No way to reference non top-level keys in parameters map

[solonovamax]

There is no way to reference a non top-level key in a parameter map

Here is an example:

example:
  nested:
    entries:
      type: string_array

    __map_entries:
      value:
        type: string

this does not properly find the entries key, and instead generates code that looks like the following:

// error: no member named 'entries' in 'example::Params'
for (const auto & value_1 : updated_params.entries) {
//                          ~~~~~~~~~~~~~~ ^

    /* ... */
}

the following also does not work:

example:
  nested:
    keys:
      type: string_array

    __map_nested.keys:
      value:
        type: string

as it will generate code that looks like the following:

struct Params {
    struct Nested {
        std::vector<std::string> keys;
// error: expected member name or ';' after declaration specifiers
        struct MapNested.Keys {
//      ~~~~~~~~~~~~~~~~^
            std::string value;
        };
// error: expected '>'
// error: expected member name or ';' after declaration specifiers
        std::map<std::string, MapNested.Keys> nested_keys_map;
//                                     ^
    } nested;
    // for detecting if the parameter struct has been updated
    rclcpp::Time __stamp;
};

/* ... */

// error: invalid range expression of type 'struct Nested'; no viable 'begin' function available
for (const auto & value_1 : updated_params.nested) {
//                        ^ ~~~~~~~~~~~~~~

// error: no member named '__map_nested' in 'example::Params::Nested'
    auto& entry = updated_params.nested.__map_nested.nested_map[value_1];
//                ~~~~~~~~~~~~~~~~~~~~~ ^

    /* ... */
}