Bash cd package shortcuts with tab completion

packages-completion.sh

#!/usr/bin/env bash
#
# For moving between packages in an npm monorepo
#
# Installation: 
# add `source packages-completion.sh` or the contents of this file to your .bash_profile
#
# Usage:
# While working in a npm monorepo 
#  - `cd_<tab><enter>` to return to the root (unless you have another alias starting with `cd_`)
#  - `pkg package_name<enter>` to change to a package directory
#  - `pkg <tab><tab>` to list all packages
#  - `pkg str<tab>` to complete a package name uniquely starting with `str`
#  - `pkg str<tab><tab>` to list all packages starting with `str`

# print the root directory of the current path
monorepo_rootdir() { 
  pwd | sed -Ee "s:(.*)/packages.*:\1:"
}

# cd into the root
cd_monorepo_rootdir() {
  cd $(monorepo_rootdir)
}

# cd into a specific package dir
pkg() {
  cd_monorepo_rootdir
  cd packages/$*
}

# shell tab completion helper for pkg function
_pkg_completion() {
  # the current input commandline is passed via COMP_WORDS / COMP_CWORD
  # the word currently being typed: 
  local WORD="${COMP_WORDS[COMP_CWORD]}"

  # current working root
  local MONO_ROOT=$(monorepo_rootdir)

  # set possible valid completions in COMPREPLY
  COMPREPLY=( $(/bin/ls -1 "$MONO_ROOT/packages" | grep "$WORD") )
} &&

# set shell tab completion for "pkg"
# -F [function]: run function (1) for invocations of command (2)
complete -F _pkg_completion pkg