Re: [PATCH] `completing-read`: Add `group-function` support to completion metadata

[Daniel Mendler <mail@daniel-mendler.de>]

On 4/26/21 12:40 AM, Dmitry Gutov wrote:
> So it's better if at least icomplete-mode is enabled, preferably with an 
> option which shows the completions right away with no input. And the 
> vertical style should be even better.

I agree that Icomplete/Vertico/Ivy works better if you are selecting 
instead of completing. However if an extension like `group-function` is 
made to the completion metadata it should also be available by the 
default completion UI.

> Helm and Consult use it mostly for sources which return some sort of 
> "matches" from a Grep-like program, right? Lots of matches, none of them 
> knowable in advance? Stock Emacs usually uses a buffer for that use case 
> (like M-x rgrep).

No, Consult also offers commands, where you can know the matches in 
advance. For example I have these commands, which should satisfy your 
criterion:

* consult-org-agenda: Select headline (Grouped by file name)
* consult-imenu: Select imenu item (Grouped by type, function, variable etc)
* consult-buffer: Switch to recent files, buffers, bookmarks
* consult-mode-command: Invoke command associated with the current mode 
(Grouped in local/global minor-mode and major-mode)
* consult-minor-mode-menu: Toggle minor modes by name (Grouped by on/off 
local/global)

There are more commands which may fall more into the search category 
where you don't know exactly what you are looking for.

Note that there are also users who implemented small extensions for the 
default completion UI, e.g., such that the *Completions* buffers appears 
after a delay and a few characters of input. I believe Protesilaos 
Stavrou is doing that. For such UIs the *Completions* buffer is as fully 
capable as one of the aforementioned vertical minibuffer UIs.

Daniel