tempname() fails when NVIM_APPNAME is set to subdirectory

[Subjective]

Problem

When NVIM_APPNAME contains a subdirectory, tempname() fails to return anything. For example, I store all of my nvim configs in $HOME/nvim-profiles and use an alias to run nvim with the the NVIM_APPNAME variable set. However, any plugins that rely on tempname() to generate a temporary directory are not able to run properly.

Before NVIM_APPNAME, I just set the various XDG_HOME variables using the following shell script, and everything worked fine:

Shell Script

#!/bin/sh
NVIM_PROFILE_NAME=""
NVIM_COMMAND="nvim"

exec env XDG_CONFIG_HOME="$HOME/.config/nvim-profiles/${NVIM_PROFILE_NAME}" \
         XDG_DATA_HOME="$HOME/.local/share/nvim-profiles/${NVIM_PROFILE_NAME}" \
         XDG_STATE_HOME="$HOME/.local/state/nvim-profiles/${NVIM_PROFILE_NAME}" \
         XDG_CACHE_HOME="$HOME/.cache/nvim-profiles/${NVIM_PROFILE_NAME}" \
         ${NVIM_COMMAND} \
         "$@"

Steps to reproduce

1. Run the following commands in terminal

cd $HOME
NVIM_APPNAME="some_directory/TestVim" nvim

2. execute "echo tempname()" in neovim
3. Nothing gets returned
4. Run NVIM_APPNAME="TestVim" nvim
5. tempname() returns a temporary directory path

Expected behavior

I would expect tempname() to return the path to a temporary directory:

Interestingly enough, calling the alias in the ~/.local/state directory allows tempname() to return a directory. No clue why this happens.

Neovim version (nvim -v)

NVIM v0.10.0-dev-46+ge23c6ebed

Vim (not Nvim) behaves the same?

no

Operating system/version

macOS 13.3

Terminal name/version

Kitty 0.27.1

$TERM environment variable

xterm-kitty

Installation

bob

[bfredl]

as of 0.9, NVIM_APPNAME only supports, well, a name, not a full path, which was never intended. The simplest solution would be to add a proper error message for this instead of random errors down the line, as you get now.