[Bug 1768798] Re: netplan try: terminal does not echo keypresses after ^C during wait

[Steve Langasek]

** Changed in: netplan.io (Ubuntu Bionic)
       Status: Fix Released => Fix Committed

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https://bugs.launchpad.net/bugs/1768798

Title:
  netplan try: terminal does not echo keypresses after ^C during wait

Status in netplan.io package in Ubuntu:
  Fix Released
Status in netplan.io source package in Bionic:
  Fix Committed

Bug description:
  [Impact]
  All netplan users.

  [Test case]
  1) Run 'sudo netplan try' to "try" a new netplan config.
  2) Hit Control-C during the timer, to escape to the terminal without applying the configuration.

  Validate that text typed on the terminal after hitting Control-C is
  correctly echoed on screen.

  [Regression Potential]
  Some non-standard shells may behave differently with the console and expect a specific set of modes. Care has been taken to correctly record and restore the original terminal modes and flags, as well as testing on bash, dash, zsh, in a text VT, etc; but it is possible for non-standard terminals to misunderstand the mode changes and thus incorrectly handle Control-C or other mode changes required by 'netplan try' leading to failure to echo characters, mishandling carriage returns, clears, or invalid color schemes on terminal.

  --

  If I do netplan try, press ^C during the wait, and try to type, my
  characters are not echoed to the terminal.

  (This is similar to what powersj found in
  https://asciinema.org/a/176782 but different in that instead of Enter
  it's ^C that triggers it.)

  I think you'll need to trap KeyboardInterrupt exceptions and reset
  afterwards? or use a try/finally construct to make sure things are
  reset?

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