bash_env.fish

function bash_env --description 'Imports named variables from a bash script'
  # Usage:
  # bash_env script.bash VAR1 VAR2 VARN
  #
  set -l script $argv[1]
  while read i; set code "$code""$i"\n; end < $script
  set -l variables
  for arg in $argv[2..-1]
    set variables $variables "echo \"set -g $arg \${$arg}\""\n
  end
  set code "$code""$variables"
  set res (bash -c $code)
  echo "Importing" (count $res) "variable(s)"
  for val in $res
      echo "$val"
      eval "$val"
  end
end

$ echo "export VAR_ONE=1; export VAR_TWO=2" > vars.bash
$ echo $VAR_ONE ; echo $VAR_TWO


$ bash_env vars.bash VAR_ONE VAR_TWO
Importing 2 variable(s)
set -g VAR_ONE 1
set -g VAR_TWO 2
$ echo $VAR_ONE ; echo $VAR_TWO
1
2