I was wondering if we could change the session and client environment variables once Kakoune has started.

Having a way to access and change them could be nice to

• set and update Kakoune environment without having to restart Kakoune in a new shell,
• fine-tune tools to Kakoune client-server model.

Kakoune already does some path manipulation (#4433) by prefixing the currently running kak binary in PATH, and it could be a good way to expose shell scripts in Kakoune plugins (#4425).

The proposal is to add

• set-environment [session|client] <name> <value>,
• unset-environment [session|client] <name>
• and %env{name} expansion.

Here is a plugin example with the following files:

bin/:e -> :edit
bin/:edit
bin/:fzf
rc/connect.kak

rc/connect.kak

# Exposes bin in PATH.
set-environment session PATH "%sh{dirname ""$kak_source""}/../bin:%env{PATH}"

# Exposes the session and client environment variables,
# so :edit command has the necessary information to open files in a client/session.
#
# Note: needs a hook to handle session rename.
set-environment session kak_session %val{session}
hook global ClientCreate '.+' %{
  set-environment client kak_client %val{client}
}

bin/:edit

#!/bin/sh

export file
for file do
  echo evaluate-commands -client %env{kak_client} -- edit -- %env{file} |
  kak -p "$kak_session"
  # Note: We use the %env{name} expansion, so we don’t have to “kak quote” values; passing values is straightforward.
  # We expose the `file` environment variable to the `kak` binary, and `kak_client` is already exported.
  #
  # Having `kak -p session_name -args -- 1 2 3` could be nice to pass values in %arg{@} expansion.
done

bin/:fzf

find "$@" -type f | fzf | xargs :edit --

In Kakoune, we can now do:

terminal :fzf

To tune FZF_DEFAULT_OPTS in a client:

set-environment client FZF_DEFAULT_OPTS '--height=40% --layout=reverse --border'

# Similar syntax to `buffer=name` for `set-option`.
set-environment client=client2 FZF_DEFAULT_OPTS '--height=40% --layout=reverse --border'

Assuming we have a Kakoune command to spawn a program, it still convenient for interactive usage without writing a wrapper for every windowing system.

spawn alacritty -e :fzf
spawn tmux split :fzf path/to/dir

Since we have :edit and :fzf in PATH, we can open a terminal from Kakoune and use the commands in the shell.

spawn alacritty

then in the terminal:

:e docs/*.txt
:fzf