append-tee.zsh

next-output-file-name () {
  base="$1"
  for ((i=0; i<20; i++)); do
    filename="${base}.${i}"
    [[ ! -e "$filename" ]] && print "$filename" && return
  done
  print "ERROR"
}

append-tee-file-base () {
  case "$BUFFER" in
    *apply*) print 'apply.out' ;;
    *check*) print 'check.out' ;;
    *plan*)  print 'plan.out' ;;
    *terraform*init*) print 'init.out' ;;
    *test*) print 'test.out' ;;
    *)
      cmd="${${(z)BUFFER}[1]}"
      print "${cmd:-x}.out"
  esac
  set +x
}

append-tee-command () {
  output_base="$(append-tee-file-base "$cmd")"
  output_filename="$(next-output-file-name "$output_base")"
  print "tee ${output_filename}"
}

append-tee () {
  BUFFER="${LBUFFER}|& $(append-tee-command "$cmd")${RBUFFER}"
  ((CURSOR = $#BUFFER))
}

zle -N append-tee
# option-t on macOS
bindkey † append-tee
# if not on macOS
bindkey "^X^t" append-tee