no_name"); 
    this->declare_parameter(node_item + ".node_frequency", 10);
    this->declare_parameter(node_item + ".diagnostic_message_enable", false);
}
  // Get parameters and store them
  for (int i = 0; i < node_number; i++)
  {
    std::string node_item = "nodes." + std::to_string(i);
    NodeParams np;
    get_parameter<std::string>(node_item + ".node_name", np.node_name);
    get_parameter<int>(node_item + ".node_frequency", np.node_frequency);
    get_parameter<bool>(node_item + ".diagnostic_message_enable", np.diagnostic_message_enable);
}

Implementation considerations

A fix could consist in str casting inside RewrittenYaml.pathify()
In particulat cast to str pn and k as long with idx

def pathify(self, d, p=None, paths=None, joinchar='.'):
        if p is None:
            paths = {}
            self.pathify(d, "", paths, joinchar=joinchar)
            return paths
        pn = p
        if p != "":
            pn += joinchar
        if isinstance(d, dict):
            for k in d:
                v = d[k]
-------->    self.pathify(v, str(pn) + str(k), paths, joinchar=joinchar) <---------------------
        elif isinstance(d, list):
            for idx, e in enumerate(d):
                self.pathify(e, pn + str(idx), paths, joinchar=joinchar)
        else:
            paths[p] = d

[SteveMacenski]

Hi!

I would say that ints as keys are probably not a great solutions in my personal opinion but there’s nothing wrong with it. What you suggest is reasonable, can you open a PR? Happy to merge the change!

[mrmara]

I will test the solution to make sure everything is fine and prepare the PR.

Thanks for the support