Re: Global Aliases, but as a function?

["Daniel Shahaf" <d.s@xxxxxxxxxxxxxxxxxx>]

Bart Schaefer wrote on Sat, 18 Dec 2021 22:40 +00:00:
> 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.)
>

One could have preexec() install wrapper functions that shadow the
command words of any simple command that has a «--help» argument.

I'm not sure whether or not that's preferable to the zle approaches.

Cheers,

Daniel

> 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