Re: PATCH v2 (complete): Implement zle -P

[Daniel Shahaf <d.s@daniel.shahaf.name>]

Peter Stephenson wrote on Tue, Sep 01, 2015 at 11:03:31 +0100:
> On Tue, 1 Sep 2015 11:50:27 +0200
> Oliver Kiddle <okiddle@yahoo.co.uk> wrote:
> > Mikael Magnusson wrote:
> > > Indeed, I'm not sure if a user can figure out which widgets are useful
> > > to override in this way.  Would it be more useful to just do what Wayne
> > > did originally and let zle -N take some flags that specify which specific
> > > flags the new widget should have after all? The advantage of this method
> > > is that if we add more flags, users can wrap those widgets without us
> > > remembering to add a new zle -N flag as well.
> > 
> > I think that approach is better than the prototypes.
> 
> I'd be inclined to think this is both clearer and more powerful, too.

The 'zle -P' form is nice when wrapping arbitrary widgets and wanting to
preserve their properties.  For example:

    zsh -f
    bindkey -e
    bkw-wrapper() { zle .backward-kill-word }
    zle -N backward-kill-word bkw-wrapper
    echo foo bar<^W><^W><^Y>

This results in "echo foo <CURSOR>", but in "echo foo bar <CURSOR>"
without the third line — because 'bkw-wrapper' lacks the ZLE_KILL flag
which backward-kill-word has.

When I wrap a built-in widget, I would rather just say "Make my widget
like that other widget" than enumerate all flags my widget requires;
but when I define a new widget from scratch, being able to enumerate all
flags my widgets required would be good.

So, in summary, I think both forms are useful: 'zle -P' is useful for
wrapping widgets and 'zle -f' for defining new ones.

Cheers,

Daniel

P.S. As a concrete example, in zsh-syntax-highlighting, the difference
in flags between a built-in widget and a user-defined wrapper thereof
leads to issues such as [1], where wrapping a widget causes it to change
behaviour: https://github.com/zsh-users/zsh-syntax-highlighting/issues/150
I believe using 'zle -P' to define the wrapper widget would immediately
solve that issue.