How to have completions for a command match that of an empty command line?

[patrick-kidger]

How to have completions for a command match that of an empty command line?

[faho]

This is essentially what the completions for sudo or env do.

In principle, what you need to do is to get mytool run python to complete like python - to do that, you need to run complete -C python.

So, you need to grab the commandline, and remove "mytool run" from it.

Fish has the __fish_complete_subcommand helper function for this, and in the simplest case this would be

complete --command mytool -n "__fish_seen_subcommand_from run" -a '$(__fish_complete_subcommand --fcs-skip=2)'

where the "--fcs-skip=2" tells it to skip two tokens from the commandline - that's "mytool" and "run".

If your tool has e.g. options that come before the "run" this gets more complicated, see the sudo completions and the __fish_sudo_print_remaining_args helper function for how to do that.

---

Your attempt here has two issues:

1. Because "$(complete -C)" is double-quoted, the complete -C will be run when the completions are loaded. That means if you attempt to complete something else, it will be stuck on the initial commandline
2. complete -C reruns completions on the entire current commandline (it's the implied default if you don't give it a "fake" commandline to operate on)

[patrick-kidger]

Aha! This is absolutely perfect.

I also learnt a lot about fish generates completions -- the explanation for how this comes together (I just spent a bit of time fiddling with __fish_complete_subcommand to see how it works) was super useful.

Thank you so much, I really appreciate the help.