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

[Mikael Magnusson <mikachu@gmail.com>]

On Sun, Sep 6, 2015 at 11:50 AM, Daniel Shahaf <d.s@daniel.shahaf.name> wrote:
> 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.

You can believe it, but it's not the case. The code that handles most
of these flags first checks that the widget is internal, and not a
shell wrapper function. Some more changes would be needed to make this
work. The yank flag is the only one that does something useful at the
moment.

-- 
Mikael Magnusson