How to auto-complete a multi-level command aliased to a single command? - bash

Question

Say I have two bash functions:
dock() { sudo docker $# ;}
and
dock-ip() { sudo docker inspect --format '{{ .NetworkSettings.IPAddress }}' $# ;}
How to get bash auto-completion working with the second function?
With the first one, it is as easy as adding:
_completion_loader docker; complete -F _docker dock
This will not work for the second one. The autocomplete source for Docker is in /usr/share/bash-completion/completions/docker on Debian Stretch. I have more functions like dock-run, dock-exec, etc. so I don't want to write a custom completion function for each of them.
Also, complete -F _docker_container_inspect dock-ip only partially works; tab only lists containers, not completes partial strings.
Research:
How do I autocomplete nested, multi-level subcommands? <-- needs custom functions
https://superuser.com/questions/436314/how-can-i-get-bash-to-perform-tab-completion-for-my-aliases <-- automated for top commands only

Answer 1

With a combined hour of bash completion experience, I took apart the docker completion script (/usr/share/bash-completion/completions/docker) and the bash_completion.sh script to come up with a wrapper function:
# Usage:
# docker_alias_completion_wrapper <completion function> <alias/function name>
#
# Example:
# dock-ip() { docker inspect --format '{{ .NetworkSettings.IPAddress }}' $# ;}
# docker_alias_completion_wrapper __docker_complete_containers_running dock-ip
function docker_alias_completion_wrapper {
local completion_function="$1";
local alias_name="$2";
local func=$(cat <<EOT
# Generate a new completion function name
function _$alias_name() {
# Start off like _docker()
local previous_extglob_setting=\$(shopt -p extglob);
shopt -s extglob;
# Populate \$cur, \$prev, \$words, \$cword
_get_comp_words_by_ref -n : cur prev words cword;
# Declare and execute
declare -F $completion_function >/dev/null && $completion_function;
eval "\$previous_extglob_setting";
return 0;
};
EOT
);
eval "$func";
# Register the alias completion function
complete -F _$alias_name $alias_name
}
export -f docker_alias_completion_wrapper
I then created my alias/functions like this:
# Get container IP
dock-ip() { docker inspect --format '{{ .NetworkSettings.IPAddress }}' $# ;}
docker_alias_completion_wrapper __docker_complete_containers_running dock-ip
# Execute interactive container
dock-exec() { docker exec -i -t --privileged $# ;}
docker_alias_completion_wrapper __docker_complete_containers_all dock-exec
...
Be sure to call _completion_loader docker; at the top of your profile aliases script to load the main Docker completion scripts. I invite more skilled bash programmers to improve this answer, please.