Invalid IDL files generated when IDL reserved keywords are used as field name

[achim-k]

Bug report

Invalid IDL files are generated when IDL reserved keywords are used as field name.

Consider the generated action_tutorials_interfaces/Fibonanni.idl:

    struct Fibonacci_Result {
      sequence<int32> sequence;
    };

sequence cannot be used as the field name as it is a reserved keyword (see https://www.omg.org/spec/IDL/4.2/PDF, page 29 for a list of all keywords)

Required Info:

• Operating System: Ubuntu 22.04
• Installation type: Binaries
• Version or commit hash: 3.1.4-1jammy.20230112.141540
• DDS implementation: N/A
• Client library (if applicable): N/A

Steps to reproduce issue

1. Build action_tutorials_interfaces (or install from binaries)
2. Confirm that the generated Fibonacci.idl file is invalid as it uses the reserved keyword sequence

Expected behavior

IDL generation from msg/srv/action files which use reserved IDL keywords as field names should fail. Parsing for invalid IDL files should also fail.

Actual behavior

IDL generation succeeds

[clalancette]

We discussed this, and what we should have is a check in rosidl_parser to check for this situation early on.

Once we have this detection, there is a design decision to make about what we do in response. We could rename the field (add an _ or something), but that has downstream effects. We could add an IDL annotation to help with that. Or we could reject it out-of-hand and make the user fix it.

While this is definitely a bug, I'm going to put it on our backlog since we probably won't look at this soon.