Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04 LTS
• Installation type:
  • Binary
• Version or commit hash:
  • galactic
• DDS implementation:
  • Eclipse Cyclone DDS

Steps to reproduce issue

Add a comment like this to any configuration yaml file that is used:

    # $(env NON_EXISTING_ENV_VAR)

and add allow_subst="true" to its referencing param tag:

    <param from="my_config.yaml" allow_substs="true"/>

Expected behavior

The comment should be ignored and it should work as usually.

Actual behavior

Ros tries to resolve the environment variable and crashes if it does not exist, even though it is commented out.