Zero width control characters insert spaces with shell ex commands

[atommclain]

• Neovim version: 9a3b7fa
• Operating system: Gentoo 2.2
• Terminal emulator: iTerm 2.1.1 (connected to remote system)

Discovered while researching #4142 and #2958

Running a shell command that echoes multiple bell symbols followed by text shifts text to the right.

Actual behaviour

Text preceded by zero width control bell character is shifted to the right.

Expected behaviour

Text should start in the first column.

Steps to reproduce

nvim -u NONE
:!echo -en '\x07\x07\x07\x07text'
// prints
    text
// instead of
text

vim 7.4.769 with same configuration exhibits expected behavior

[justinmk]

#7844 outputs bell chars as ^G.

:!echo -en '\x07\x07\x07\x07text'
^G^G^G^Gtext

This is a design decision.

[bfredl]

The only design decision in #7488 is that we actually can determine what happens on each control char. We could easily change it emit bell, just add it to the list of bytes sent directly to msg_putc (just as ^M was changed)

[justinmk]

Would that work for other control codes like colors? Currently colors are rendered as hl-SpecialChar. E.g. :!bash -i:

^[[0;30m^[[47mSSH^[[0m ^[[0;32mjustin@foo ^[[36m~/foo^[[0m^[[0;33m (test u=)^[[0m

[bfredl]

It is a question of effort. Supporting bell is a trivial one-line change (message.c already supports it, we just need to ask it), so we could just as well do it now, while colors requires implementing or integrating a ANSI control code parser. And the such parser we should (eventually) integrate is :terminal.