Enable completion for conda environments with `source activate ...`. Save in /etc/bash_completion.d/

source.sh

# command: source
# Allow autocomplete for conda environments

_complete_source_activate_conda(){
      if [ ${COMP_WORDS[COMP_CWORD-1]} != "activate" ]
      then
          return 0
      fi
      local cur=${COMP_WORDS[COMP_CWORD]}
      COMPREPLY=($(ls ~/anaconda3/envs | xargs -I dirs bash -c "compgen -W dirs $cur"))
      return 0
}

complete -F _complete_source_activate_conda source