Re: Global Aliases, but as a function?

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

On Sat, Dec 18, 2021 at 2:38 AM Zach Riggle <zachriggle@xxxxxxxxx> wrote:
>
> Is there any way to define something similar to a "global alias" but
> which can modify the original command?
>
> There's a lot of use-cases for this, but the one that I'm wondering
> about specifically is to pass anything with "--help" in the command
> line into a pager that does a best-effort colorization IFF the output
> is not already colored.

The only way to approximate this is by hooking into the ZLE editor to
modify $BUFFER before passing it to the lexer/parser.  (Aliases modify
the single substituted word, during lexical analysis.)

There are a bunch of ways to do this, but mainly there are three
choices, any/all of which involve creating a custom widget:

1/  Explicitly invoke your widget with a key binding.  This gives you
the most flexibility because you can edit the result or undo it.  (In
this case, though, you might instead want to consider using the
run-help binding with a suitable function.)
2/  Override the accept-line widget (or the keybindings for it) with
your custom widget (and then invoke the ".accept-line" widget at the
end).  This may be tricky to get right, and to avoid having it
interfere with other plugins etc.  Be prepared to handle $PREBUFFER
and other multi-line-input situations.
3/  Add your widget to the zle-line-finish hooks.  This is more likely
to play well with plugin managers and you don't need .accept-line, but
you still need to handle multi-line input.

All of these (except run-help) end up putting the whole command
including the appended pipeline into the history.  If you want to
avoid that, look at zshaddhistory hooks.

Naive/incomplete example of #3:

page-the-help() {
  if [[ -z $PREBUFFER && $BUFFER = *--help* ]]
  then RBUFFER+=" | less"
  fi
}
zle -N page-the-help
add-zle-hook-widget zle-line-finish page-the-help