[TMUX/ZSH] Venv improvements

zsh/.virtual_env_config.zsh_mac.example

@@ -10,6 +10,20 @@ export VIRTUALENVWRAPPER_VIRTUALENV=$PREFIX/bin/virtualenv
 mkdir -p $WORKON_HOME
 source $PREFIX/bin/virtualenvwrapper.sh
 
-if [ -n "$VIRTUAL_ENV" ] && [[ -f "$VIRTUAL_ENV/bin/activate" ]]; then
-      source $VIRTUAL_ENV/bin/activate;
-fi
+# NOTE: an inherited VIRTUAL_ENV is *not* re-activated here — that happens at the
+# very end of .zshrc so activate captures the fully-built PATH (see the comment
+# there). Sourcing virtualenvwrapper.sh above only defines workon/deactivate/etc.
+
+# Mirror the current venv into a per-pane tmux option so that splitting a pane
+# can carry it into the new pane (.tmux.conf reads #{@venv} with `-e`). Per-pane
+# (not session) state is what lets two panes hold different venvs and lets new
+# *windows* start clean. Only fork tmux when the value actually changes.
+_venv_track_precmd() {
+    [[ -n $TMUX ]] || return
+    if [[ "${VIRTUAL_ENV:-}" != "${_LAST_TRACKED_VENV-unset}" ]]; then
+        tmux set -p @venv "${VIRTUAL_ENV:-}" 2>/dev/null
+        _LAST_TRACKED_VENV="${VIRTUAL_ENV:-}"
+    fi
+}
+autoload -Uz add-zsh-hook
+add-zsh-hook precmd _venv_track_precmd