Respect termios ECHO flag

[IanManske]

This PR makes it so that the ECHO flag given by termios is respected. That is, the input characters are not printed/echoed back to the user if the ECHO flag is missing. This will help with using rexpect to test reedline and nushell, as the syntax highlighting, etc. does not need to be accounted for.
Related to: nushell/nushell#11178

[IanManske]

In the future, this PR might not be necessary to get rexpect working, since the latest commits introduce a way to ignore escape sequences. So, this can be used instead to get around the syntax highlighting issue once a new rexpect version comes out.

Note that for now, the PR only stops the printing of the input text -- hints, menus, or history will always be shown regardless of the ECHO flag (I think this is the most sane behavior?).

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (93af55c) 49.19% compared to head (56cf8e2) 49.23%.
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #673      +/-   ##
==========================================
+ Coverage   49.19%   49.23%   +0.04%     
==========================================
  Files          46       46              
  Lines        7930     7917      -13     
==========================================
- Hits         3901     3898       -3     
+ Misses       4029     4019      -10     

Files	Coverage Δ
src/engine.rs	5.06% <6.66%> (+0.06%)	⬆️

... and 9 files with indirect coverage changes

[sholderbach]

Not sure what is the best choice to test reedline's specifc behavior with rexpect or what conventions arose for other shells when given ~ECHO.
For your Nushell tests in nushell/nushell#11178 having the hinter dump stuff from the history may possibly interfere.

[sholderbach]

Not super critical but we could make this a unix only dependency for slightly faster downloads on windows.

[IanManske]

Thanks, forgot to do that.

[sholderbach]

As this an absolutely obscure usecase I think expanding this to a small doccomment with pointers what you are trying to achieve and the relation to the termios flag makes sense for future generations.

[IanManske]

For your Nushell tests in nushell/nushell#11178 having the hinter dump stuff from the history may possibly interfere.

Thankfully, I don't think this will be an issue:

• The tests so far only send whole lines, so there shouldn't? be an opportunity for the hints to show.
• rexpect will skip over output until it finds the expected output anyways, so this should include hints. (Syntax highlighting, on the other hand, is interspersed with the output which messes things up).

This is also part of the reason why I was wondering if there was a way to disable the history for nushell or start with a blank history file.

Not sure what is the best choice to test reedline's specifc behavior with rexpect or what conventions arose for other shells when given ~ECHO.

The only example that I know off the top of my head is GNU readline. It takes into account the ECHO flag which is why rexpect doesn't have to expect lines sent to bash.