Bash - File local variables - prompt

Question

I just wrote a small file to set my PS1 variable. This file is sourced from my .bashrc. Now I have a couple of questions regarding this approach.
But first the code:
setprompt:
# Normal variables
BOLD="$(tput bold)"
RESET="$(tput sgr0)"
RED="$(tput setaf 1)"
GREEN="$(tput setaf 2)"
YELLOW="$(tput setaf 3)"
BLUE="$(tput setaf 4)"
PINK="$(tput setaf 5)"
CYAN="$(tput setaf 6)"
GRAY="$(tput setaf 7)"
# Make non-printable variables
PROMPT_BOLD="\[$BOLD\]"
PROMPT_RESET="\[$RESET\]"
PROMPT_RED="\[$RED\]"
PROMPT_GREEN="\[$GREEN\]"
PROMPT_YELLOW="\[$YELLOW\]"
PROMPT_BLUE="\[$BLUE\]"
PROMPT_PINK="\[$PINK\]"
PROMPT_CYAN="\[$CYAN\]"
PROMPT_GRAY="\[$GRAY\]"
# Other variables
USERNAME="\u"
FULL_HOSTNAME="\H"
SHORT_HOSTNAME="\h"
FULL_WORKING_DIR="\w"
BASE_WORKING_DIR="\W"
# Throw it together
FINAL="${PROMPT_RESET}${PROMPT_BOLD}${PROMPT_GREEN}"
FINAL+="${USERNAME}#${SHORT_HOSTNAME} "
FINAL+="${PROMPT_RED}${FULL_WORKING_DIR}\$ "
FINAL+="${PROMPT_RESET}"
# Export variable
export PS1="${FINAL}"
.bashrc:
..
source ~/.dotfiles/other/setprompt
..
My questions:
Will this approach slow down my bash startup? Should I just write one ugly unreadable line of code instead of doing these variable definitions/sourcing?
I noticed, that the variables defined in setprompt are still defined in my .bashrc. I don't like this behaviour since it's not obvious to the editor of .bashrc that variables are defined when sourcing setprompt. Is this just the behaviour of source? What can I do about this?
Edit:
This is the approach I use now (recommended by tripleee):
getPrompt.sh:
#!/bin/bash
getPrompt () {
# Bold/Reset
local PROMPT_BOLD="\[$(tput bold)\]"
local PROMPT_RESET="\[$(tput sgr0)\]"
# Colors
local PROMPT_RED="\[$(tput setaf 1)\]"
local PROMPT_GREEN="\[$(tput setaf 2)\]"
# Miscellaneous
local USERNAME="\u" local SHORT_HOSTNAME="\h"
local FULL_WORKING_DIR="\w"
# Print for later use
printf "%s%s%s%s" "${PROMPT_RESET}${PROMPT_BOLD}${PROMPT_GREEN}" \
"${USERNAME}#${SHORT_HOSTNAME} " \
"${PROMPT_RED}${FULL_WORKING_DIR}\$ " \
"${PROMPT_RESET}"
}
.bashrc:
source ~/.dotfiles/bash/getPrompt.sh
PS1=$(getPrompt)

Answer 1

Keeping things human-readable is probably a good thing, and if performance is a problem, perhaps you can control whether this gets executed at all if your prompt is already set. As a first step, maybe move the call to .bash_profile instead of .bashrc.
You can either unset all the variables at the end of the script, or refactor the script so that it runs as a function, or as a separate script (i.e. call it instead of source it).
If you put it all in a function, the function will need to declare all the variables local.
If you run this as an external script, you will need to change it so that it prints the final value. Then you can call it like
PS1=$(setprompt)
without any side effects. (Perhaps you would want to do this with a function, too, just to keep it clean and modular.)