asdf which extension - adds an option to specify a version as the third arg to the which subcommand and get a path the binary

asdf_which.sh

# (Paste into your bash .profile or whatever you use)
#
#   $ asdf which python
#   /Users/jstroop/.asdf/installs/python/3.8.5/bin/python # version in .tool-versions
#   $ asdf which python 3.7.6
#   /Users/jstroop/.asdf/installs/python/3.7.6/bin/python # version from 3rd arg
#
# NOTE: Python < 3.11-dev does not compile on Apple silicon.
#       See: https://bugs.python.org/issue43878. 
#       Use Rosetta if necessary.
#
## For Homebrew on macOS
. $(brew --prefix asdf)/libexec/asdf.sh
. $(brew --prefix)/etc/bash_completion.d/asdf.bash

ASDF_LANGS=("python" "ruby") # may need expansion for other langs.
function asdf() {
  if [[ "$1" == "which" && "${ASDF_LANGS[@]}" =~ "${2}" && "$3" != "" ]]; then
    shift 1
    where=$(asdf where $1 $2)
    if [[ "$where" == "Version not installed" ]]; then
      command echo $where
    else
      command echo $where/bin/$1
    fi
  else
    command asdf "$@"
  fi
}