Message management for running with signac flow directives

[PheelyC]

Feature description

At the moment when running with operation directives or command line option, the Environment messages are printed each time and the progress bar is forced to start a new line as shown below.

I would like to have a silent option that controls the signac flow messages that are not part of the progress bar, such that the bar can be static.

[bdice]

@PheelyC Can you confirm if this happens with the "fork" directive disabled? We discussed enabling "fork" for your application on Slack, so I wonder if it's due to output from the forked process.

[PheelyC]

Upon further testing, I found that other directives than fork do not generate the issue, however, if I use the timeout option (run -t num) in the command line as I run, the issue comes up.

[bdice]

@PheelyC There are some options like timeout that require forking — the fork directive can force execution in a subprocess, but setting fork=False isn’t guaranteed to avoid forking if other options require it. That would explain why you’re seeing the messages in both of those cases. 👍

https://docs.signac.io/projects/flow/en/latest/api.html?highlight=Fork#flow.directives

Copying the current docs here for posterity (we are reworking this portion of the docs):

The fork directive can be set to True to enforce that a particular operation is always executed within a subprocess and not within the Python interpreter’s process even if there are no other reasons that would prevent that.
Note:
Setting fork=False will not prevent forking if there are other reasons for forking, such as a timeout.