Re: [RFC][PATCH] Reset ZLE hooks when changing prompt themes (was Re: [RFC][PATCH] `newuser` prompt theme)

[Marlon Richert <marlon.richert@xxxxxxxxx>]

On Sun, May 2, 2021 at 8:59 PM Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx> wrote:
>
> On Fri, Apr 16, 2021 at 3:38 PM Marlon Richert <marlon.richert@xxxxxxxxx> wrote:
> >
> > Attached is a new version of the patch that handles _all the things._ \o/
>
> This looks OK, with two questions:
> 1.  Subshells have been introduced.  Those won't be treated as
> interactive shells.

Are you sure about that? When I do `foo() { ( setopt ) }; foo`, it
still lists 'interactive' (though not 'monitor' or 'zle').

> Does that matter?

It doesn't appear to matter. The prompt previews look the same as
before. Try `prompt -p` (without further args). Doesn

> 2.  This bit in the restore style:
> +        $( add-zsh-hook -L )
> +        $( add-zle-hook-widget -L )
> There may not be anything to be done about this, but unless I'm
> mistaken that just re-adds all the previous hooks, it doesn't remove
> any?  The code it is replacing clobbered the entire list of precmd and
> preexec hooks, which I suppose also might also be wrong if anything
> other than the prompt theme was manipulating them.

`add-zsh-hook -L` outputs statements in the form of `typeset -g -a
<hook>_functions=( <func> ... )`, while `add-zle-hook-widget -L`
outputs statements in the form of `zstyle zle-<hook> widgets
<nr>:<widget> ...` (which is where add-zle-hook-widget stores the hook
widgets to call internally). eval'ing either of these results in the
same good, old-fashioned clobbering as in the old code. So, no
functional change there. :)

I just realized, though, that these lines (new and old) don't actually
do anything useful:
* When you call `prompt`, it will not unhook anything not called
`prompt_*_<hook>`. So, whatever hooks you've set up that don't follow
the naming scheme will still be there when you call `prompt restore`.
No need to restore them.
* When you call `prompt`, it will unhook everything called
`prompt_*_<hook>`. So, if a prompt theme correctly implements the
prompt system contract, its hook functions will already get unhooked
when switching themes. Again, no need to do anything special when
calling `prompt restore`.

The only case I can think of that would need special handling is if
you already had hooks installed that follow the `prompt_*_<hook>`
naming convention before calling `prompt` for the first time.

Should we just get rid of this part of the "restore" logic? And
instead just document clearly that `prompt` will auto-remove all hooks
that follow its naming scheme?


And speaking of prompt hooks and naming schemes:

On Fri, Apr 16, 2021 at 12:34 AM Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx> wrote:
> Marlon wrote on Thu, Apr 15, 2021 at 21:54:48 +0300:
> > On 14 Apr 2021, at 15:05, Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx> wrote:
> > >> +++ b/Functions/Prompts/promptinit
> > >> @@ -178,8 +177,13 @@ Use prompt -h <theme> for help on specific themes.'
> > >>
> > >>        # Reset some commonly altered bits to the default
> > >>        local hook
> > >> -       for hook in chpwd precmd preexec periodic zshaddhistory zshexit; do
> > >> -         add-zsh-hook -D "${hook}" "prompt_*_${hook}"
> > >> +       for hook in chpwd precmd preexec periodic zshaddhistory zshexit \
> > >> +           zsh_directory_name; do
> > >> +         add-zsh-hook -D "$hook" "prompt_*_$hook"
> > >> +       done
> > >> +       for hook in isearch-exit isearch-update line-pre-redraw line-init \
> > >> +           line-finish history-line-set keymap-select; do
> > >> +         add-zle-hook-widget -D "$hook" "prompt_*_$hook"
> > >
> > > Recommend to name these prompt_${foo}_bar-{isearch-exit,isearch-update,…,keymap-select}
> > > for some fixed value of «bar» to avoid namespace issues (i.e., name
> > > collisions between existing prompts and future hooks).
> >
> > Wouldn’t that be a breaking change in the API, though?
>
> No, it wouldn't, because those are add-zle-hook-widget hooks and the
> current API only deals with add-zsh-hook hooks.
>
> We could even recommend that add-zsh-hook hooks be named
> prompt_${foo}_baz_{chpwd,…} for some fixed value of baz.  We don't even
> have to change the code to support this (because the asterisk will match
> «${foo}_baz» just fine); we just need to document the recommendation and
> deprecate the previous recommended naming pattern.
>
> > Also, isn’t the prefix prompt_${foo}_ already a namespace of sorts? Why change this?
>
> What if the foo theme declares a function called prompt_foo_lorem (or
> even prompt_foo_ipsum_lorem) that _isn't_ an «add-*-hook lorem» hook
> function, and later we start to to auto-register functions matching the
> name pattern?
>
> Or if we were to make «add-zsh-hook bar lorem» and «add-zle-hook-widget
> bar ipsum» both valid, for a single value of bar, and a prompt theme
> wanted to install both hooks _and_ name the functions «lorem» and «ipsum»
> conventionally?
>
> Or if someone wanted to quickly grep for add-zle-hook-widget callbacks?

If we're going to change the prompt function naming scheme anyway, can
we change it to something that starts with . or _? Because then
`zstyle ':completion:*' prefix-needed yes` will conveniently hide
these.

How about .prompt.<theme>.<hook>? And then auto-register these
functions as hooks?

And should all of this go into the same patch? If `prompt`
automatically unregisters all hooks that follow a naming pattern
(regardless of how they've been registered), then I think it would
make sense for it to automatically register them, too.