How to get pre- and post- command execution notifications working in ShellEditor?

[Daniel Farrell]

Hello all,

I've put together an example here https://stackoverflow.com/questions/76371852/using-traitsui-shelleditor-to-get-notifications-before-and-after-the-user-hits-t

ShellEditor seems to expose `command_executed` and `command_to_execute` extended trait attributes. You can supply to them a string of a trait on your object and when the user types something in the embedded Python shell they will get a notification. However, only post-command notification (command_executed) fires. The pre-command notification does not seem to work.

For example,

    ShellEditor(

        share=False,

        command_executed="did_execute_command",

         command_to_execute="will_execute_command"  # never notified

     )

A full working example is shown via the link above.

Regards,

Dan