Please give a look to the attached patch...

It adds two new values:

visible: to update when visible else do nothing (as Stefan suggested).

always: to always update or show completions (Like bash
show-all-if-ambiguous)

BTW: the lazy value is more like show-all-if-unmodified i think


On Wed, Mar 09, 2022 at 03:30:16PM +0100, Ergus wrote:
>On Wed, Mar 09, 2022 at 03:16:17PM +0200, Eli Zaretskii wrote:
>>>Date: Wed, 9 Mar 2022 12:46:54 +0100
>>>From: Ergus <spacibba@aol.com>
>>>Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
>>>
>>>Look at the attached patch, it may need some small improve to solve the
>>>case 4. but so far it gives a consistent behavior with any value of
>>>completion-auto-help (and it is actually simpler than the current code)
>>>
>>>Alternatively we may add another custom, something like:
>>>
>>>completions-on-complete-action which may have 3 possible values:
>>
>>We don't need a new option, we can add a new value to the
>>completion-auto-help.
>>
>>But yes, I think this behavior you propose _must_ be optional, most
>>probably opt-in for starters.  Not everyone will want it.
>>
>>See also completion-cycle-threshold: this new behavior should not
>>tramp that option.
>
>I tend to agree Eli, but actually I started a thread because the default
>behavior is indeed inconsistent with completion-auto-help as the same
>Stefan mentioned.
>
>The current behavior mixes the completion-auto-help==t with
>completion-auto-help=='lazy when there is some completion and the
>completions are already visible (hiding them).
>
>If we do:
>
>compi<tab> it should be completed, but if the completions list is
>somehow visible, then after the tab it is not correct, so we currently
>hide it, when we must just update it right?
>
>The fix in any case is extremely simple and I think that with a new vale
>for completion-auto-help to 'always it will work, but may be even
>complicated to explain in the documentation...
>
>