Only last line of multi-line nvim_out_write appears when sent as notification

[ddickstein]

Problem

When nvim_out_write is called as a notification over RPC, only the last line is displayed.

Steps to reproduce

let sock = sockconnect("pipe", v:servername, { "rpc": 1 })
call rpcnotify(sock, "nvim_out_write", "foo\nbar\nbaz\n")

Expected behavior

I expect the output to be

foo
bar
baz
Press ENTER or type command to continue

but it is instead

baz

There is some possibility that this is by design, but if so this behavior difference needs to be documented (ideally w/ its motivation).

Neovim version (nvim -v)

v0.9.0-dev-1312+g908494889

Vim (not Nvim) behaves the same?

N/A

Operating system/version

Rocky Linux 8.6

Terminal name/version

xfce4-terminal 1.0.4

$TERM environment variable

tmux-256color

Installation

appimage

[zeertzjq]

You can use nvim_echo instead, which doesn't have this problem.

[ddickstein]

This affects the default LSP handler for window/showMessage, which uses nvim_out_write. Should that be changed to nvim_echo while this issue remains open?