Weird output when running a system command with vim.cmd via a mapping

[mihaifm]

Problem

When using a mapping to run a system command, the first row of the output is mixed with the command name.

Steps to reproduce

nvim --clean
:lua vim.keymap.set('n', 'gz', function() vim.cmd('!echo abc') end)

Press gz

Output:

abccho abc

Expected behavior

Expected output (which is shown when running the command directly):

:!echo abc
abc

Neovim version (nvim -v)

NVIM v0.10.0-dev-3036+gab1c2220f

Vim (not Nvim) behaves the same?

no

Operating system/version

linux, windows

Terminal name/version

all terminals

$TERM environment variable

Installation

binary

[zeertzjq]

Related #22878

[mihaifm]

Strangely I get the same behavior by running

:execute "normal :!echo abc\n"

In Vim this doesn't keep the popup open, so I guess it's still a Neovim issue.

[zeertzjq]

Hmm, that happens with :execute "normal :echo 111 | echo 222\n" too.

[zeertzjq]

Also related: #20673