Warn if trace directory already exists when using tracing tools/commands about ros2_tracing HOT 3 CLOSED

Well, I see two options:

1. As mentioned above, emit a warning if the trace directory already exists; or
2. Error out (for ros2 trace) or throw an error (for the Trace action) if the trace directory already exists, unless the user uses a new --append/append=True option.

I'd go for option 2. @mjcarroll what do you think?

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I think I would prefer option 2. As you said, you can end up with some weird discontinuities in the data if you appended without realizing it. I would prefer for it to error out and allow me to fix it.

Another option would be to auto-append an integer in the case of a conflict, but I don't know if that's too complicated.

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Thanks for the feedback.

Another option would be to auto-append an integer in the case of a conflict, but I don't know if that's too complicated.

Yeah, I don't think that's a desirable default behaviour, since I think the user expects the given session name to be used as the trace directory name, even if the trace directory path is printed. At least that's what I would expect.

Tangentially, tracetools_trace can append a timestamp to the session name, but it's not exposed by tracetools_trace itself or by ros2trace. It's only used by tracetools_test. We could probably expose it through tracetools_trace/ros2trace (opt-in) separately from this issue.

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